Benefits and drawbacks of spaceplanes?

[Null_Pointer]

I've noticed that some KSP players create Space Shuttle type spaceplane designs (or even horizontal takeoff SSTOs). Of course, this may be for role playing purposes, but it got me thinking -- what are the benefits of a horizontal takeoff jet-powered space plane versus a vertical takeoff SSTO (which also has jets to reduce fuel consumption, similarly to Scott Manley's reusable space program launch system)?

I haven't had to much experience, and I've only just started using the B9 aerospace pack (which may invalidate what I'm about to say), but it would appear that horizontal takeoff SSTOs don't have as much payload capacity, so if one was to want a SSTO design for lifting large quantities of fuel/cargo, a vertical takeoff SSTO would be best. Is this still the case with B9 aerospace (since the B9 mod adds some pretty high capacity fuel tanks and some pretty large aircraft)? Also, what are the pros and cons of a vertical takeoff SSTO and a horizontal takeoff SSTO?

[Geschosskopf]

I myself don't see any real benefit to making spaceplanes, other than bragging rights, at least when it comes to just getting stuff to and from Kerbin orbit. Anything a spaceplace can do in this regard, a normal rocket can do better, and with a lot less aggravation in making it work.

Now, some folks like to say they have a "green" space program, where everything is reused. Hence they go for spaceplanes rather than dump boosters all over the place. But this has no bearing on the game, it's just personal preference. And as I understand things from my NASA buddies, the "reusable" Space Shuttle program was a mistake anyway. It cost more to create the global infrastructure to support shuttle operations, and to refurbish the orbiter between flights, than it would have to use disposable rockets. Which is why the replacement for the Shuttle isn't a spaceplane but a 1-shot rocket, and why nobody else is planning on building a Shuttle.

That said, spaceplanes are quite useful for exploring planets with atmospheres. You can cover ground much faster, in greater comfort and safety, than you can with a rover, and can fly over terrain obstacles that stop rovers. But in this case, you're using it as an airplane, not a spaceplane, and thus can get it to its destination from a vertical launch. In fact, the thing doesn't need any space capability of its own.

[Blu_C]

There are some advantages that planes have as a launch vehicle.

Probably the most important one is that Jet Engines have a very high fuel efficiency compared to any of the rocket engines and they also have a good TWR. This means that they can lift more mass for less fuel making the whole launch vehicle smaller and more efficient. This lets you get up to around 18k pretty easily (and higher still if you abuse air intakes properly) which you will notice is well above the majority of the atmosphere. It also isn't out of the question that you can get your orbital speed around 1000m/s without too much difficulty and a half way decent space plane. This means that when you switch to rockets you need both less oomph to get into orbit and that the rocket engines will be more efficient as the lower atmosphere means higher ISP (again meaning your craft is more efficient). If we had a better aerodynamic model it would also mean that the lifting of a payload would be aided by the wings, further improving the efficiency of lifting payloads at lower altitudes.

On the landing side the Space Plane is much more flexible when it comes to land. Yes with practice you can get pretty close to a landing target, but a space plane can get closer still. In fact if you arbitrarily decided to shift landing points for some reason (such as noticing something interesting on the way down) a Space Plane is clearly superior as any rocket is going to have serious issues in doing the same. Obviously this only holds for planets with atmosphere though, without atmosphere a space plane is no better (and probably worse) than a traditional lander.

On the down sides, in my experience Space Planes get difficult to fly after a particular size threshold, which means that for very large payloads a more traditional rocket is still probably a better bet. Also because the aerodynamic model is a bit rubbish currently you really don't get the full benefit from a space plane, you pretty much may as well just strap a bunch of jet engine boosters to a traditional rocket to get you up to ~18k before dumping them. This is actually what I have taken to doing recently, and have a very efficient launch vehicle I've designed for satellite sized payloads. It is basically 2 jet engines that lift things up to 18k, then a couple of SRB's (one after the other) kick the satellite into an elliptical orbit where its own weaker engines can get it to where I want it. Depending on how 'reusable' I'm playing I may even attach parachutes to the parts I'm dropping so they can be 'recovered' and 'reused'.

[bsalis]

In my opinion SSTO Spaceplanes are not very practical for lifting payloads to orbit. I think of them more like cars, not trucks.

