Skylon v SpaceX: A community challenge

[sevenperforce]

In the age of reuse, space agencies have a decision to make: TSTO rocket or SSTO spaceplane? Of course, until Skylon flies (if it ever does), TSTO rockets are the only game in town. But in Kerbal Space Program, spaceplanes fly with ease...which brings us to this challenge.

Your mission, should you choose to accept it, is to build either an SSTO spaceplane or a TSTO rocket to carry commercial payloads into orbit over Kerbin. Every stage of your launch vehicle must be reusable, and you must use the exact same vehicle to launch each of the following three payloads:

• A 15-tonne survey satellite to polar orbit (150x150 km or higher). The survey sat must be fully functional. (ADDED OPTION: 15-tonne sat constellation in the same orbit)
• A 6-tonne relay comsat to Kerbostationary Transfer Orbit (75x2863.33 km or higher). The relay must be able to self-circularize into an equatorial KSO; the relay must be fully functional.
• A crew vehicle containing at least 7 kerbals to rendezvous with an equatorial space station (200x200 km or higher). The crew vehicle must have independent maneuvering capability and power generation, and must be recoverable. You do not actually have to have an equatorial space station, though if you do, awesome!

The challenge is to build a launch vehicle with the lowest possible dry weight.

Rules:

• General:
  • All entries must use 100% stock parts.
  • No piloting mods, though other mods are fine. Obviously, no infinite fuel or similar cheats.
• TSTO rocket:
  • Both stages must be recovered and must land propulsively. The crew vehicle must have abort capabilities and must also land propulsively (chutes okay for backup; e.g., on abort).
  • Payload fairings, assorted decouplers, and engine shrouds may be jettisoned without recovery.
  • First-stage recovery must be reasonably close to KSC; second stage (and crew capsule) can be recovered wherever you want, as long as it comes down on land.
  • Chemical fuel only (other than on payload).
  • Vertical takeoff from the launch pad.
• SSTO spaceplane:
  • Takeoff and landing must take place on the runway. Must launch and land with probe only; no crew (except for the crew-vehicle launch).
  • No nukes, ions, or solids. Other than RAPIERs, the only rocket engines permitted are low-thrust OMS engines.
  • All payloads must launch and deploy from inside a payload bay.
  • The crew vehicle must be able to dock back inside the payload bay for re-entry. It does not need to have 0/0 abort or independent re-entry.
  • An expendable solid kick stage is permitted for KTO injection of the relay comsat.
  • To reflect that Skylon will need to carry liquid hydrogen for its precooler to work, LF tanks may not be more than 50% full at launch. Oxidizer tanks may be filled completely.

This is a community challenge, so here's how it works. You can submit either a TSTO rocket, an SSTO spaceplane, or both. There will be a leaderboard for lowest-dry-weight rocket and lowest-dry-weight spaceplane, but the overall competition will be between rockets and spaceplanes. The winning leaderboard will have the lowest total mass from the three leading entries.

Good luck!

 

Edited July 19, 2017 by sevenperforce

[Human Person]

Wait, lowest mass wins? The whole point of reusability is reduction of cost, not weight. 

[sevenperforce]

19 minutes ago, Physics Student said:

Wait, lowest mass wins? The whole point of reusability is reduction of cost, not weight. 

True...but if you can manage to make a reusable vehicle, initial cost is not as important as refurbishment cost and operating cost, which scales loosely with vehicle dry weight. In addition, KSP's part costs aren't necessarily very useful; optimizing for dry mass rather than for cost is a much more interesting challenge.

[michal.don]

Interesting idea. Just to make sure I understand correctly - on the spaceplane, we are allowed to take just 1/3 of the plane's LF capacity? Or is that a restriction just on pure LF tanks? (not mixed LF/O tanks)

Thanks,

Michal.don

[sevenperforce]

27 minutes ago, michal.don said:

Interesting idea. Just to make sure I understand correctly - on the spaceplane, we are allowed to take just 1/3 of the plane's LF capacity? Or is that a restriction just on pure LF tanks? (not mixed LF/O tanks)

Thanks,

Michal.don

One third of total liquid fuel capacity. So mixed LF/O tanks can have their oxidizer filled fully but can only have 1/3 of their liquid fuel capacity filled.

If I was being completely fair it would be something like 1/5, given how fluffy liquid hydrogen is compared to kerosene, but I didn't want to make it too ridiculous.

Edited July 18, 2017 by sevenperforce
typo

[Bottle Rocketeer 500]

@sevenperforce I'll try with an SLS-alike Reusable Rocket

Edited July 18, 2017 by Bottle Rocketeer 500

[michal.don]

4 minutes ago, sevenperforce said:

One third of total liquid fuel capacity. So mixed LF/O tanks can half their oxidizer filled fully but can only have 1/3 of their liquid fuel capacity filled.

Thanks for the clarification. It's tougher than it looks like, probably because of the now ridiculous dry/wet mass ratio of the tanks. I'm having serious trouble even getting a dummy payload to orbit, I'm about 400m/s second short.... Damn you liquid hydrogen

[sevenperforce]

5 minutes ago, michal.don said:

Thanks for the clarification. It's tougher than it looks like, probably because of the now ridiculous dry/wet mass ratio of the tanks. I'm having serious trouble even getting a dummy payload to orbit, I'm about 400m/s second short.... Damn you liquid hydrogen

I didn't test this at length; I can change to 1/2 capacity if it will be too difficult to make orbit. I'm sure there are people here with more spaceplane experience than myself.

