SSTO's in 0.24

[LethalDose]

Well, no doubt FAR makes it easier.

Truth, but the alternative is using the stock aerodynamic model, which is... well, if you can't say something nice...

Still, your spaceplane will cost quite a lot - these arerospace parts are among most expensive (and you will lose fraction of that each launch even if recover it). So its not necessary will be more cost effective than just do a small two-stage rocket launch for comparable weight.

Oh, I agree that the parts should be expensive. Like, really expensive. IMO, it should be a major investment to build the SSTO, and that cost should need to be amortized over multiple missions. I doubt the devs will go that far, though.

And again, as myself and other posters pointed out, it's possible to simply refuel and not recover the vessel, therefore not losing any money beyond the initial cost.

Spaceplanes were never really efficient in mass fraction, since they have to haul all of these airbreathing parts and wings in space (where they just dead weight).

Those parts you're describing as "dead weight" are the parts that are actually doing most of the work, at least in my SSTOs. I'm typically hitting 1500 m/s before switching to closed mode on my RAPIERs (not sure if that's orbtial or surface tho). I only need a few hundred more dV to get into orbit. That's what makes the SSTO so efficient: those parts are working where they're not dead weight.

As far as mass fraction goes, in the SSTO I mentioned above the weight of the resources delivered is ~ 5.5 t.

5.5t payload / 23t full plane = 23.9% payload fraction to LKO.

Personally, I don't think that's too shabby, especially since I could make it substantially higher if I got rid of the 3 mk1 Lander cans (their MP is stored for return and not delivered to the station) or included the mass the of life support resources I'm hauling, too.

The issue with SSTO payload fractions is that they scale horribly. As the SSTO get bigger, they payload fraction tends to drop and they're way harder to engineer. I've tried, but I've never been happy with the results. Mods like SP+ or B9 might make it better, but I'm trying to do as much as I can with the stock game and mods that either increase challenge (like TAC-LS & DRE) or solve some the games more glaring issues (VOID & FAR). Like I said above, moderate or larger payloads or structural payloads are better handled with traditional expendable launch systems (basically, staged rockets).

Anyway, we will have to wait and see what exact cost values, recover fractions, etc 0.24 will have after release. Probably they will strike some semi-balance for stock, but mods like FAR could skew it quite a lot.

Yep, basically. FAR will still be worth it for me, though. I think there's always going to be a back and forth between using reusable SSTOs and Progress-style expendable vessels for orbital replenishment.

Edited July 1, 2014 by LethalDose

[firestorm126]

My plan is going to be to add probes onto my first stage, then release it with some fuel left and use the probe to land it (providing there is a reason to reuse parts which i'm assuming there will be). Then any other stages will just be light and cheap.

[LethalDose]

I think this patch calls for the addition of letting "on-rails" parts actually land, if the vessel passes some sort of "deployed parachutes onboard in sufficient amounts". This would allow more staged rockets to be economical, as you could attach chutes and save them, even though physics might not be loaded for that staged part. Arguably it all depends on the recovery amounts, and the balance of the economics, but if this whole system shouldn't be completely trivial, then SSTO's as it right now, will be the "go to" lifters, even if it does require more launches. To strike a balance will be hard, but I think staged rockets should be allowed to at least in some capacity, save their staged parts if effort to do so is put in by the player.

Eh, for what it's worth, I think assuming that SSTOs will be the "go to lifters" for everything is vastly overstating the issue, if for no other reason than engineering SSTO spaceplanes to lift huge payloads is a headache. ANd I don't see a difference between spamming 'chutes on an SSTO rocket and spamming 'chutes on multiple rocket stages, like would be done if they let "on-rails" parts land.

[Alshain]

They just need to replace auto delete with auto recover for any object with adequate parachutes deployed or adequate fuel and TWR to land itself.

If I recall, that's what the mission control mod does.

That would work. There is more than one solution for sure. Just that in order for it to work there has to be a solution.

[Raven.]

In the stock game, I doubt that SSTO space planes would dominate. Now in a modded install, with KAS and mods such as B9 that offer much better space plane parts, I think it'll be a much different story. Especially with KAS, since refueling ops on the ground would be made considerably easier.

[Jouni]

They can also use efficient air-breathing engines that can be almost 10 times as efficient than rockets by reaction mass (they have ISPs 3 - 5 times greater than rockets and don't require Ox, which is more than half of the reaction mass required for rockets) for more than half their flight. These properties of spaceplane SSTOs can actually allow them to be lighter than comparable rockets.

KSP jet engines are actually more like 100x more fuel efficient than rocket engines. The game counts intake air as reaction mass, and as a result, air-breathing engines burn 15-16x less fuel than they should.

[KerbMav]

Well, the cost of the fuel truck is probably less than the cost of the space plane, so it's still a gain. And you can refuel the trucks by just spawning a fuel tank with a docking port on it.

I would not even refrain from refueling the tanker via a savegame edit - or creating a big fuel tank containing millions of fuel, spawning and moving it empty and filling it up.

[LexDavis]

I love all these responses. It's getting me all giddy . I think before SSTO's become really useful they'll need some cargo bays, and the spaceplanes need to be redone completely, aerodynamic model and all. I really hope that .25 focuses on the aerodynamic fixes...

