There is an error in the graphic with the 747 which accidentally still shows the weight in pounds as 172,000 pounds instead of the 904,000 pounds its supposed to be. 410,000 KG is correct though. It was accidentally carried over from the previous graphic from the 737.
This was my senior design project in the last semester of my aerospace engineering undergrad. We were tasked with designing an air-to-orbit rocket that would be launched from a modified U-2 (which we reverse-engineered the previous semester) carrying a payload to low Earth orbit. We were given full control over the parameters of the rocket, launch altitude, launch site and direction, with a focus on comparing how beneficial altitude delta was to the performance gains of launching at higher initial velocities. Our team was split into various disciplines (Performance, Aerodynamics, Structures, Controls, etc.) so we all had to work in tandem, cross-sharing data. Performance was my area. I used data and telemetry from other existing vehicles, like Orbital ATK's Pegasus, to validate my results. In the end, we established that air-launching definitely allowed for a performance gain, but the gains were obviously not linear with increasing altitude. There's a point where flying higher and higher wasn't really worthwhile. More importantly, though, we learned that initial velocity is where the true performance gains were at. Launch a rocket from a hypersonic platform and altitude is almost irrelevant. Now spend the next hour destroying your brain cells on all the reasons that such a feat would be nearly impossible...especially if you want your rocket to carry any kind of meaningful payload into LEO. [LOL]
How fast was the carrier? Were you also able to adjust those parameters? What if your rocket would launch from a mach 3 jet at 25 000 m? Which basically means rebuilding the SR-71, but with payload capacity.
I'll bite. Why couldn't you launch it from a hypersonic platform, like one drawn by a plate using steam or another compressible gas, from zero to hypersonic in a couple of hundred meters? I'm not talking something carrying human, just incompressible building materials. I'm pretty sure you could have such a platform with very finite and realistic values of pressure, and do in the hundred's of metric tonne a launch.
@@dyinglight7994 that would basically be firing the rocket out of a cannon, which given that there are artillery shells with electronics, it might be possible, if payload limiting?
Your closing statement was summarized by the opening with using a U-2 (modified or not). Launching an orbital lift rocket from a glider. Yeah, serious brain cell destruction for that analysis! It'd make more sense to strap wings, tanks and engines onto the rocket for early lift, then jettison the lot. With, of course, any failure in separation resulting in a mission, equipment and if present, crew loss. The closest we came to doing such a thing was two SRB's and fuel tank on the shuttle and we saw what baggage that brought along.
@@Secretlyanothername Tho, to be fair, the pros are easy to understand, some of the cons are a bit more nuanced. Tho, double granted, most of the cons are very obvious as well.
Yea, this leaves the question 'why do people keep trying it then'? I get why some billionaire thinks it seems like a good idea, but when you do the design study and the rocket turns out to perform no better than a ground launch one, why go ahead and actually build it?
Here's an idea. Why not use jet engines like a turbo boost in cars. Create two or four specially designed jet engines that independently attach to the outside of the rocket. Power the jets at launch to "essentially decrease the weight of the rocket" at take off. After reaching the right altitude the jets can then detach like boosters and parachute down, to be reused later. They would only need fuel for about 5 minutes, and if it can save 30% than it might be something.
After watching from your orange flight suit days, i can still say that every single video you put out is worth getting excited about. I cant tell you how much your content is appreciated and needed, especially for people that dont just watch rocket stuff everyday.
One of SpaceX's best skills was identifying low hanging fruit. Right now, fuel is a TINY cost of launching a rocket compared to the rocket itself. Now, 50 years from now, if we're reusing rockets hundreds of times without major overhauls, fuel might become a much more significant percentage of operating costs. Then, this idea might be worth revisiting, although probably using something like an SR71 big brother getting to Mach 3+ and 80k feet or more.
What about safety? As Tim said, this must have been nightmarish for the safety of the crew and the airframe (separation could be done over unpopulated area ofc)! I mean the insurance cost of the aircraft must have been ... astronomical! 😂
@@lxndrlbr yeah I’m sure the failure mode analysis was a nightmare. I’d love to read it. That said those very Pegasus rocket stages are loaded into 18 wheelers and traverse our US highways posing a risk of detonation in the event of a traffic collision. Every safety scenario is evaluated. The DOT approval usually is the most difficult part of the rocket manufacturing timeline. They let that Pegasus free fall for kind of a long time before ignition. That analysis would be interesting. How far away must the rocket be such that if it detonated at ignition the pilots are safe? Would shrapnel hit the plane? Dangerous business.
What about crew dragon? They sit on top of a rocket. Everything will be risky. Again why is he comparing the 747 and the complete rocket. Compare that to the payload faring.
@@ganeshanguruswamy7111 crew escape from a rocket has been well studied: a small rocket tower above the capsule or rockets embedded in or below the capsule can separate and take them away to parachute altitude. Unless you put ejector seats for the crew in the 747, I don't see them have the time and mobility to escape a disintegrated aircraft.
The air-fed booster engine concept at least removes sensitive biological components from the equation. To cut down on complexity from a turbine engine, just use fuel injected into aerodynamic pressure fed scramjet. They wouldn't work at launch time but you could throttle down or discard the launch engines and still get decent thrust once you are moving a few hundred m/s through the atmosphere. Appreciate it Tim. Great work as always.
are we talking about 3 stages before the Rocket stage? 1. turbine engine to get to the speed to start the ramjet 2. Ram jet to the speed to start the scramjet 3. scramjet
@@MusikCassettePerhaps it's possible develop some engine that can be used successively as a launch rocket AND ramjet AND scramjet, so you could combine those three stages into one stage before the rocket stage.
Yea But you want the engine at launch time. The time when a rocket is fast enough for scram jets AND the atmosphere is thick enough might be just a few seconds
Just off the top of my head, but this seems more complex and more costly (and possibly less reliable or at least unproven) compared to some strap-on solid fuel boosters.
One thing to add is that the Isp advantage would only be for the first stage, as later stages already operate in vacuum. And Isp is relatively unimportant on the first stage, since staging velocity is not very high. This is especially the case if you want to recover the first stage, as Falcon 9 does (and if you do propulsive landing, those engines have to operate at sea level or close to it.)
Yep, for the first stage the thrust and mass flow are much more important. It would make more sense just to increase a diameter of the first stage and add more cheap engines with a relatively slow exhaust velocity and use the transom pressure excess they create more effectively.
A couple more points you missed: 1) The ability to launch from anywhere is massively hamstrung by needing to meet all of the licensing and regulations for each and every new area. Launching from a fixed pad allows the red tape to be a lot more easily handled. 2) The small launch segment is basically dead, thanks to the likes of the Transporter missions. Companies like Rocket Lab, Relativity, and Firefly all see the writing on the wall and are pivoting to medium lift, but there's just no way for Virgin to do that with an air launch system.
Yes. Virgin Orbit only had two places where it was cleared to launch. That was not "anywhere". Part of relocating the 747 was to get it to an available airspace. The payload would have to have been moved launch zone too. There were only two launch zones ever used. This makes the claim that money was wasted by flying the 747 to the customer is not accurate. That might have happened once. It would have been the only launch form a place other than the Mojave complex. I read the the UK launch location made it easier to get the payload to the correct inclination.
@@MrAwyork "We bring the launch vehicle to you" was a key tenet of Virgin's original pitch. The point is that the business case never made much sense from the start.
hey tim i am 12 yr old from india, bangalore i have always loved your videos and they have taught me alot, thanks for fueling me to become an aspiring astronaut
Great video! I remember a 1980s air launch concept drawing with a Space Shuttle Main Engine mounted in the tail of the 747 carrier aircraft, to get extra boost and trajectory. Cool in concept, prohibitive in practicality and economics.
Variable geometry intake and nozzle would probably be my big gamble. One engine that transitions from ram jet, to scram jet, to pure rocket. Awesome video.
@@MichaelWinter-ss6lx Well just enough to optimize pressure. Basically make a simplified version of John Bucknell's NTTR rocket. Something like the SABRE engine is probably the most promising truly "next gen" launch tech.
Great Video Tim. I love the way you make things easy to understand for all. So glad I was able to meet you in Austin. That was a fantastic weekend. I hope to do it again next year.