On the opposite side, the rockets are going to need to reserve hella propellant for propulsive landings, so that's another consideration. Also, piloting a reusable TSTO to orbit requires separation outside of the atmosphere and a lot of careful switching back and forth.

Edited July 18, 2017 by sevenperforce

[Bottle Rocketeer 500]

@sevenperforce Also, does it need to be the same type of rocket or the same actual launcher?

[sevenperforce]

Just now, Bottle Rocketeer 500 said:

@sevenperforce Also, does it need to be the same type of rocket or the same actual launcher?

Same actual launcher; that's the critical element of this challenge.

This concept comes from the idea that making a reusable launch vehicle profitable requires frequent reuse, which means that you can't have a different launch vehicle for each different contract. You need to be able to build and operate a single launch vehicle with enough capacity for the entire range of commercial launches. That's why I have three separate missions to represent the three types of launch contracts available to medium-lift launch providers today: commercial crew, LEO heavy comsat, and GTO medium comsat.

Obviously the payload adapter will vary from launch to launch, but that's expected.

This also shows one of the challenges faced by Skylon: it's not enough to get a single large payload to LEO; you need to be able to put payloads in GTO as well, and you need to be able to launch passengers safely. Skylon must develop a solid kick stage for GTO missions, since the whole launch vehicle cannot make it to GTO. 

[Bottle Rocketeer 500]

@sevenperforce Can I land the first stage at the KSC, second stage elsewhere, and just use a new 2nd stage every launch?

Edited July 18, 2017 by Bottle Rocketeer 500

[sevenperforce]

2 minutes ago, Bottle Rocketeer 500 said:

Can I land the first stage at the KSC, second stage elsewhere, and just use a new 2nd stage every launch?

Sure, I'll relax the KSC landing requirement for the second stage. You can put the second stage down anywhere on land, as long as it lands intact.

Edited July 18, 2017 by sevenperforce

[Bottle Rocketeer 500]

So,I can have a new second stage every launch that is mated to the payload?

[sevenperforce]

10 minutes ago, Bottle Rocketeer 500 said:

So,I can have a new second stage every launch that is mated to the payload?

Not quite sure what you're asking. The payload must decouple from the second stage once it reaches its intended orbit and the second stage must be recovered, just like the first stage must be recovered. But of course you can just use the "Recover" function and go back to the VAB and load the old vehicle when you go to the next payload.

For example, I'm going to do a single-stick TSTO with the payload mounted on top of a heat shield on top of the second stage on top of the first stage. I'll launch to an apogee over 70 km, separate, switch to the first stage and do a boostback burn, switch back to the second stage and burn to orbit, then switch back to the first stage and do the entry, descent, and landing. Then I'll go back to the second stage, correct the orbit, decouple the payload, and then deorbit the second stage; going nose-first on the heat shield until the lower atmosphere and then flipping to land on the engine.

[Bottle Rocketeer 500]

I'll have the second stage land near the KSC in the grasslands and be recovered with a jet. Then, I'd add a segment of the payload, second stage, and interstage on top of the first stage, which would be landed at KSC and transported to the Launchpad. Repeat that 2 more times for the other missions. OR... Do all three missions in one launch using a highly capable upper stage.

[sevenperforce]

19 minutes ago, Bottle Rocketeer 500 said:

I'll have the second stage land near the KSC in the grasslands and be recovered with a jet. Then, I'd add a segment of the payload, second stage, and interstage on top of the first stage, which would be landed at KSC and transported to the Launchpad. Repeat that 2 more times for the other missions. OR... Do all three missions in one launch using a highly capable upper stage.

Oh, you certainly don't need to recover the second stage manually or reuse the same actual first stage; you just have to show that you landed it. You can reload from scratch in the VAB for each subsequent mission.

If people are having trouble with the TSTO architecture, you can even save right after stage separation and simply fly the first-stage return by itself, then re-load the second stage and fly it separately.

You do need to do all three launches separately, though; no single-launch approach.

[Bottle Rocketeer 500]

OK

[sevenperforce]

Edited OP to allow constellation launch to polar orbit and revised 50% limit on LF tanks.

[Bottle Rocketeer 500]

@sevenperforce Can the crew vehicle do a parachute-assisted propulsive landing?

[sevenperforce]

11 minutes ago, Bottle Rocketeer 500 said:

@sevenperforce Can the crew vehicle do a parachute-assisted propulsive landing?

Backup chutes for aborts are fine, but propulsive-only landing is preferred.

[Bottle Rocketeer 500]

I'll have parachute assisted propulsive landing because I'm afraid of a spaghetti rocket or running out of fuel. For the crew vehicle

Edited July 19, 2017 by Bottle Rocketeer 500

[Bottle Rocketeer 500]

@sevenperforce I called my rocket the Kraken 1 or Krazy Rocket Assisted Kumbersome Exciting Nincompoop 1.

First stage landed across the ocean from KSC.

Edited July 19, 2017 by Bottle Rocketeer 500

[Bottle Rocketeer 500]

Stages 1&2 already recovered!

[Bottle Rocketeer 500]

Mission Accomplished! Thankfully, I only put three Kerbals in the RV.

[michal.don]

Hello again,

I completed the three missions in a SSTO.I present: the PseudoSkylon

The dry mass in 28,889 tons and it runs on four RAPIERs and one Terrier as an OMS engine.

Here are the missions:

http://imgur.com/a/heEmp

http://imgur.com/a/HAizr

http://imgur.com/a/ZP7Uy

 I'll enjoy being the best entry for a while, until the spaceplane guys come

Michal.don