sevenperforce

Design Challenge: Orbital Shuttle

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Posted (edited)

Challenge: Design and model a fully-reusable PSTO (parallel stage to orbit) shuttle, suitable for taking a crew to orbit and returning them safely to Earth.

People get excited about SSTOs (both of the VTVL and winged varieties), but for Earth, using multiple stages is almost always more cost-effective. However, we've never once flown a fully-reusable human-rated shuttle, and there's no obvious configuration for a fully-reusable shuttle that uses staging.

In particular, I like the idea of a parallel-stage-to-orbit design, where all the launch engines fire on the pad together, with the orbiter engines continuing to fire through stage separation (think Space Shuttle). This introduces additional complications, particularly with respect to configuration.

Some considerations:

  • 0/0 LAS. Being able to escape in the event of a booster RUD is ridiculously important, from pad to separation. The orbiter either needs to have sufficient thrust to push itself free of an exploding booster, or it needs auxiliary solids for LAS, or it needs full cabin ejection with chute recovery.
  • COM/COTCenters of mass and thrust in a vertically-stacked launch vehicle are simple, but for a parallel-staged launch vehicle, it's a little more difficult. The SSMEs had ridiculously high gimbal ranges to help with this, but with a fully-reusable launch stack things may be more or less complicated.
  • Engines and crossfeed. Using the same engines and fuel on the orbiter and the booster simplifies operations and can also allow for fuel crossfeed, but that does introduce some additional complications. If the launch engines are used for orbiter LAS, then they will be large enough to take full advantage of propellant crossfeed.
  • Booster recovery. A liquid fly-back booster is one option; a RTLS tail-sitting booster with landing legs a la Falcon 9 is probably better. No splashdowns for this. Asymmetric thrust and COM may be a consideration depending on how the launch configuration looks.
  • Orbiter recovery. Again, no splashdowns. The orbiter can have wings and landing gear, or it can come back and land vertically with landing legs. However, if it is going to land on its tail, then the crew cabin probably needs to be ejectable using landing-abort solids and chutes, since a tail-first vertical landing is a high-risk maneuver. The ideal solution is to have landing engines which (somehow) can vector or change orientation to allow a vertical landing in horizontal attitude, like sci-fi spaceships. This allows minimal-risk landing and immediate egress.
  • Lifeboat. If the cabin is ejectable, then it makes sense to allow it to act as an orbital lifeboat in the case of orbiter damage a la Columbia. However, this means it either needs its own RCS and TPS. It may be possible to integrate its RCS and TPS for use within the orbiter.
  • Airbreathing. Should you use a rocket-combined-cycle airbreathing engine on either stage? It's a good question. On the one hand, having airbreathing engines on the booster reduces the weight penalty (since they don't have to go to orbit) and can assist in recovery. Having an airbreathing engine on the orbiter increases weight penalty, but could be helpful for landing since airbreathing engines are more readily vectorable than rocket engines, which must be gimballed. It's also possible to conceive a partial airbreathing engine, like an air augmentation shroud on the booster which wraps around the orbiter's launch engine.
  • Altitude compensation. If the orbiter engine doesn't have altitude compensation, it will incur a specific impulse penalty. However, aerospike engines are heavy. An SSME pressure-compensated engine is one possibility. Another possibility is to have the orbiter engine interface with the booster body in such a way as to allow a higher expansion ratio after separation. Keep in mind, however, that you may be using the launch engine for recovery as well.
  • Cargo. A cargo bay is not necessarily a requirement, but it definitely adds versatility. A cargo bay can also be used to add an auxiliary fuel tank for extended on-orbit operations or BLEO missions. Consider orbital refueling as well.

I have a few ideas for how to pull this off, but I'm really interested to see the kinds of things the forum can come up with. There are a lot of options here, and none of them are automatically ideal.

Design, describe, and model your submission! You don't necessarily have to fly it; it will probably be ridiculously overpowered for stock KSP. Excited to see what everyone comes up with.

Edited by sevenperforce
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Posted (edited)

Looks interesting. What are the rules regarding mods? I'd assume nothing cheaty is allowed, but what about stock-balanced part mods?

Edited by eloquentJane

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43 minutes ago, eloquentJane said:

Looks interesting. What are the rules regarding mods? I'd assume nothing cheaty is allowed, but what about stock-balanced part mods?

Any mods you like. I'm really mostly interested in seeing creative launch configurations people come up with, particularly ones possible for the real world.

If there's interest in scoring and a leaderboard later on, I can put that together.

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Orbiter recovery. Again, no splashdowns. The orbiter can have wings and landing gear, or it can come back and land vertically with landing legs. However, if it is going to land on its tail, then the crew cabin probably needs to be ejectable using landing-abort solids and chutes, since a tail-first vertical landing is a high-risk maneuver. The ideal solution is to have landing engines which (somehow) can vector or change orientation to allow a vertical landing in horizontal attitude, like sci-fi spaceships. This allows minimal-risk landing and immediate egress.

So like slow down inside the atmosphere and convert horizontal flight into a vertical landing, like a Harrier Jet? VTOL style?

