There are all sorts of advantages of a concept like this. Right now there are very few good airlaunching aircraft options. Existing planes all force you to very narrow body diameters, and custom planes are rarely cost effective unless there are other users (ie LauncherOne benefits a lot from having SS2 provide most of the demand for WK2, so it only has to buy flights "by the drink"). This gives you the benefit of a custom aircraft at a much lower price, and could likely scale up to nearly stratolaunch sizes.Also, because it's unmanned, zoom climbs like they show provide a huge flight-path-angle advantage. Staging subsonic at high altitude and a good flight path angle can knock your remaining dV to orbit down to around 8km/s (from a typical 9600m/s for ground launch).The one thing I don't get is why they do a drop-and-light. They'd be better off lighting the rocket, and using it for the pitchup maneuver--that way you can verify the rocket engine is working before you release it from the glider. I guess if that rocket is a solid booster, you don't want to light a firecracker off attached to your vehicle, but if it's a liquid fueled system, lighting it and using it for the pitchup thrust is a great way of doing the equivalence of SpaceX's pre-launch hold-downs. But all told, this is a really neat concept, even if I have minor quibbles about a few design choices. I actually had been wanting to do something like this for a proposed effort a few years ago, so glad someone else did it first.~Jon
Quote from: jongoff on 02/03/2015 07:42 pmThere are all sorts of advantages of a concept like this. Right now there are very few good airlaunching aircraft options. Existing planes all force you to very narrow body diameters, and custom planes are rarely cost effective unless there are other users (ie LauncherOne benefits a lot from having SS2 provide most of the demand for WK2, so it only has to buy flights "by the drink"). This gives you the benefit of a custom aircraft at a much lower price, and could likely scale up to nearly stratolaunch sizes.Also, because it's unmanned, zoom climbs like they show provide a huge flight-path-angle advantage. Staging subsonic at high altitude and a good flight path angle can knock your remaining dV to orbit down to around 8km/s (from a typical 9600m/s for ground launch).The one thing I don't get is why they do a drop-and-light. They'd be better off lighting the rocket, and using it for the pitchup maneuver--that way you can verify the rocket engine is working before you release it from the glider. I guess if that rocket is a solid booster, you don't want to light a firecracker off attached to your vehicle, but if it's a liquid fueled system, lighting it and using it for the pitchup thrust is a great way of doing the equivalence of SpaceX's pre-launch hold-downs. But all told, this is a really neat concept, even if I have minor quibbles about a few design choices. I actually had been wanting to do something like this for a proposed effort a few years ago, so glad someone else did it first.~JonI don't see the real benefit of this. You still need to make a custom carrier aircraft / drone, and now you have converted a relatively simple air launch concept into one that requires TWO stages before the rocket even is dropped (the aircraft pulling, then the carrier)And scaling this up would be difficult - but that is a problem shared with all air launch concepts.
Why not place two turbofans over each fusalage and make do without the tow? But that's just me...
Quote from: Lars-J on 02/03/2015 11:27 pmI don't see the real benefit of this. You still need to make a custom carrier aircraft / drone, and now you have converted a relatively simple air launch concept into one that requires TWO stages before the rocket even is dropped (the aircraft pulling, then the carrier)And scaling this up would be difficult - but that is a problem shared with all air launch concepts.Gliders are a lot easier to scale, and a lot cheaper than traditional aircraft. The pulling aircraft can more likely be something that can fly in other revenue service arrangements than a dedicated air launcher. It is somewhat rube golberg, but that's not always bad.~Jon
I don't see the real benefit of this. You still need to make a custom carrier aircraft / drone, and now you have converted a relatively simple air launch concept into one that requires TWO stages before the rocket even is dropped (the aircraft pulling, then the carrier)And scaling this up would be difficult - but that is a problem shared with all air launch concepts.