Scaling up sometimes does fix problems. if you had a large enough, Mach 2-4 capable vehicle that can pitch up hard enough in high atmosphere to get the space vehicle to almost the right angle, it could breakeven, but of course the scale of maintenance and operations would be delicate to keep balanced. but even with that high cost, being able to eliminate 75% of a booster's job would be worth it. also keep in mind, MaxQ at higher altitudes is far less stressful, so the structure could be lighter but honestly, i don't think it would make sense for cargo, as for a manned or mixed mission, the abort procedures get a lot more flexible when you have wings or start far from the ground
Per the Pizza Analogy... Colin Furze recently made that work quite well... we just need to get him to make an Air Launch system. Then it would work great and be a huge advantage... LOL! 🤣 Love the video Tim and how well you can make these complex concepts easy to understand. Keep up the great work!
This was actually also the premise of a technology startup that wanted to drive pizza kitchens around in vans. Like most technology startups, once interest rates rose above zero percent and money became expensive again, they went incredibly bankrupt.
A lot of airlaunch and "flexible launch" concepts were based on the assumption that regular spaceports with proper pads and GSE would always be rare and expensive, so airlaunch would get payload off the ground faster by using abundant runway infrastructure. Improved availability of launchpads and cryogenic propellant is basically what killed airlaunch, which is why LauncherOne using RP-1/LOX was a fitting end point.
I remember having this idea (and thinking it was a novel approach) back in the late 90s. I sketched it out and then started doing some math and quickly realized it just doesn't pay off. Humbling experience.
@@derp8575 No. The Pegasus was privately developed so it wouldn't be classified but anything rocketry related is export-controlled. Payloads are almost always the thing that's classified.
Wait a stinking moment, I asked that question to @derekmcdonald2168, not you. Allow the OP to respond or STFU. LOL!!!! You will be waiting a looooooong time, LOL!!!@@efulmer8675
You just made a great argument for turning a 747 (or Antonov) into a stick plane with an H tail and mounting the rocket on top so it's fully supported pre-launch. You could fly rockets longer than the launch fuselage. The problem is people thinking too small 🙌😉
I hear the humour here, but honestly this sounds like something that might resemble an eventual solution. The issues mentioned here are all hypothetically solvable, with future ideas and future materials.
Yes. an Antonov, or H tailed 747 could have a rail down its back to fully support the vehicle and help in its deployment, as it rolled off the back. Also the rocket could be fueled and/or oxidisered (new word alert!) in air from a tanker aircraft, so Max take-off weight limits and stresses need not apply.
@@spamcrud5639 If you do both fuel and oxidizer by AAR, I would suggest using different methods for transferring the two. Perhaps flying boom for fuel and probe and drogue for oxidizer; you want to minimize chances for problems.
Take say the wings from an A380, redesign the bits between the wings to turn it into a flying wing that could mate to the rocket and remove as much unneeded structure as possible. Given the slop in places like the flight profile and dropping from test equipment, it doesn't seem completely far fetched, just who wants to pay to do it.
When you go to do Kerbal, I've found an interesting way to use jets. Vertical launch with a first stage of only J-404 Panthers (Enough to get TWR>1 with afterburners). Burn straight up, then come straight down and use retro-propulsion to land on the pad. The "flying launch pad" works in Kerbal because of its complete lack of refurbishment penalty when you Recover the full cost of the craft landing on the pad. You're only paying the price of fuel, which will be minimal and optimal using this method. And it's not even hard to do in vanilla. You get such an absurd amount of Delta V from the jets that the apogee is high enough that you can finish circularizing your orbital stage before the jet reenters the atmosphere.
You read my mind! Haha! I was thinking, why not make SRB style jet engines to help the first stage and ditch the aircraft altogether. I look forward to that next video!
Solid Rocket Boosters were prohibited from human space flight; for good reasons. After the moon missions, every cutdown in budget was meat with insane security breeches. The Challenger could have simply shut down a liquid booster and separate for landing. SRBs can't be shut down, once ignited. If at all, one could use small firework crackers for a rocket chair, like in _KungFu_ _Panda_
@@MichaelWinter-ss6lx Indeed, I have never been a fan of SRB’s, I referenced them only for the style of how they attach and function to give a kick off the ground. So… I meant replace them with liquid fueled air breathing jet engines. Banned? I know many countries will not use SRB’s for manned space flight because of the higher risks, but NASA decided once again that “it’ll be fine”, and they made the SRB’s even larger on SLS.
Using jet engines as boosters is a cool idea and this got me thinking, but it probably is not worth it. The F135 engine on an F-35 fighter makes about 20 tons of thrust (at sea level), it weighs about 2 tons and then you would need a pod to hold it and the fuel it needs so about 3 tons in total per engine. So about 17 tons of additional thrust. Jet engines are dependant on air pressure so thrust decreases rapidly with altitude so I wonder how high the jet booster could go before it is no longer helping at all. Also a single Merlin rocket engine makes 100 tons of thrust and a rockets thrust increases as air pressure decreases. So jet boosters are probably not great.
@Jatheus They aren’t dangerous. They do have drawbacks though. Cost seems to be one of them. I actually worked at ATK for a year assisting the inspectors for the boosters.
Thanks very much for explaining this in a common sense way. After I thought about it, and realized that the jet would only provide a small fraction of the final velocity needed, there's just no way an air to orbit launch can ever really work. This is a classic case of doing your homework carefully before investing, and what happens when you don't. Thanks for another great video.
I have always be fascinated by air launching... I always imagined a space plane that was carried by a large cargo air plane like how they once planned to use the mriya..
In the end, a launcher aircraft is needlessly complicated and imo, a technological dead end. I wonder if it would be simpler to just make a semi-space plane. A rocket that takes off like an airplane, with the first stage/boosters being jet engines. After enough altitude, it would drop its wings and engines and switch to rocket propulsion. Maybe you could increase efficiency even more by using hybrid ram/scramjets.
The SpaceShuttle2.0 was planned this way, but with _aero-spike_ engines, and of course not dropping its wings. How's it supposed to land without wings? Developement of the _aero-spikes_ lost its funding. NASA never even got into their first assignment. They're a dead weight on tax payers purse.
Thanks for this Tim. The Falcon 1 vs Launcher One was a nice choice for comparison. The cons of aircraft launch are pretty vast. About the only decent use case I think is for very small satellites with very cheap disposable rockets that need a very specific inclinations. Launch location flexibility is about the only good point really. It is no wonder that Virgin Orbit has shut down with no way to be competitive. Next up, why don't they just "SpinLaunch!". 😉
Scott Manley has done two, the first 5 years ago was "Tech Startup Wants $30M To Build A Space Catapult (or Slingatron?)" his quote as "I'm really skeptical of the whole thing", and the more recent one "Can Spinlaunch Throw Rockets Into Space?" now giving it a "It's not unrealistic that this could actually work... I'm quite impressed. I was really skeptical when I saw Spinlaunch initially..."
Adding high performance air breathing jet engines to the rocket, as a first stage booster, in a ring that can detach & fly back for reuse sounds like a great idea!
The other thing that reduces payload increase is presumably what amounts to gravity drag: the aircraft is doing a lot of flying to first get into the target orbit release, and effectively doing a lot of work at a near 1:1 thrust-weight ratio.
Three deep dive video suggestions: 1) the SERJ engine; 2) Black Horse, stage and a half to orbit; 3) attempts to orbit before sputnik, there were several.
@@MrCateagle According to my (very crude) calculations, if Skylon used the Black Horse flight profile, it could get 30 tonnes to LEO rather than 15. So, yeah. I have. Edit.. and what's more, the original black horse paper did too. Part of the estimation was about a mach 5.5 Black Horse. They estimated that 40% of the dry-mass would be payload with a mach 5.5 airbrushing blackhorse powered by hydro-lox.
The way to fix this is to stack multiple jumbo jets vertically. Air to air refuelling type hook ups can translate to a vertical cable joining them together, with springs and damping or intelligent winding drums to handle turbulence. Once they are flying as a unit, they make a fairly quick pass over a runway, where the upper stages are waiting on a souped-up truck. With telemetry, the two can rendezvous and fly the dangling cable to the rocket sling. The second stage might be a ramjet, or something fancier.
I'm working in a startup on a project very similar to the vehicle you put on the video cover; I think you should have focused more on systems similar to that, where the first stage is the air-carrier with its own detachable wings and air-breathing engine like the SABRE instead of the old design with an aircraft-launchpad-carrier systems.
I was wondering why this wasn't a thing. Seems silly to use an off-the-shelf aircraft with all of it's mass instead of creating a custom air breathing first stage.
