TSTO Spaceplane with forward drop tank?

[FlyingPete]

I remember a fairly old design posted on here (which I now can't find) for a vertically-launched spaceplane/shuttle with an external tank. The difference was the drop tank was mounted on the nose of the orbiter, rather than to the side or behind- the latter two either suffer from offset thrust or are hard to make stable due to the wings up front. The idea being that the orbiter's wings are usefully acting as stabilisers/control surfaces during the atmospheric phase. When the drop tank's fuel is exhausted, it is jettisoned clear of the orbiter which continues on its internal fuel (with the same engines.) I guess the suborbital tank could be parachuted down for a non-explosive landing/recovery. I don't really bother with spaceplanes usually, but I liked the concept.

Anyone had success with this type of spacecraft in recent versions?

[Van Disaster]

The answer to side tanks/boosters is just to use a pair, you can even stick them on the wingtips to keep them aligned with CoM. For rear booster stages, just stick wings on those too - no reason you can't have tandem wings.

[insert_name]

@Cydonian Monk had one that worked pretty well, forgot what it was called

[Fellow314]

I did these a while ago, but the tanks are mainly on the side.

 

[Cydonian Monk]

I called mine Titanium. It needed some offset-tool/clipping to get the decoupler centered up, but it definitely works.

An older version of it is up on KerbalX:

https://kerbalx.com/CydonianMonk/Titanium

 

Edited September 20, 2017 by Cydonian Monk

[sdj64]

Mine wasn't the first, but it might be the one you're thinking of.  It entered into several missions of the Shuttle Challenge but I decided to do something different for the most recent.  It should still work in the current version of KSP.

https://kerbalx.com/sdj64/Chevalier-Shuttle-H2

[FlyingPete]

7 hours ago, Cydonian Monk said:

I called mine Titanium. It needed some offset-tool/clipping to get the decoupler centered up, but it definitely works.

An older version of it is up on KerbalX:

https://kerbalx.com/CydonianMonk/Titanium

 

Titanium looks good How does it compare economically to using a conventional rocket? If you can make it out of atmo before separation, and circularise before the tank de-spawns from existence, I guess you could switch back to it and follow it down for parachute recovery hence 100% recoverability. That does require a fairly precise ascent profile though.

[Cydonian Monk]

7 hours ago, FlyingPete said:

Titanium looks good

Thanks. 

7 hours ago, FlyingPete said:

How does it compare economically to using a conventional rocket? If you can make it out of atmo before separation, and circularise before the tank de-spawns from existence, I guess you could switch back to it and follow it down for parachute recovery hence 100% recoverability. That does require a fairly precise ascent profile though.

I’m not sure about the math for the tank, but this design does recover and reuse all of the engines (there’s only one of them). So even with losing the tank you’re looking at a nice recovery cost vs a conventional non-recoverable rocket. (I’ve toyed around with a larger variant too that also works.)

With reentry heat, the likelihood of the tank surviving in its present design is non-existent. You could probably add a deployable heat shield to one end of it, but holding angle of attack on reentry would require some form of RCS.... I’m sure it could be done, but I’m questioning if the added cost from the fuel needed to carry the extra mass of RCS/heatshield/parachutes to space and back would be less than the cost of discarding the empty tanks.

[FlyingPete]

41 minutes ago, Cydonian Monk said:

Thanks. 

I’m not sure about the math for the tank, but this design does recover and reuse all of the engines (there’s only one of them). So even with losing the tank you’re looking at a nice recovery cost vs a conventional non-recoverable rocket. (I’ve toyed around with a larger variant too that also works.)

With reentry heat, the likelihood of the tank surviving in its present design is non-existent. You could probably add a deployable heat shield to one end of it, but holding angle of attack on reentry would require some form of RCS.... I’m sure it could be done, but I’m questioning if the added cost from the fuel needed to carry the extra mass of RCS/heatshield/parachutes to space and back would be less than the cost of discarding the empty tanks.

You're probably right- after all, you're only throwing away tanks, a decoupler and maybe some sepratrons which is next to nothing. I threw together a TSTO once to test the idea of dropping the airbreathing engines/empty tanks and intakes. In an ideal world these would be remote-controlled for either a parachute landing downrange for recovery. But with them de-spawning it was simply too much to throw away.

[Rune]

Many moons ago, I did a replica of the soviet MAKS spaceplane... an actual serious proposal that even saw some ground test articles built, and some tripropellant engines tested:

 

Rune. I guess having a Mriya built, you just look for stuff to put on it.

Edited September 21, 2017 by Rune

[AeroGav]

On 20/09/2017 at 5:36 PM, FlyingPete said:

I remember a fairly old design posted on here (which I now can't find) for a vertically-launched spaceplane/shuttle with an external tank. The difference was the drop tank was mounted on the nose of the orbiter, rather than to the side or behind- the latter two either suffer from offset thrust or are hard to make stable due to the wings up front. The idea being that the orbiter's wings are usefully acting as stabilisers/control surfaces during the atmospheric phase. When the drop tank's fuel is exhausted, it is jettisoned clear of the orbiter which continues on its internal fuel (with the same engines.) I guess the suborbital tank could be parachuted down for a non-explosive landing/recovery. I don't really bother with spaceplanes usually, but I liked the concept.

Anyone had success with this type of spacecraft in recent versions?

The only problem with a "tank pusher" design is if you want to use the wings to make lift on the way up,  then you'll find it almost impossible to generate any angle of attack as an aircraft that was stable without the tank becomes a lawn dart with the weight of a tank on the front.I vote for a pair of external tanks mounted to the wingtips if a jet-free TSTO is what you're after.   I built something vaguely similar for the Shuttle Challenge (though rather more complex as the challenge was quite demanding)

Spoiler

 

If the design is allowed to use jets, then a spaceplane with nuke engines and droppable whiplashes with intakes and fuel storage under each wing can do an even more convincing job.

Will see if i can rustle up such a thing for you and post back..

[Van Disaster]

A few ideas & demos of lack of aero issues from a couple of versions back - I use FAR, but there's nothing that will make much difference for this sort of mission.

Basic ship on a stick - those little fins are pretty much all that's necessary.

Spoiler

Wingtip boost ( this one was actually HOTOL, so needed even more balancing ); plain tanks would have worked if there was enough grunt but top of aero -> suborbital was a lot more efficient with extra boost engines. If you wanted an actual shuttle replica but a home-made launch system then overwing would seem the place to put the tanks/boosters.

Spoiler

 

Tail-attached vertical launched multistage boost

Spoiler

 

Nose-mounted tanks would seem to lead to all sorts of aero & structural issues if there's any divergence from a perfect launch profile - you won't have the authority for large AoA unless you add small wings to the tank which work as canards - that sounds like a recipe for even more structural issues given you're trying to bend the tank coupling in half, but with a decent attachment point that would probably work quite well.

Edited September 22, 2017 by Van Disaster

[AeroGav]

Well, here's what droppable wingtip jet engines look like .   Sorry this was supposed to be a simple demo craft, but i started getting daft with it.    Surely the most efficient way to launch Skylab is to just bolt wings and engines on the side,  why lug a cargo bay to orbit ?

before they fell off..

A vaguely related TSTO (three stages actually)

 

[Thor Wotansen]

You could also go the PSTO route and give your tank some wings and engines of it's own.  The orbiter gets fuel crossfed from the booster and both bits ultimately glide to a runway landing.

In this example the orbiter is on the left.

[Foxster]

Here's a (stock) thought...

 

Edited September 22, 2017 by Foxster