Quote from: Rocket Science on 02/03/2015 11:43 pmWhy not place two turbofans over each fusalage and make do without the tow? But that's just me...Oh yeah, no worries, just add a full-blown propulsion system. No biggie. :-)~Jon
I don't know if a rocket propelled carrier can be classified as just a "glider". There is certainly propulsion involved, even if it doesn't activate until after the glider is disconnected.
People normally freak out about my "gamma maneuver" concept of lighting the launch vehicle's engines prior to staging, but part of the point of a glider is that it's an unmanned, relatively low cost vehicle that you can take higher (perceived) risks with.
Quote from: jongoff on 02/04/2015 03:36 amPeople normally freak out about my "gamma maneuver" concept of lighting the launch vehicle's engines prior to staging, but part of the point of a glider is that it's an unmanned, relatively low cost vehicle that you can take higher (perceived) risks with.When I thought about how you'd do an intact abort on a TSTO some kind of test firing (even at partial thrust) seemed the only sensible way to test the system. If the engines fail to light while still attached to the glider then (in principal) you get the payload back intact and the customer lives to launch another day.I think customers like this idea.
Quote from: john smith 19 on 02/04/2015 04:20 pmQuote from: jongoff on 02/04/2015 03:36 amPeople normally freak out about my "gamma maneuver" concept of lighting the launch vehicle's engines prior to staging, but part of the point of a glider is that it's an unmanned, relatively low cost vehicle that you can take higher (perceived) risks with.When I thought about how you'd do an intact abort on a TSTO some kind of test firing (even at partial thrust) seemed the only sensible way to test the system. If the engines fail to light while still attached to the glider then (in principal) you get the payload back intact and the customer lives to launch another day.I think customers like this idea. Yeah, but the carrier plane operators hate the idea. I tried putting together a DARPA ALASA proposal on this topic, but nobody wanted to do that with a manned carrier aircraft. In the end, we didn't have time to propose to both ALASA and DARPA Phoenix, so we ended up dropping the ALASA proposal.
I have to admit, the extreme barrel roll at 1:25 made me burst out laughing
Quote from: jongoff on 02/04/2015 08:19 pmQuote from: john smith 19 on 02/04/2015 04:20 pmQuote from: jongoff on 02/04/2015 03:36 amPeople normally freak out about my "gamma maneuver" concept of lighting the launch vehicle's engines prior to staging, but part of the point of a glider is that it's an unmanned, relatively low cost vehicle that you can take higher (perceived) risks with.When I thought about how you'd do an intact abort on a TSTO some kind of test firing (even at partial thrust) seemed the only sensible way to test the system. If the engines fail to light while still attached to the glider then (in principal) you get the payload back intact and the customer lives to launch another day.I think customers like this idea. Yeah, but the carrier plane operators hate the idea. I tried putting together a DARPA ALASA proposal on this topic, but nobody wanted to do that with a manned carrier aircraft. In the end, we didn't have time to propose to both ALASA and DARPA Phoenix, so we ended up dropping the ALASA proposal.TBH "I" don't think it's such a bad idea and if "I" operated a carrier AC I'd have no problems with it (Which is probably WHY.... )But I think the 'main' issue is probably airframe strain. Great if you design and build for it from the start, not so "hot" if you're planning on using an existing airframe which for the most part ALASA was doing among others. (And besides ALASA seemed to be hung up on top-mounted launch)Looking at the pics of the prototype I don't see it having the structure to allow a powered gamma manuever either...
Quote from: Rocket Science on 02/03/2015 11:43 pmWhy not place two turbofans over each fusalage and make do without the tow? But that's just me...Oh yeah, no worries, just add a full-blown propulsion system. No biggie. :-)
I had some thoughts on how to solve that problem. I may be wrong, but I think you can solve it without actually increasing the loads seen on the aircraft of the aircraft-to-launch vehicle pylon, so long as the aircraft itself is capable of doing the pitchup maneuver without a payload attached.