 

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26 minutes ago, Andetch said:

Orbiter recovery. The orbiter can have wings and landing gear, or it can come back and land vertically with landing legs. However, if it is going to land on its tail, then the crew cabin probably needs to be ejectable using landing-abort solids and chutes, since a tail-first vertical landing is a high-risk maneuver. The ideal solution is to have landing engines which (somehow) can vector or change orientation to allow a vertical landing in horizontal attitude, like sci-fi spaceships. This allows minimal-risk landing and immediate egress.

So like slow down inside the atmosphere and convert horizontal flight into a vertical landing, like a Harrier Jet? VTOL style?

Yeah, basically. At the risk of succumbing to rule of cool, this really is a lot better than the alternatives. You eliminate the dead weight of landing gear and you have no risk of tip-over. Egress is feasible as well (something that seems ridiculously difficult for a proposal like ITS).

I see three ways of doing this. The first is to have fully rotating engine nacelles like a V22 Osprey or Firefly's ship Serenity. Drawback here is additional dry mass for the rotation mechanism, as well as moving parts that can fail.

Another approach is to use an airbreathing engine (turbojet or turborocket) for launch assist and for landing, since turbine exhaust can be easily vectored to 90 degrees or more (think F35B) and rocket exhaust cannot. The drawback here is increased dry mass to orbit; it would be better to use the turbines on the booster than to carry them into orbit every time.

The final, and perhaps most interesting approach, is to have altitude-compensated OMS engines for orbital insertion/maneuvering which are aligned perpendicular to the launch thrust axis. These engines wouldn't fire during launch, but once out of the atmosphere, they could circularize or change orbit without aerodynamic drag. During landing, they would be able to lower the orbiter straight down to the tarmac.

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So a bit unsure of whether we're talking vert or horizontal launch here, and I made a design. It did fail miserably, however, the escape device worked great up to the point that the game locked my controls out due to taking screen shots and I got to watch them fall back and impact without deploying the chutes before restarting my pc. Some of the pictures are pretty though.... Not that imigur is letting me upload them, bastads.

 

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6 minutes ago, Andetch said:

So a bit unsure of whether we're talking vert or horizontal launch here, and I made a design. It did fail miserably, however, the escape device worked great up to the point that the game locked my controls out due to taking screen shots and I got to watch them fall back and impact without deploying the chutes before restarting my pc. Some of the pictures are pretty though.... Not that imigur is letting me upload them, bastads.

Look forward to seeing the pics!

Vertical or horizontal launch are both fine; the goal is something that would work IRL, though.

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Eva ship transfers work just fine IRL, right? Hehe...

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9 minutes ago, Andetch said:

Eva ship transfers work just fine IRL, right? Hehe...

We laugh, but there's a slim chance that EVA ship transfer could have saved the crew of Columbia if they'd noticed the body damage before re-entry.

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2 minutes ago, sevenperforce said:

We laugh, but there's a slim chance that EVA ship transfer could have saved the crew of Columbia if they'd noticed the body damage before re-entry.

Not enought eva suits onboard

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10 minutes ago, rkarmark said:

Not enought eva suits onboard

Yeah, it would have been tough. Atlantis was already gearing up for another mission, so it was available. It would have needed to be pushed through to launch, skipping 90% of preflight checks, and launch and rendezvous. Then they would have had to actively hold the two ships in a bay-to-bay perpendicular orientation (since neither had a Canadarm for grappling) while they did repeated EVA from Atlantis to Columbia and back, one crew member at a time. Doable, but just barely.

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Yeah.... Really they need to get the tech to do a skydive from space..

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Quick question: would I be able to land the boosters on parachutes? 

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10 minutes ago, Andetch said:

Yeah.... Really they need to get the tech to do a skydive from space..

Skydive from space is easy enough. Skydive from orbit, not so much. There have been proposals, but I would not want to be the test subject.

6 minutes ago, 53miner53 said:

Quick question: would I be able to land the boosters on parachutes? 

You can use chutes for convenience in KSP so you don't have to manually fly the boosters back, but the configuration should be such that they could conceivably be landed either on the runway (with landing gear) or propulsively (with landing legs, like a Falcon 9 or New Glenn first stage).

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Posted (edited)

So with putting chutes on boosters that auto deploy etc, how does one get over the fact that if they move more than 20km from the controlled vessel in the atmosphere the game just removes them.... This is the issue I had.....  lifter stage detachs at 30km high, vessel will get more than 20 kms away with both inside atmosphere, so game removes one. Unless there is a mod to stop this?

Edited by Andetch
correction

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5 minutes ago, Andetch said:

So with putting chutes on boosters that auto deploy etc, how does one get over the fact that if they move more than 20km from the controlled vessel in the atmosphere the game just removes them.... This is the issue I had.....  lifter stage detachs at 30km high, vessel will get more than 20 kms away with both inside atmosphere, so game removes one. Unless there is a mod to stop this?

The Stage Recovery mod can recover them automatically. It can also land liquid stages propulsively if they have a probe core and enough fuel remaining.