You basically covered this, but: Saying that the fuel used getting off the ground is "wasted" ignores the fact that the rocket has still gained significant velocity in the process. I think the worst part is that you lose the ability to abort -- something that happens all too often -- since you can't light the engines until it's been dropped from the plane without risking destruction of the plane (and potential loss of life). Every abort scenario automatically becomes a loss of vehicle and payload. The risk of something going wrong before the rocket is released still can't be ignored, though, no matter how small it might be made. I do like the idea of adding air breathing boosters to a rocket in place of something like strap-on SRBs, especially if they were self-contained and could detach and pop out some little wings and automatically fly a RTLS for reuse! I wonder how much the cost of running and maintaining such a system would be compared to just building new SRBs each time, though.
maintainance cost. that engine requries a precooler that has thousands of nickle tubes pressurized with ulta-cold helium with wall thicknesses measured in micrometers, a counter rotating tip driven comperssor with a pressure ratio of 150:1, and an oxydizer system that can run equally with liquid oxygen and supercritical air (which have vastly diffrent properties even if the denisties are similar). I think it also needs a varieable throat plug nozzle, and it has the ramjets that also need maintainance. It's also size limited because it has to take off from a runway, so it can't be heavier than a 747 or C5
Would be fun to see you discuss the possibility of vertical engine air breathing stages too, since thats the obvious alternative to using a carrier aircraft.
Your detailed yet pragmatic approach is so refreshing. These videos are bringing advanced principles to us, and you and the team deserve high praise for this content. Keep 'em coming 🎉
I love these videos, because it takes a concept that from a 30 foot view seems like it makes complete sense and is an obvious choice, but then explains why the reality is exactly the opposite of what "common sense" would lead an otherwise smart person to believe.
I would try to fit it in a rear bay door of a large modified cargo plane so you can maximize this true size of the rocket without the air restance on the way up. Then throw some solid rocket boosters below the wings to help the plane pitch up and have the rocket drop out the rear of the plane at a better angle. And make it all remotely controlled.
Brilliant I loved it! What you can do versus what you can do at a certain price, in certain time, at a certain success percentage, is a whole other question.
I had an art book as a kid with paintings of all sorts of spacecraft, including the original plan to launch shuttle off a 747. I think budget cuts killed that, or perhaps the disadvantages of air launch in this video.
What about a mile long steep hill with a launcher. They could propably speed it up to 400mph, that could save at least 20% of fuel. Maybe using a magnet train?
Already addressed by Tim. Look for his video on "why don't they launch rockets from a mountain?" And with a first stage going about 5000 mph at MECO (typical for a Starlink launch), 400 mph represents about 1/(12.5^2) (1/156) of the total kinetic energy. So the fuel savings would be less than 1%. How are you launching it up the hill? You can't use the rocket itself with a mass driver, because rockets are largely made from non-magnetic materials (aluminum/lithium or stainless steel). So now you need a structure large enough to support the rocket, using either its own engines (like in "When Worlds Collide" or "Fireball XL-5") or some external force (like mass driver rings). And now you have all that additional structure to design and maintain ("structure is expensive, fuel is cheap" - Jerry Pournelle). That could work on the Moon (lower escape velocity, no need to use a hill), but for launching people it's useless. There's at least one guy working on launching with a hydrogen gas gun on a hillside (it would need a solid motor kick stage to get to orbital speed), but that would be good only for cargo that doesn't mind LOTS of Gs.
Fuel is cheap. Liquid oxygen is extremely cheap (it's the second cheapest industrial liquid, after water). Making things complex and difficult to save really cheap propellant is not a win.
@@caldodge your kinetic energie calculation is right but you forgot the simple rocket equation... you need much more propellant/energy to gain a bit more payload because you have to carry all the propellant as well. Thats why it is not as bad as you said.
Great video as usual! I believe the next monumental shift in getting things into orbit will be a space elevator. I did my thesis on the feasibility of a MEO space elevator and we are still a long way away from that.
I'd love a little calculation of what kind of weight/fuel savings it would give to have the catch tower of SpaceX give superheavy a little push. So ignition, release and then a little help from the catch arms.
I worked on the Scaled Composites Roc which we built for Stratolaunch Systems as an aerial launch platform. It was designed to launch a 500,000 lb rocket from 60,000 feet. Though I left the company before the aircraft was completed, even then we could tell that the concept was going to be obsolete before we even finished it. A 500,000 lb rocket is larger than needed for most satellites (which are getting smaller and smaller each generation) yet much too small to launch a man rated capsule. There simply isn’t a demand for the launch capability that airplane was designed to provide.
The Soviet Union before it collapsed floated the MAKS system that was a mini-shuttle on a mini-external tank that in turn were mounted and carried up in altitude by the AN-225 Mirya. And speaking of SpaceX, for a few years, they worked with Stratolaunch on launching the (now cancelled) Falcon 5 from the Roc.
It makes a big difference where on earth an orbit-bound launch occurs. For equatorial orbits, it's more efficient to launch near the equator; the launcher is already nearly 1,000km/per hour faster than at the poles.
Thank you for this clear and comprehensive analysis on this very counter intuitive topic. Having often to explain it, I can now use this video as reference 👍😁
Air breathing rocket engines are the real game changer. You get the benefits of not carrying the extra oxidizer for the atmospheric part of the journey without the logistical and structural complications.
yea, 5 to 10 years ago I was so sure air launching was a good solution that could work. Thank you for keeping our expectations realistic and in line with good engineering principles.
Maybe I’m oversimplifying way too much but the balloon idea looks interesting. Obviously not a single balloon, but suppose some sort of framework with multiple balloons and a vertical-hanging rocket below. Recall the Hindenburg was 800 ft long and I believe had a lifting capacity of about 500,000 lbs (this included the massive framework/structure, diesel engines, fuel, cargo, people, etc.), so there is a precedent of sorts for building something like this (in the 1930's no less). This balloons/framework gizmo could be made cheaply, maybe even disposable. Imagine a rocket peacefully floating off the earth and then when almost out of sight igniting its engine, the balloons/framework returning to be used again.
If I was building a launch system? I would build "Project Atlantis". Because I understand why CURRENT rocket engineering is all about compromises and the rocket equation is a harsh mistress... There's very often a way in engineering to have your cake and eat it too. If rocket equation makes things very hard, avoid it, sidestep the issue. Launch from a train going at 80km altitude and at orbital speeds already, use a little bit of hydrogen peroxide to circularize your orbit at the top, simple.
I always liked the idea of using a railgun that is stationed at the base of Mt Chimborazo in Equador and continues all the way up the side of the mountain. You can basically use it to replace the first stage of the rocket and use a second/third stage to get it up to orbit and circularize. This gives 3 main benefits: 1) Launching from the equator to gain a small boost from the rotation of the earth. 2) Since the "barrel" of the launcher is at the top of the mountain the rockets don't have to fire until the atmoshpheric pressure is 0.45 atm, reducing drag and allowing the optimization of nozzels. 3) With about 10 km of runway you could reach Mach 1.25 in 45 seconds with 1G of acceleration. Or Mach 3 in 20 seconds with 5G of acceleration (plus gravity) which would be ideal for carrying astronauts. For satalites you could easily go more like 25 G and reach mach 6 (SR-71 speeds). The project would be way too impractical to ever actaully happen, but still cool.
Excellent content. I've been mulling this question over for years. Thank you for your detailed and cogent explanation. I think you put this issue to bed fairly handily.
The problem is, every time someone has thought about launching a rocket from altitude, they automatically think it either must be flown up by a plane, or use something like a spaceplane. Instead people should be treating the stages as "atmospheric stages" and "exoatmospheric stages". With this in mind, we can start designing rockets who have "atmoshperic stages" for their first stages that use air breathing engines such as turboramjets, which are famously used on the SR-71 and the new hypersonic drone from Hermeus, the Quarterhorse. The first stage would have either solid or liquid fueled boosters augmented by turboramjets that work like a traditional turbofan engine but when high enough speeds are reached, are able to bypass air around the compressor stages and burn the high speed yet subsonic air, like a traditional ramjet. This is done with the use of a sophisticated nose cone that uses shockwaves to slow and compress the incoming air. This stage would be operable until around 80,000ft where it would be dropped like a normal stage, but could have wings or a vertical landing system like Falcon 9/Starship, where it can land using some leftover fuel. With the turboramjets being much easier to restart than a rocket, it would be practical to use them for the powered landing and employing small wings for a normal horizontal landing versus the harder vertical landing that required much more power/fuel and more advanced control systems. For the "wings" we can think out of the box as well, it doesn't have to be heavy, rigid mount, traditional wings we use on planes today. Instead something like a paraglider's parachute wing can be employed which could also reduce damage incase of power loss/engine failure by helping bring the stage down like a normal parachute landing.
