Aeroplanes to lift rockets

[Lopez de la Osa]

Is viable to use aeroplanes to lift about 20.000 meters, or so, a rocket and then launch a rocket from there to orbit? I suppouse it is able, but I want know if it is viable.

I mean, 'able' is something that can be done. 'Viable' is something that can be done and is a good idea.

I am thinking that when you launch the rocket you have to manage two independents crafts, at least if you want to recover the aeroplane... and I want to do so. And that task must be a very dificult task in an atmospheric enviroment, isn't it?

[pincushionman]

Possible, yes, but very hard. There are mods that can help, though, like MechJeb to circularize your rocket while you fly the plane, or one that is essentially a time-control mod to let you fly one craft, then rewind time and deal with the other.

The other option is to loft your rocket so high you can go hell-for-leather and land before you need to begin your circularization burn. This is no easy task.

[RizzoTheRat]

Real world yes, see Spaceship 1, Pegasus, or ASM-135

In KSP it's a bit trickier because you can't control both craft.  There is a mod, but I can't remember what it's called, that allows you to save at the point of separation, land the launch vehicle and recover it's costs, then go back to the save and fly the orbiter the rest of the way.

 

Edited May 4, 2016 by RizzoTheRat

[Stoney3K]

That mod is called "Flight Manager for Reusable Stages". Not sure if it is updated for 1.1.2 though.

In defense of stock, SAS will now keep a plane flying happily through an atmosphere even if you're not controlling it, and switching vessels in atmosphere is now possible.

[mk1980]

in case you didn't know: in KSP, single stage to orbit planes (or rockets) are quite possible. i guess that's a pretty good alternative to using a plane to carry a small rocket into the stratosphere.

so even if you can't use the plane + rocket combination, you can get similar results by using a plane that flys to orbit, drops off the cargo satellite or probe or whatever and returns to the space center.

[Zhetaan]

I know that in pre-1.0, it was uncommon-but-not-surprising to see jet-based first stages.  However, the cost of jet engines compared to LFO rockets--let alone SRBs--made it fairly expensive in career.  I don't know whether it's possible in post-1.0 to do it; jets took a blow to performance.  Additionally, the jets were oriented vertically, and you are asking about launching from an aeroplane.

I've seen a few YouTube videos of people who launched their rockets from jet-based launchers.  The challenge comes from KSP's internal mechanics:  if you pilot the rocket, your jet may crash before you circularise, but if you pilot the jet, instead, you may not be able to land it before your rocket coasts to reentry.  And if you pilot either one, the game may delete the other if it drifts too far away in atmosphere!  Assuming that the wiki Recovering Spent Stages is still correct, you'll need to get a lot higher than 20,000 metres.

Here's an example of a powered recovery (rockets, though, not planes--but it gives you an idea of the challenge): @Raptor9 made a great video of flying a Recoverable Booster.

Also, per the usual refrain, there's a mod for that:  feel free to try @SIT89's FMRS.  It was last updated officially for 1.1.0, but the thread says it works in 1.1.2.

As far as viability, the endpoint of this line of design thinking is that you get a vehicle whose only recurring cost is the fuel it uses.  We already have that endpoint: you're applying the same principle that guides the development of an SSTO.  You aren't quite to single-stage, of course:  this is still in 'recoverable booster' or 'First-Stage-to-' territory.  Even stretching the definition and calling your booster an FST-not-quite-O or maybe an FST-almost-O still means you have parasitic engine mass in the rocket payload when compared to a full SSTO (which, for this comparison, has no rocket payload).

On the other hand, the expenditure of engine mass is academic if the engine is recovered.  The only true cost with a 100% recoverable spacecraft--and concordantly, the only viable standard for viability when considering such craft--is fuel expenditure.  Because that rocket payload's engine is parasitic mass, you're using more fuel in the booster to lift it, even if it is only liquid fuel and not LFO.  Will an aerolauncher use less fuel than a staged rocket?  Absolutely--even if you ignore lower stage destruction and don't include (parasitic) recovery engines or parachutes.  Will it use less than a rocket SSTO?  Maybe--I'm not sure how the cost interplay between extra engines versus extra oxidiser works out.  Will it use less than a jet SSTO?  Absolutely not.

[Foxster]

It's quite do-able for small craft. Not so great for anything large. 

Using a jet engine(s) for a first stage on a rocket launched vertically and then discarded as junk is a good way to loft a smallish craft and keep the weight down. 

[N_Molson]

Well, it works quite well, but as said above, the issue is that the carrier-plane goes on a suicide mission. Which ruins a bit the idea of cutting the costs.

In real life, that solution is viable only for light payloads, as carrying something like a Proton or Atlas-V rocket under an airplane defies any sanity.