[Alshain]

I would not even refrain from refueling the tanker via a savegame edit - or creating a big fuel tank containing millions of fuel, spawning and moving it empty and filling it up.

Or just use Kethane and atmospheric crafts to set up a mining operation on Kerbin.

[Corw]

I love all these responses. It's getting me all giddy . I think before SSTO's become really useful they'll need some cargo bays, and the spaceplanes need to be redone completely, aerodynamic model and all. I really hope that .25 focuses on the aerodynamic fixes...

SSTO can be really useful on its own. Think about it and expand the re-usability a bit. If you build a reusable vehicle for travelling from Kerbin orbit to moons and back to orbit, you can move reports from orbit to ground with SSTO. So you never recover the service module and lander, you keep reusing them and you reuse SSTO to move crew and science. After you have set up that, al you actually need to spend/launch to orbit is fuel and that cuts the weight a lot.

Or just use Kethane and atmospheric crafts to set up a mining operation on Kerbin.

If you add source of fuel out of the designed system, you have basically threw stock balance trough the window. You could have just as well edited the saves to refuel, the effect would have been the same.

[RidingTheFlow]

SSTO can be really useful on its own. Think about it and expand the re-usability a bit. If you build a reusable vehicle for travelling from Kerbin orbit to moons and back to orbit, you can move reports from orbit to ground with SSTO. So you never recover the service module and lander, you keep reusing them and you reuse SSTO to move crew and science. After you have set up that, al you actually need to spend/launch to orbit is fuel and that cuts the weight a lot.

Well thats where it get wierd, because to recover reports you will have to recover vessel. And whole SSTO ship is more expensive to recover (you lose more money as fraction of cost) than just capsule with chute.

[Sky_walker]

That's not everything: he also assumes that capsule will be more expensive than fuel his SSTO needs - which might not be the case.

[RidingTheFlow]

That's not everything: he also assumes that capsule will be more expensive than fuel his SSTO needs - which might not be the case.

Well, that what I include into "more expensive to recover" definition. Because we will get a fraction of original part cost (unclear yet, how much), and spent fuel obviously won't recuperate any cost (and consider that Harvester already said that majority of fuel tank cost will actually be fuel - so empty fuel tank will hardly get you anything back).

[Seshins]

i would love crew transfer contracts between the KSC and a station or some such. Would give me at least a real reason to build and develop space planes. I've dabbled...but never been very successful.

[LexDavis]

I've dabbled...but never been very successful.

you should get spaceplane plus. it adds great wings and has a good mk2 system.

[No one]

Well thats where it get wierd, because to recover reports you will have to recover vessel. And whole SSTO ship is more expensive to recover (you lose more money as fraction of cost) than just capsule with chute.

Or you could just have a Kerbal take all the reports and then recover the Kerbal.

In the current version I generally do that anyway because it's much safer to land a command chair+kerbal+ion thruster than a larger ship with science equipment. Also, since I'm not returning the heavy ship+science equipment to Kerbin, only a tiny ion thruster+command seat+xenon, it takes practically no mass to return.

[RidingTheFlow]

Or you could just have a Kerbal take all the reports and then recover the Kerbal.

How do you refuel the plane? It will sit on the runway without fuel.

(yes I know you can use mods, but mods can "solve" anything - and its impossible to get a clear definition of what "0.24" is if we including all possible mods).

[No one]

As other people have said, you create a fuel tank on wheels, dock, refuel.

[RidingTheFlow]

As other people have said, you create a fuel tank on wheels, dock, refuel.

It could not be as easy as you think. Trying to dock things on wheels is a bit of a pain, since hard to make alignment perfect. I had so much trouble trying assemble bases on ground this way.

To be fair, I think stock KSP should have "refuel" button in addition to "collect" button, and "refuel" should become available when you have craft sitting either on runway or pad.

Edited July 2, 2014 by RidingTheFlow

[LexDavis]

im about to try....wish me luck

[LexDavis]

To be fair, I think stock KSP should have "refuel" button in addition to "collect" button, and "refuel" should become available when you have craft sitting either on runway or pad.

that's an awesome idea

[No one]

It could not be as easy as you think. Trying to dock things on wheels is a bit of a pain, since hard to make alignment perfect. I had so much trouble trying assemble bases on ground this way.

The claw would also work.

[RidingTheFlow]

The claw would also work.

D'oh! Silly me, keep forgetting about power of klaw

Yep, it works - just built a refuelling truck which docks using claw pretty well. Though initial setup is a bit of a pain, since you can't just spawn it on the runway along with plane (KSP doesn't want to) - have to keep going to nearest taxiway, which adds time to refuelling process.

Edited July 2, 2014 by RidingTheFlow

[LexDavis]

on my way to space, then hopefully coming back to refuel...testing for .24 has begun

[No one]

D'oh! Silly me, keep forgetting about power of klaw

Yep, it works - just built a refuelling truck which docks using claw pretty well. Though initial setup is a bit of a pain, since you can't just spawn it on the runway along with plane (KSP doesn't want to) - have to keep going to nearest taxiway, which adds time to refuelling process.

The klaw is amazing. I really need to learn to dock without it, but it works fine for all my purposes.

I haven't used planes, I'm waiting for them to fix aerodynamics before doing so. Can you land the plane, taxi it a tiny bit off the runway, then not have very far to go with the refueling truck? Or do planes not taxi well on grass?