1) Get rid of people in the lift planes. 2) Use single wing design 3) Fuel the rocket from the plane above clouds so that less material is needed to keep the rocket together. 4) put wings on the rocket so that a rocket/scram hybrid can bring the rocket to real speed before going up.
When multiple engineering teams settle upon the same solution, you have to figure that solution was the one that over all best met the design parameters. Engineers are about making things work.
Your content is as valuable as a college degree for some of which I’m great full to congeal this way. Thank you for your expertise. Value such as you share is rising the bar. Thanks
This is the one of two alternative methods of launching payloads to space that seem feasible using our current technology, the other one being building launch site far up in the mountains. Both have little sense from economic standpoint, but fact they get mentioned and asked about repeatedly is a testament, that we have drive to improve and hope for the future. There are others ways to assist payload extraction from gravity well, but all of them require building currently impossible superstructures: - using looped string (40-300 km long), that is pushed as mach 5+, rising up under its own tension. One can hook payloads to it, and it will get accelerated and thrown up into the space. - atmosphere-dipping cantilevered arm, floating at low earth orbit. It spins so fast each time it's 250 km long arm lowers itself into atmosphere, it stays nearly stationary versus ground. - space elevator All three require magic material (unbreakable, ultralight, ultra strong ribbon for the loop, ultra light, ultra strong unbreakable cable for the elevator and ultra strong, ultra light, low drag stiff material for the catapult), and are danger for everything around, and in case of elevator literally forbidding ANY other object from Earth's orbit, forever. So yeah, blasting explosive sticks from the surface is the most accessible way of going to space... :C
Great stuff as usual - and doesn't even touch on the fact that you can't as easily reuse a rocket like this (and I use 'easily' lightly there - Falcon 9 landing still puts tears in my engineering eyes). That wasn't a killer when they started these projects, but with Falcon 9 being the raging success that it has been, I can't imagine anyone starting a new non-reusable launch system today, other than for niche uses. Having infrastructure that just cycles the rocket right back to where it started is a game changer. Sure, you could try and catch it etc. - but doing that anywhere in the world just adds to the impracticality of the whole idea.
Yeah, but when will the competition try to catch up? Seems they're still caught in 2004. (Don't you see: it's impossible! ;•). VonBraun wanted to do research on reuseability in the '60s; (No, we are a rich country).
I got friends who are curious about space stuff and are constantly asking questions....Thanks to your "why don't we just," series.....and of course all your other episodes..... I know exactly how to answer them 🤟
My humble opinion, the best solution seems to be something in-between, which is a shuttle with Ramjet drones instead of boosters, those could detach from the shuttle before it gets out of the atmosphere and went back for another launch.
You´r absolutely right on your points But why use primarily passenger aircraft for this example? Cargo models would have been a much better reference imo
Stratolaunch had 2 major problems which could have been fixed in a redesign. 1… They were going to launch a SpaceX rocket but SpaceX backed out because stratolaunch held the rocket at only one point which meant the rocket would require strengthening. This could have been fixed by supporting the rocket at 2 points by appropriately connecting the 2 inner tails across the two fuselages and making it the second rocket support point. 2… Stratolaunch could only get the nose up 17 degrees. This was their biggest problem. The rocket would drop the vertical pitch below 17 degrees before it got above 17 degrees. This meant the rocket launched in the wrong vertical angle. They were planing on fixing this by adding some kind of expendable wings to the rocket to help it change direction quickly. There would be several ways to fix this problem of 17 vs 45 degrees pitch in a redesign. A new designed Stratolaunch would fix these problems and improve some other parameters. Aviation week magazine described a proposed 747 with a large rocket engine sticking out of the back (and that’s not near the best solution). I imagine a 3 Raptor rocket launched at 50 degrees 1400 mph at 100,000 feet would be a better configuration and get daily launches off with decent sized payloads with cost effective price per pound. I have no doubt China military will develop some form of air launched reusable rocket to release intercontinental range hypersonic glide weapons.
Stratolaunch ROC is now testing reusable hypersonic vehicles for US military. Talon-A had a successful test launch a few months ago. US successfully tested air launching ICBMs during the cold war. B-1 was capable of fitting the minuteman ICBM in its weapons bay before signing a treaty with Russia and having to split the weapons bay into two separate ones.
I had a thought going through my head watching this about gutting the 747 interior, housing the rocket on the inside, and launching out of the nose by having it open and close with an exhaust exit opening in the back of the 747, but the logistics of making that work, plus the safety issues make me twitch
The problem with Virgin Orbit was terrible management and lack of customer materialization. The heavy mass problem was something that was being addressed and would have gotten better over time.
There is an error in the graphic with the 747 which accidentally still shows the weight in pounds as 172,000 pounds instead of the 904,000 pounds its supposed to be. 410,000 KG is correct though. It was accidentally carried over from the previous graphic from the 737.
Fool!
Maybe just use SI units...instead of imperial...
@@112313 - But then the many 'Muricans who can't tell Treason from Reason might not understand. 😕
Tim - All very interesting, but when are you coming out with the video you previously mentioned, on maglev-assisted launch? @EverydayAstronaut
they do....
This was my senior design project in the last semester of my aerospace engineering undergrad. We were tasked with designing an air-to-orbit rocket that would be launched from a modified U-2 (which we reverse-engineered the previous semester) carrying a payload to low Earth orbit. We were given full control over the parameters of the rocket, launch altitude, launch site and direction, with a focus on comparing how beneficial altitude delta was to the performance gains of launching at higher initial velocities. Our team was split into various disciplines (Performance, Aerodynamics, Structures, Controls, etc.) so we all had to work in tandem, cross-sharing data. Performance was my area. I used data and telemetry from other existing vehicles, like Orbital ATK's Pegasus, to validate my results. In the end, we established that air-launching definitely allowed for a performance gain, but the gains were obviously not linear with increasing altitude. There's a point where flying higher and higher wasn't really worthwhile. More importantly, though, we learned that initial velocity is where the true performance gains were at. Launch a rocket from a hypersonic platform and altitude is almost irrelevant. Now spend the next hour destroying your brain cells on all the reasons that such a feat would be nearly impossible...especially if you want your rocket to carry any kind of meaningful payload into LEO. [LOL]
How fast was the carrier? Were you also able to adjust those parameters? What if your rocket would launch from a mach 3 jet at 25 000 m?
Which basically means rebuilding the SR-71, but with payload capacity.
My condolences to your struggles...
I'll bite. Why couldn't you launch it from a hypersonic platform, like one drawn by a plate using steam or another compressible gas, from zero to hypersonic in a couple of hundred meters?
I'm not talking something carrying human, just incompressible building materials.
I'm pretty sure you could have such a platform with very finite and realistic values of pressure, and do in the hundred's of metric tonne a launch.
@@dyinglight7994 that would basically be firing the rocket out of a cannon, which given that there are artillery shells with electronics, it might be possible, if payload limiting?
Your closing statement was summarized by the opening with using a U-2 (modified or not). Launching an orbital lift rocket from a glider.
Yeah, serious brain cell destruction for that analysis!
It'd make more sense to strap wings, tanks and engines onto the rocket for early lift, then jettison the lot. With, of course, any failure in separation resulting in a mission, equipment and if present, crew loss.
The closest we came to doing such a thing was two SRB's and fuel tank on the shuttle and we saw what baggage that brought along.
17:01 "Liftoff! Disregard."
A classic line.
I started this video like, "YEHH!?? WHY DON'T WE AIR LAUNCH??" and ended like "oh that's why"
Thanks buddy, good work o7
You can tell from the time stamps. 4 minutes about the pros of air-launch, and 14 minutes about the cons.
Yep - you were ready to swallow anything you were told to - don't attempt to understand it yourself.
@@Secretlyanothername Tho, to be fair, the pros are easy to understand, some of the cons are a bit more nuanced. Tho, double granted, most of the cons are very obvious as well.
Yea, this leaves the question 'why do people keep trying it then'? I get why some billionaire thinks it seems like a good idea, but when you do the design study and the rocket turns out to perform no better than a ground launch one, why go ahead and actually build it?