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16 minutes ago, Andetch said:

So with putting chutes on boosters that auto deploy etc, how does one get over the fact that if they move more than 20km from the controlled vessel in the atmosphere the game just removes them.... This is the issue I had.....  lifter stage detachs at 30km high, vessel will get more than 20 kms away with both inside atmosphere, so game removes one. Unless there is a mod to stop this?

I'd be interested to see your design even if you aren't able to successfully fly it yet.

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Posted (edited)

Meh, I am a purist so is a thing I will never achieve.... As for the original designs I lost them, but could put it into my current go to tourist ship, I put a small cargo bay with a simple core and aerial inside on the top of the stack of boosters all strutted together...  think one kickback housing the core at the centre, and then loads more attached radially and strutted together nice and tight! Rest of the ship sits on top, which incidentally is a ship I have dubbed The Holy Grail, due to it's ability to go to minimus, land, refuel in minimus orbit, and then either go to the mun, land and go to kerbin, with a good recovery value landing far from ksc (I play unmodded so rarely get a ksc landing right), OR it can go to Duna instead, refuel at Ike, land on Duna, take off, refuel, go back to Kerbin. If I could land the kickbacks, and reliably land at ksc by hand it would be sweet, as then the only costs are fuel! There are a few variants I made with science, auto pilot, lab etc. 

I have a picture of the ship meeting the refueling rig around Ike, I took the picture because I liked it and I share it here for you to look at, and will dig out the designs and post the ship file.

The one on the left is the same thing that leaves kerbin, minus the kickbacks...

FcOphjI.png

Edited by Andetch

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What's the configuration like? Does it take off vertically or horizontally? How about landing? How many boosters, and how are they arranged? What is the LAS setup?

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Here's one relatively simple way to achieve a PSTO system.

Start with a Shuttle-shaped delta-winged orbiter and put a suitable number of Raptors under it; replace the cargo bay with an internal methalox tank. Strap a pair of Raptor-powered methalox boosters on either side, over the wings, with crossfeed to the internal methalox tank.

The boosters separate and RTLS to land on landing legs; the orbiter continues to orbit and then returns for a gliding landing like an X-37B or the Shuttle.

LAS is an issue, though with a high enough T/W ratio on the orbiter, it can just push itself clear of a booster RUD and fly back to the landing site under power.

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So no idea whether this is relevant, but this is a quick reconfigure I did of my Holy Grail to incorporate recovery of the lifter stage. You will want to throttle down the kickbacks in the shipfile to get the grav turn correct. I got a lot closer to my original ideas this time, but lost the lift stage because the re entry was far too steep! I hope you enjoy the concept.

Anyway I gotta go! Laters!

https://drive.google.com/open?id=0BxP5XMEnEjPiYmN5eXVhY0J3SkE

Tabutzv.png5qlKyoy.pngy2ufCOt.pngcdKw84g.pngr4fwdcz.png

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My attempt is incoming soon! I'm going to try to make it a long range one.

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I designed a system that works quite well, with the orbiter's CRG-100 cargo bay replaced by a Mk 3 LFO tank long.  The 'stack' takes off vertically with the booster half feeding all the engines until it's empty, whereupon it separates and glides to landing.  The orbiter does its thing and lands like the space shuttle.  The only difference between the two is  the cargo bay and internals and slightly different wing placement.

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After searching for a bit through Google Images for inspiration for this challenge, I've encountered (amongst other things) a shuttle which is basically a spaceplane with drop tanks strapped above the wings, several lifting body designs, and something which very much resembles an Imperial star destroyer. I've also found another design which will probably provide quite a large proportion of the inspiration for my entry to this challenge, assuming I can get it to work.

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15 hours ago, Andetch said:

So no idea whether this is relevant, but this is a quick reconfigure I did of my Holy Grail to incorporate recovery of the lifter stage. You will want to throttle down the kickbacks in the shipfile to get the grav turn correct. I got a lot closer to my original ideas this time, but lost the lift stage because the re entry was far too steep! I hope you enjoy the concept.

Anyway I gotta go! Laters!

Looks great! Using radially-mounted engines to keep the orbital stage's engines clear of the booster is quite kerbal.

15 hours ago, Thor Wotansen said:

I designed a system that works quite well, with the orbiter's CRG-100 cargo bay replaced by a Mk 3 LFO tank long.  The 'stack' takes off vertically with the booster half feeding all the engines until it's empty, whereupon it separates and glides to landing.  The orbiter does its thing and lands like the space shuttle.  The only difference between the two is  the cargo bay and internals and slightly different wing placement.

Got photos?

10 hours ago, eloquentJane said:

After searching for a bit through Google Images for inspiration for this challenge, I've encountered (amongst other things) a shuttle which is basically a spaceplane with drop tanks strapped above the wings, several lifting body designs, and something which very much resembles an Imperial star destroyer. I've also found another design which will probably provide quite a large proportion of the inspiration for my entry to this challenge, assuming I can get it to work.

Are the drop tanks recoverable?

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