Here's an idea. Why not use jet engines like a turbo boost in cars. Create two or four specially designed jet engines that independently attach to the outside of the rocket. Power the jets at launch to "essentially decrease the weight of the rocket" at take off. After reaching the right altitude the jets can then detach like boosters and parachute down, to be reused later. They would only need fuel for about 5 minutes, and if it can save 30% than it might be something.
After watching from your orange flight suit days, i can still say that every single video you put out is worth getting excited about. I cant tell you how much your content is appreciated and needed, especially for people that dont just watch rocket stuff everyday.
Hah, would be kinda funny if he used it once again for a short video or something.
Or on his Dear Moon flight hahaha.@@CarlosAM1
I was thinking it would be cool to see Tim in his spacesuit again.
By the time Dear Moon is really a thing custom suit themes may also be a thing. That mission is all about art right :)
…new ground to earth expert
One of SpaceX's best skills was identifying low hanging fruit. Right now, fuel is a TINY cost of launching a rocket compared to the rocket itself. Now, 50 years from now, if we're reusing rockets hundreds of times without major overhauls, fuel might become a much more significant percentage of operating costs. Then, this idea might be worth revisiting, although probably using something like an SR71 big brother getting to Mach 3+ and 80k feet or more.
I worked on Pegasus in the 1990’s. We had a couple of stage separation issues early in the program but we solved those. Fun times.
What about safety? As Tim said, this must have been nightmarish for the safety of the crew and the airframe (separation could be done over unpopulated area ofc)! I mean the insurance cost of the aircraft must have been ... astronomical! 😂
@@lxndrlbr yeah I’m sure the failure mode analysis was a nightmare. I’d love to read it. That said those very Pegasus rocket stages are loaded into 18 wheelers and traverse our US highways posing a risk of detonation in the event of a traffic collision. Every safety scenario is evaluated. The DOT approval usually is the most difficult part of the rocket manufacturing timeline. They let that Pegasus free fall for kind of a long time before ignition. That analysis would be interesting. How far away must the rocket be such that if it detonated at ignition the pilots are safe? Would shrapnel hit the plane? Dangerous business.
What about crew dragon? They sit on top of a rocket. Everything will be risky. Again why is he comparing the 747 and the complete rocket. Compare that to the payload faring.
@@ganeshanguruswamy7111 crew escape from a rocket has been well studied: a small rocket tower above the capsule or rockets embedded in or below the capsule can separate and take them away to parachute altitude.
Unless you put ejector seats for the crew in the 747, I don't see them have the time and mobility to escape a disintegrated aircraft.
@@Zeett09Out the back of C-17/C-130s on reusable steered/powered pallets?
The air-fed booster engine concept at least removes sensitive biological components from the equation.
To cut down on complexity from a turbine engine, just use fuel injected into aerodynamic pressure fed scramjet. They wouldn't work at launch time but you could throttle down or discard the launch engines and still get decent thrust once you are moving a few hundred m/s through the atmosphere.
Appreciate it Tim. Great work as always.
are we talking about 3 stages before the Rocket stage?
1. turbine engine to get to the speed to start the ramjet
2. Ram jet to the speed to start the scramjet
3. scramjet
@@MusikCassettePerhaps it's possible develop some engine that can be used successively as a launch rocket AND ramjet AND scramjet, so you could combine those three stages into one stage before the rocket stage.
Yea
But you want the engine at launch time. The time when a rocket is fast enough for scram jets AND the atmosphere is thick enough might be just a few seconds
Just off the top of my head, but this seems more complex and more costly (and possibly less reliable or at least unproven) compared to some strap-on solid fuel boosters.
I guess that will be the answer for the whole Jet Engine idea anyway. But its interesting to think about the possibilities :D
One thing to add is that the Isp advantage would only be for the first stage, as later stages already operate in vacuum. And Isp is relatively unimportant on the first stage, since staging velocity is not very high. This is especially the case if you want to recover the first stage, as Falcon 9 does (and if you do propulsive landing, those engines have to operate at sea level or close to it.)
Did he even talk about "ISP"?
@@cube2foxSpecific impulse yes he did
Out the back of C-17/C-130s on reusable steered/powered pallets?
@@Crunch_dGH Only if you are a Rapid Dragon missile.
Yep, for the first stage the thrust and mass flow are much more important. It would make more sense just to increase a diameter of the first stage and add more cheap engines with a relatively slow exhaust velocity and use the transom pressure excess they create more effectively.
A couple more points you missed:
1) The ability to launch from anywhere is massively hamstrung by needing to meet all of the licensing and regulations for each and every new area. Launching from a fixed pad allows the red tape to be a lot more easily handled.
2) The small launch segment is basically dead, thanks to the likes of the Transporter missions. Companies like Rocket Lab, Relativity, and Firefly all see the writing on the wall and are pivoting to medium lift, but there's just no way for Virgin to do that with an air launch system.
Yes. Virgin Orbit only had two places where it was cleared to launch. That was not "anywhere". Part of relocating the 747 was to get it to an available airspace. The payload would have to have been moved launch zone too. There were only two launch zones ever used. This makes the claim that money was wasted by flying the 747 to the customer is not accurate. That might have happened once. It would have been the only launch form a place other than the Mojave complex. I read the the UK launch location made it easier to get the payload to the correct inclination.
@@MrAwyork "We bring the launch vehicle to you" was a key tenet of Virgin's original pitch. The point is that the business case never made much sense from the start.
hey tim i am 12 yr old from india, bangalore
i have always loved your videos and they have taught me alot,
thanks for fueling me to become an aspiring astronaut
Great video! I remember a 1980s air launch concept drawing with a Space Shuttle Main Engine mounted in the tail of the 747 carrier aircraft, to get extra boost and trajectory. Cool in concept, prohibitive in practicality and economics.
Why don't they fly the booster and starship to their pads on their own power instead of moving them down the street ;D
Cost of fuel
Are you serious or delirious
Because moving them down the street is cheap and effective.
@@Scooterdude01it was a joke. Look at emote at end.
@@just_archan sorry, I thought you were a Democrat.
Variable geometry intake and nozzle would probably be my big gamble. One engine that transitions from ram jet, to scram jet, to pure rocket. Awesome video.
Variable nozzle = _aero-spike_
@@MichaelWinter-ss6lx Well just enough to optimize pressure. Basically make a simplified version of John Bucknell's NTTR rocket. Something like the SABRE engine is probably the most promising truly "next gen" launch tech.
Much easier said then done.
The SR-71 used that concept to a serious degree - and had a lot of issues with the engines "flaming out".
With a variable geometry flying wing. Just to make things extra hard. Would be cool, but insane.
@@hypertectonics7009 F35 can change it's nozzle orientation by over 90 degrees... Variable intake goes all the way back to the MiG-21 from the 50s.
Pro’s of air launch explained in 3:50 minutes.
Con’s of air launching explained in 14 minutes.
Seems pretty clear why people don’t do it that much
Thanks!
Great Video Tim. I love the way you make things easy to understand for all. So glad I was able to meet you in Austin. That was a fantastic weekend. I hope to do it again next year.
Tim, you are a true national treasure/resource. Thanks for the work you put into these.
International treasure too.
Because the flamey end is pointed the wrong way! Duh
The Up-goer program has learned much from this concept.
Now there's a real rocket scientist!
Scaling up sometimes does fix problems. if you had a large enough, Mach 2-4 capable vehicle that can pitch up hard enough in high atmosphere to get the space vehicle to almost the right angle, it could breakeven, but of course the scale of maintenance and operations would be delicate to keep balanced. but even with that high cost, being able to eliminate 75% of a booster's job would be worth it.
also keep in mind, MaxQ at higher altitudes is far less stressful, so the structure could be lighter
but honestly, i don't think it would make sense for cargo, as for a manned or mixed mission, the abort procedures get a lot more flexible when you have wings or start far from the ground
Per the Pizza Analogy... Colin Furze recently made that work quite well... we just need to get him to make an Air Launch system. Then it would work great and be a huge advantage... LOL! 🤣
Love the video Tim and how well you can make these complex concepts easy to understand. Keep up the great work!
This was actually also the premise of a technology startup that wanted to drive pizza kitchens around in vans. Like most technology startups, once interest rates rose above zero percent and money became expensive again, they went incredibly bankrupt.
I was thinking the same thing!
Finally, you're back. Haven't been watching your videos (won't go into why), but, keep this up and I'll keep coming back.
Thank you, Tim (all everyone behind the scenes)!!! These videos are fantastic - Go Team Space!!!
A lot of airlaunch and "flexible launch" concepts were based on the assumption that regular spaceports with proper pads and GSE would always be rare and expensive, so airlaunch would get payload off the ground faster by using abundant runway infrastructure. Improved availability of launchpads and cryogenic propellant is basically what killed airlaunch, which is why LauncherOne using RP-1/LOX was a fitting end point.
11:59 💀
We nerd ksp2 blundrebirss🎉😮😅
Thanks!
I remember having this idea (and thinking it was a novel approach) back in the late 90s. I sketched it out and then started doing some math and quickly realized it just doesn't pay off. Humbling experience.
It did actually pay off for Orbital Sciences in the 1990s and 2000s. They launched the Pegasus (across three variants) 45 times.
@@efulmer8675 for small payloads, to low orbits. Not useful for much else
I actually work on Pegasus! What a great video AS ALWAYS
Is your work classified and compartmentalized?
@@derp8575 No. The Pegasus was privately developed so it wouldn't be classified but anything rocketry related is export-controlled. Payloads are almost always the thing that's classified.
Wait a stinking moment, I asked that question to @derekmcdonald2168, not you. Allow the OP to respond or STFU. LOL!!!! You will be waiting a looooooong time, LOL!!!@@efulmer8675
Are you Derek?@@efulmer8675
My reply was deleted, so I will reply again, are you @derek? I'll wait..........@@efulmer8675
Let's goooo! Another Tim deep-dive. I am all here for it!
Tim, great that you're making 'back to the basics' content that got me hooked in the first place!
Thanks so much for creating and sharing this informative and timely video. Great job. Keep it up.
As usual a well laid out arguement with lots of "oh, I guess so" moments. Thanks Tim.
You just made a great argument for turning a 747 (or Antonov) into a stick plane with an H tail and mounting the rocket on top so it's fully supported pre-launch. You could fly rockets longer than the launch fuselage. The problem is people thinking too small 🙌😉
I hear the humour here, but honestly this sounds like something that might resemble an eventual solution. The issues mentioned here are all hypothetically solvable, with future ideas and future materials.
Consider using an AN225 or equivalent for air launching.
Yes. an Antonov, or H tailed 747 could have a rail down its back to fully support the vehicle and help in its deployment, as it rolled off the back.
Also the rocket could be fueled and/or oxidisered (new word alert!) in air from a tanker aircraft, so Max take-off weight limits and stresses need not apply.
@@spamcrud5639 If you do both fuel and oxidizer by AAR, I would suggest using different methods for transferring the two. Perhaps flying boom for fuel and probe and drogue for oxidizer; you want to minimize chances for problems.
Take say the wings from an A380, redesign the bits between the wings to turn it into a flying wing that could mate to the rocket and remove as much unneeded structure as possible. Given the slop in places like the flight profile and dropping from test equipment, it doesn't seem completely far fetched, just who wants to pay to do it.
When you go to do Kerbal, I've found an interesting way to use jets. Vertical launch with a first stage of only J-404 Panthers (Enough to get TWR>1 with afterburners). Burn straight up, then come straight down and use retro-propulsion to land on the pad. The "flying launch pad" works in Kerbal because of its complete lack of refurbishment penalty when you Recover the full cost of the craft landing on the pad. You're only paying the price of fuel, which will be minimal and optimal using this method. And it's not even hard to do in vanilla. You get such an absurd amount of Delta V from the jets that the apogee is high enough that you can finish circularizing your orbital stage before the jet reenters the atmosphere.
Tim, thanks for putting out this video, always have loved your features, learned so much from you!
Thanks! These videos are super helpful and add context for first principles thought experiments. Lots of comparisons I was unaware of
Hi Tim, great reaserch. Looking forward to part two. Yours, everyday person.
Why don't we teleport the rockets into space and then launch them? Your next vid please.
You read my mind! Haha! I was thinking, why not make SRB style jet engines to help the first stage and ditch the aircraft altogether. I look forward to that next video!
Solid Rocket Boosters were prohibited from human space flight; for good reasons. After the moon missions, every cutdown in budget was meat with insane security breeches.
The Challenger could have simply shut down a liquid booster and separate for landing. SRBs can't be shut down, once ignited. If at all, one could use small firework crackers for a rocket chair, like in _KungFu_ _Panda_
@@MichaelWinter-ss6lx Indeed, I have never been a fan of SRB’s, I referenced them only for the style of how they attach and function to give a kick off the ground. So… I meant replace them with liquid fueled air breathing jet engines.
Banned? I know many countries will not use SRB’s for manned space flight because of the higher risks, but NASA decided once again that “it’ll be fine”, and they made the SRB’s even larger on SLS.
Using jet engines as boosters is a cool idea and this got me thinking, but it probably is not worth it. The F135 engine on an F-35 fighter makes about 20 tons of thrust (at sea level), it weighs about 2 tons and then you would need a pod to hold it and the fuel it needs so about 3 tons in total per engine. So about 17 tons of additional thrust. Jet engines are dependant on air pressure so thrust decreases rapidly with altitude so I wonder how high the jet booster could go before it is no longer helping at all. Also a single Merlin rocket engine makes 100 tons of thrust and a rockets thrust increases as air pressure decreases. So jet boosters are probably not great.
@MichaelWinter-ss6lx
Solids are perfect but using challenger as an example is ridiculous. The problem was fixed.
@Jatheus
They aren’t dangerous. They do have drawbacks though. Cost seems to be one of them.
I actually worked at ATK for a year assisting the inspectors for the boosters.
Thanks very much for explaining this in a common sense way. After I thought about it, and realized that the jet would only provide a small fraction of the final velocity needed, there's just no way an air to orbit launch can ever really work. This is a classic case of doing your homework carefully before investing, and what happens when you don't. Thanks for another great video.
I have always be fascinated by air launching... I always imagined a space plane that was carried by a large cargo air plane like how they once planned to use the mriya..
In the end, a launcher aircraft is needlessly complicated and imo, a technological dead end.
I wonder if it would be simpler to just make a semi-space plane. A rocket that takes off like an airplane, with the first stage/boosters being jet engines. After enough altitude, it would drop its wings and engines and switch to rocket propulsion.
Maybe you could increase efficiency even more by using hybrid ram/scramjets.
@@VikingTeddy A plane capable of going suborbital on it's own, and thus becoming the entire first stage on it's own?
Launching only the "upper stage."
The SpaceShuttle2.0 was planned this way, but with _aero-spike_ engines, and of course not dropping its wings. How's it supposed to land without wings? Developement of the _aero-spikes_ lost its funding.
NASA never even got into their first assignment. They're a dead weight on tax payers purse.
@@VikingTeddy yes, and an ion engine for the final stage
@@VikingTeddy All's it takes is 💲💲 .
Thanks for this Tim. The Falcon 1 vs Launcher One was a nice choice for comparison. The cons of aircraft launch are pretty vast. About the only decent use case I think is for very small satellites with very cheap disposable rockets that need a very specific inclinations. Launch location flexibility is about the only good point really. It is no wonder that Virgin Orbit has shut down with no way to be competitive. Next up, why don't they just "SpinLaunch!". 😉
Scott Manley has done two, the first 5 years ago was "Tech Startup Wants $30M To Build A Space Catapult (or Slingatron?)" his quote as "I'm really skeptical of the whole thing", and the more recent one "Can Spinlaunch Throw Rockets Into Space?" now giving it a "It's not unrealistic that this could actually work... I'm quite impressed. I was really skeptical when I saw Spinlaunch initially..."
Adding high performance air breathing jet engines to the rocket, as a first stage booster, in a ring that can detach & fly back for reuse sounds like a great idea!
The other thing that reduces payload increase is presumably what amounts to gravity drag: the aircraft is doing a lot of flying to first get into the target orbit release, and effectively doing a lot of work at a near 1:1 thrust-weight ratio.
Three deep dive video suggestions: 1) the SERJ engine; 2) Black Horse, stage and a half to orbit; 3) attempts to orbit before sputnik, there were several.
Also, a track-and-ramp launch like the old children's TV show Fireball XL5
. That goes all the way back to Sanger's Silbervogel concept.
Consider a combination of Black Horse with a hypersonic air-breather as a SSTO vehicle.
@@MrCateagle
According to my (very crude) calculations, if Skylon used the Black Horse flight profile, it could get 30 tonnes to LEO rather than 15.
So, yeah. I have.
Edit.. and what's more, the original black horse paper did too. Part of the estimation was about a mach 5.5 Black Horse. They estimated that 40% of the dry-mass would be payload with a mach 5.5 airbrushing blackhorse powered by hydro-lox.
The way to fix this is to stack multiple jumbo jets vertically. Air to air refuelling type hook ups can translate to a vertical cable joining them together, with springs and damping or intelligent winding drums to handle turbulence. Once they are flying as a unit, they make a fairly quick pass over a runway, where the upper stages are waiting on a souped-up truck. With telemetry, the two can rendezvous and fly the dangling cable to the rocket sling. The second stage might be a ramjet, or something fancier.
I'm working in a startup on a project very similar to the vehicle you put on the video cover; I think you should have focused more on systems similar to that, where the first stage is the air-carrier with its own detachable wings and air-breathing engine like the SABRE instead of the old design with an aircraft-launchpad-carrier systems.
Can you share the name of the startup?
Thunderbirds "Zero-X"? 🤣
@@peps9839 It’s called Rocketech Systems
I was wondering why this wasn't a thing. Seems silly to use an off-the-shelf aircraft with all of it's mass instead of creating a custom air breathing first stage.
Yeah the thumbnail is really misleading. Would have been a more interesting topic.
You basically covered this, but: Saying that the fuel used getting off the ground is "wasted" ignores the fact that the rocket has still gained significant velocity in the process.
I think the worst part is that you lose the ability to abort -- something that happens all too often -- since you can't light the engines until it's been dropped from the plane without risking destruction of the plane (and potential loss of life). Every abort scenario automatically becomes a loss of vehicle and payload.
The risk of something going wrong before the rocket is released still can't be ignored, though, no matter how small it might be made.
I do like the idea of adding air breathing boosters to a rocket in place of something like strap-on SRBs, especially if they were self-contained and could detach and pop out some little wings and automatically fly a RTLS for reuse! I wonder how much the cost of running and maintaining such a system would be compared to just building new SRBs each time, though.
What about the Skylon spaceplane concept? A jetengine that turns itself into a rocket engine at higher altitudes. Single-stage-to-orbit
It bothers me how overlooked skylon is. Its potential is collosal.
maintainance cost.
that engine requries a precooler that has thousands of nickle tubes pressurized with ulta-cold helium with wall thicknesses measured in micrometers, a counter rotating tip driven comperssor with a pressure ratio of 150:1, and an oxydizer system that can run equally with liquid oxygen and supercritical air (which have vastly diffrent properties even if the denisties are similar). I think it also needs a varieable throat plug nozzle, and it has the ramjets that also need maintainance.
It's also size limited because it has to take off from a runway, so it can't be heavier than a 747 or C5
It would have tl start as a small sat launcher.@AKbamoida
Extremely limited payload capacity from everything I've seen. It has its niche, but it will never be a replacement for traditional rockets.
too complex and too much dry mass... single stage to orbit is not practical with traditional propulsion methods...
Really good breakdown, keep this series going, it's interesting to know why some things don't work.
But the one scenario that wasn't addressed, was the method used to launch ICBMs from a C-5
Would be fun to see you discuss the possibility of vertical engine air breathing stages too, since thats the obvious alternative to using a carrier aircraft.
Your detailed yet pragmatic approach is so refreshing. These videos are bringing advanced principles to us, and you and the team deserve high praise for this content.
Keep 'em coming 🎉
I love these videos, because it takes a concept that from a 30 foot view seems like it makes complete sense and is an obvious choice, but then explains why the reality is exactly the opposite of what "common sense" would lead an otherwise smart person to believe.
I would try to fit it in a rear bay door of a large modified cargo plane so you can maximize this true size of the rocket without the air restance on the way up. Then throw some solid rocket boosters below the wings to help the plane pitch up and have the rocket drop out the rear of the plane at a better angle. And make it all remotely controlled.
Brilliant I loved it! What you can do versus what you can do at a certain price, in certain time, at a certain success percentage, is a whole other question.
Well done, Tim. Videos like this one are why I became a Patreon sponsor a couple years ago.
I had an art book as a kid with paintings of all sorts of spacecraft, including the original plan to launch shuttle off a 747. I think budget cuts killed that, or perhaps the disadvantages of air launch in this video.
What about the additional drag induced by the missing doors?
Nice and clean educative video. You've improved your presenting a lot! :)
What about a mile long steep hill with a launcher. They could propably speed it up to 400mph, that could save at least 20% of fuel.
Maybe using a magnet train?
a train/cannon is a good idea, but on the moon where there is no air resistance and low orbital velocity
Already addressed by Tim. Look for his video on "why don't they launch rockets from a mountain?" And with a first stage going about 5000 mph at MECO (typical for a Starlink launch), 400 mph represents about 1/(12.5^2) (1/156) of the total kinetic energy. So the fuel savings would be less than 1%.
How are you launching it up the hill? You can't use the rocket itself with a mass driver, because rockets are largely made from non-magnetic materials (aluminum/lithium or stainless steel). So now you need a structure large enough to support the rocket, using either its own engines (like in "When Worlds Collide" or "Fireball XL-5") or some external force (like mass driver rings). And now you have all that additional structure to design and maintain ("structure is expensive, fuel is cheap" - Jerry Pournelle).
That could work on the Moon (lower escape velocity, no need to use a hill), but for launching people it's useless. There's at least one guy working on launching with a hydrogen gas gun on a hillside (it would need a solid motor kick stage to get to orbital speed), but that would be good only for cargo that doesn't mind LOTS of Gs.
Fuel is cheap. Liquid oxygen is extremely cheap (it's the second cheapest industrial liquid, after water). Making things complex and difficult to save really cheap propellant is not a win.
@@pauldietz1325 there is a weight limit? Would you rather take more fuel or food?
@@caldodge your kinetic energie calculation is right but you forgot the simple rocket equation... you need much more propellant/energy to gain a bit more payload because you have to carry all the propellant as well. Thats why it is not as bad as you said.
Great video as usual!
I believe the next monumental shift in getting things into orbit will be a space elevator.
I did my thesis on the feasibility of a MEO space elevator and we are still a long way away from that.
Gotta say I really enjoy the topics and the simple (for non-tech guys like me) explanations that cover complex topics, well done.
I'd love a little calculation of what kind of weight/fuel savings it would give to have the catch tower of SpaceX give superheavy a little push. So ignition, release and then a little help from the catch arms.
Best plan is to build the Death Star first and launch from there. Simple.
The Empire approves!
I worked on the Scaled Composites Roc which we built for Stratolaunch Systems as an aerial launch platform. It was designed to launch a 500,000 lb rocket from 60,000 feet. Though I left the company before the aircraft was completed, even then we could tell that the concept was going to be obsolete before we even finished it. A 500,000 lb rocket is larger than needed for most satellites (which are getting smaller and smaller each generation) yet much too small to launch a man rated capsule. There simply isn’t a demand for the launch capability that airplane was designed to provide.
20:37 I forgot that starship actually flew 😂
And also how beautiful it is
Thanks, Tim. Nice job and great illustrations and videos.
The Soviet Union before it collapsed floated the MAKS system that was a mini-shuttle on a mini-external tank that in turn were mounted and carried up in altitude by the AN-225 Mirya.
And speaking of SpaceX, for a few years, they worked with Stratolaunch on launching the (now cancelled) Falcon 5 from the Roc.
Awesome Classic EDA video, Thanks Tim and Team
Pointy end front, flamey end back!
Well done Tim. Really interesting and educational.
Space elevator.2042
4:58 thanks for showing Mojave. It's been quite some time since I've been there.
It makes a big difference where on earth an orbit-bound launch occurs. For equatorial orbits, it's more efficient to launch near the equator; the launcher is already nearly 1,000km/per hour faster than at the poles.
Thank you for this clear and comprehensive analysis on this very counter intuitive topic. Having often to explain it, I can now use this video as reference 👍😁
0:18 - The last flying Lockheed L 10 11 Tristar 🤗
Air breathing rocket engines are the real game changer. You get the benefits of not carrying the extra oxidizer for the atmospheric part of the journey without the logistical and structural complications.
yea, 5 to 10 years ago I was so sure air launching was a good solution that could work. Thank you for keeping our expectations realistic and in line with good engineering principles.
Maybe I’m oversimplifying way too much but the balloon idea looks interesting. Obviously not a single balloon, but suppose some sort of framework with multiple balloons and a vertical-hanging rocket below.
Recall the Hindenburg was 800 ft long and I believe had a lifting capacity of about 500,000 lbs (this included the massive framework/structure, diesel engines, fuel, cargo, people, etc.), so there is a precedent of sorts for building something like this (in the 1930's no less).
This balloons/framework gizmo could be made cheaply, maybe even disposable. Imagine a rocket peacefully floating off the earth and then when almost out of sight igniting its engine, the balloons/framework returning to be used again.
1km vertical deep tunnel that accelerates the rocket before surfacing and letting go, giving it a free launch speed
If I was building a launch system? I would build "Project Atlantis".
Because I understand why CURRENT rocket engineering is all about compromises and the rocket equation is a harsh mistress...
There's very often a way in engineering to have your cake and eat it too. If rocket equation makes things very hard, avoid it, sidestep the issue.
Launch from a train going at 80km altitude and at orbital speeds already, use a little bit of hydrogen peroxide to circularize your orbit at the top, simple.
I always liked the idea of using a railgun that is stationed at the base of Mt Chimborazo in Equador and continues all the way up the side of the mountain. You can basically use it to replace the first stage of the rocket and use a second/third stage to get it up to orbit and circularize.
This gives 3 main benefits:
1) Launching from the equator to gain a small boost from the rotation of the earth.
2) Since the "barrel" of the launcher is at the top of the mountain the rockets don't have to fire until the atmoshpheric pressure is 0.45 atm, reducing drag and allowing the optimization of nozzels.
3) With about 10 km of runway you could reach Mach 1.25 in 45 seconds with 1G of acceleration. Or Mach 3 in 20 seconds with 5G of acceleration (plus gravity) which would be ideal for carrying astronauts. For satalites you could easily go more like 25 G and reach mach 6 (SR-71 speeds).
The project would be way too impractical to ever actaully happen, but still cool.
You might enjoy reading The Moon is a Harsh Mistress. It explores this very concept.
@@JohnFlower-NZ
I've read that, it was pretty good.
Do it
We missed you, Tim. Great video, as always!
Excellent content. I've been mulling this question over for years. Thank you for your detailed and cogent explanation. I think you put this issue to bed fairly handily.
The problem is, every time someone has thought about launching a rocket from altitude, they automatically think it either must be flown up by a plane, or use something like a spaceplane. Instead people should be treating the stages as "atmospheric stages" and "exoatmospheric stages". With this in mind, we can start designing rockets who have "atmoshperic stages" for their first stages that use air breathing engines such as turboramjets, which are famously used on the SR-71 and the new hypersonic drone from Hermeus, the Quarterhorse. The first stage would have either solid or liquid fueled boosters augmented by turboramjets that work like a traditional turbofan engine but when high enough speeds are reached, are able to bypass air around the compressor stages and burn the high speed yet subsonic air, like a traditional ramjet. This is done with the use of a sophisticated nose cone that uses shockwaves to slow and compress the incoming air. This stage would be operable until around 80,000ft where it would be dropped like a normal stage, but could have wings or a vertical landing system like Falcon 9/Starship, where it can land using some leftover fuel. With the turboramjets being much easier to restart than a rocket, it would be practical to use them for the powered landing and employing small wings for a normal horizontal landing versus the harder vertical landing that required much more power/fuel and more advanced control systems. For the "wings" we can think out of the box as well, it doesn't have to be heavy, rigid mount, traditional wings we use on planes today. Instead something like a paraglider's parachute wing can be employed which could also reduce damage incase of power loss/engine failure by helping bring the stage down like a normal parachute landing.
1) Get rid of people in the lift planes.
2) Use single wing design
3) Fuel the rocket from the plane above clouds so that less material is needed to keep the rocket together.
4) put wings on the rocket so that a rocket/scram hybrid can bring the rocket to real speed before going up.
When multiple engineering teams settle upon the same solution, you have to figure that solution was the one that over all best met the design parameters. Engineers are about making things work.
Your content is as valuable as a college degree for some of which I’m great full to congeal this way. Thank you for your expertise. Value such as you share is rising the bar. Thanks
This is the one of two alternative methods of launching payloads to space that seem feasible using our current technology, the other one being building launch site far up in the mountains. Both have little sense from economic standpoint, but fact they get mentioned and asked about repeatedly is a testament, that we have drive to improve and hope for the future.
There are others ways to assist payload extraction from gravity well, but all of them require building currently impossible superstructures:
- using looped string (40-300 km long), that is pushed as mach 5+, rising up under its own tension. One can hook payloads to it, and it will get accelerated and thrown up into the space.
- atmosphere-dipping cantilevered arm, floating at low earth orbit. It spins so fast each time it's 250 km long arm lowers itself into atmosphere, it stays nearly stationary versus ground.
- space elevator
All three require magic material (unbreakable, ultralight, ultra strong ribbon for the loop, ultra light, ultra strong unbreakable cable for the elevator and ultra strong, ultra light, low drag stiff material for the catapult), and are danger for everything around, and in case of elevator literally forbidding ANY other object from Earth's orbit, forever.
So yeah, blasting explosive sticks from the surface is the most accessible way of going to space... :C
I think you are right; the complexity and safety concerns way outweigh any potential pros of air launching.
Great stuff as usual - and doesn't even touch on the fact that you can't as easily reuse a rocket like this (and I use 'easily' lightly there - Falcon 9 landing still puts tears in my engineering eyes). That wasn't a killer when they started these projects, but with Falcon 9 being the raging success that it has been, I can't imagine anyone starting a new non-reusable launch system today, other than for niche uses. Having infrastructure that just cycles the rocket right back to where it started is a game changer. Sure, you could try and catch it etc. - but doing that anywhere in the world just adds to the impracticality of the whole idea.
Yeah, but when will the competition try to catch up? Seems they're still caught in 2004. (Don't you see: it's impossible! ;•).
VonBraun wanted to do research on reuseability in the '60s; (No, we are a rich country).
I got friends who are curious about space stuff and are constantly asking questions....Thanks to your "why don't we just," series.....and of course all your other episodes..... I know exactly how to answer them 🤟
My humble opinion, the best solution seems to be something in-between, which is a shuttle with Ramjet drones instead of boosters, those could detach from the shuttle before it gets out of the atmosphere and went back for another launch.
Thanks Tim, this is really informative. Maybe you can talk about launches from water, water platforms in some next episode.
You´r absolutely right on your points
But why use primarily passenger aircraft for this example? Cargo models would have been a much better reference imo
I really love this format!
Stratolaunch had 2 major problems which could have been fixed in a redesign.
1… They were going to launch a SpaceX rocket but SpaceX backed out because stratolaunch held the rocket at only one point which meant the rocket would require strengthening. This could have been fixed by supporting the rocket at 2 points by appropriately connecting the 2 inner tails across the two fuselages and making it the second rocket support point.
2… Stratolaunch could only get the nose up 17 degrees. This was their biggest problem. The rocket would drop the vertical pitch below 17 degrees before it got above 17 degrees. This meant the rocket launched in the wrong vertical angle. They were planing on fixing this by adding some kind of expendable wings to the rocket to help it change direction quickly. There would be several ways to fix this problem of 17 vs 45 degrees pitch in a redesign.
A new designed Stratolaunch would fix these problems and improve some other parameters. Aviation week magazine described a proposed 747 with a large rocket engine sticking out of the back (and that’s not near the best solution). I imagine a 3 Raptor rocket launched at 50 degrees 1400 mph at 100,000 feet would be a better configuration and get daily launches off with decent sized payloads with cost effective price per pound. I have no doubt China military will develop some form of air launched reusable rocket to release intercontinental range hypersonic glide weapons.
Stratolaunch ROC is now testing reusable hypersonic vehicles for US military. Talon-A had a successful test launch a few months ago. US successfully tested air launching ICBMs during the cold war. B-1 was capable of fitting the minuteman ICBM in its weapons bay before signing a treaty with Russia and having to split the weapons bay into two separate ones.
I had a thought going through my head watching this about gutting the 747 interior, housing the rocket on the inside, and launching out of the nose by having it open and close with an exhaust exit opening in the back of the 747, but the logistics of making that work, plus the safety issues make me twitch
The problem with Virgin Orbit was terrible management and lack of customer materialization. The heavy mass problem was something that was being addressed and would have gotten better over time.