More accurately they are orbiter/capsules that can get themselves to orbit. They are good for moving Kerbals around efficiently and safely. You can also reliably land them back at KSC (without guidance from a mod, like MechJeb landing autopilot).

Put some legs on the back and you can also land on bodies that have no atmosphere. A docking port will let you refuel them for deep space travel... as I said, they are just like an orbiter when in space.

[Blu_C]

In my opinion SSTO Spaceplanes are not very practical for lifting payloads to orbit. I think of them more like cars, not trucks.

I didn't think of this distinction. Most of my space planes end up ditching their jet engines since there aren't many places in space they are useful outside of Kerbin. But yeah that is my experience. SSTO's are great for a reusable vehicle to refuel and send up again (say, if you were to set up a remote base on Kerbin for some reason), but they aren't very good at all for getting a payload up as they carry a bunch of dead weight with them.

[annallia]

I don't find them overly useless, just less than useful.

The last time I used them it was for my Laythe colony. I used them as a taxi to take kerbals to and from my station in orbit to the surface. This however annoyed me because I would eventually have an imbalance in fuel/oxidizer on my station where it refueled.. As well I could have done the same job with a rocket just not as accurate with my landings. However now that I am using Kethane I may revisit the idea.

As far as reusable rocketry goes.. I actually worked out a system (though I don't use it) where all of my boosters land safely on Kerbal. The reason I don't use it are two fold (aside from having no benefit in the game so far)

1) When it atmo if it gets too far away from the ship I am controlling it sometimes poofs, so no real point.

2) My system isn't bug free yet, by bug I don't mean it will break KSP or something, but it may break my rocket.

[Johnno]

Most points have already been touched on, the main point I'd like to expand on is reusability. Currently there's no real need for reusability, but once costs/career mode comes along it'll change. If I can get 1-3 crew + a small payload (be it satellite, fuel, a minitug) into orbit at the cost of a few small tanks of jetfuel and a T800 tank of rocketfuel I'll swiftly get ahead in budget compared to conventional launches. Now if I land/recover said craft and reuse it I'll have saved all the money that a conventional rocket spent on engines/tanks that just burned up in the atmosphere.

But right now, it takes more time and skill to do spaceplanes/SSTOs, but at least it's something different to fiddle around with if you were to get tired of conventional launches. I've dabbled more and more into spaceplanes lately and find it fun and challenging.

[Brevillance]

I personally see very little benefit, as there is no costs and the aerodynamic models are a bit quirky.

I really just enjoy them for the challenge. Once you boost a 70 ton object into space you can do it to any other 70 ton object, and anything lighter. Most rocket designs can be quickly adapted for lighter or heavier loads, a SSTO would need a lot of work in order to properly hold larger loads. Im sure that space planes will have their own benefit when costs are associated with things, the aero models are better and the physics interact better, but atm it seems they are better for a challenge, having some fun and trying a different way to get a satellite to orbit..plus i think its really fun to land them

[Geschosskopf]

Most points have already been touched on, the main point I'd like to expand on is reusability. Currently there's no real need for reusability, but once costs/career mode comes along it'll change. If I can get 1-3 crew + a small payload (be it satellite, fuel, a minitug) into orbit at the cost of a few small tanks of jetfuel and a T800 tank of rocketfuel I'll swiftly get ahead in budget compared to conventional launches. Now if I land/recover said craft and reuse it I'll have saved all the money that a conventional rocket spent on engines/tanks that just burned up in the atmosphere.

This all sounds good in paper but it doesn't work that way in real life, as was discovered with the Shuttle program. It cost more to refurbish the orbiter after each flight than it would have to build a 1-shot rocket to do the same job. And remember, the original plan was to refurbish the SRBs, too, but that very quickly went by the boards due to cost and safety issues. Basically, the Shuttle was a white elephant, all because it was supposed to save money by being "reusable".

So, the question is, when we have to start buying parts in KSP, will we also have to pay realistic refurb costs? If not, then reusable spaceplanes would have an unrealistic price advantage. If we do have to pay for refurbs, though, then they'd be nothing but toys for the idle rich . There's also the question of how much of your career mode R&D you'll be able to do in a separate sandbox game, then import the craft files. If you can't do that, then you'll have to pay for dozens of failed spaceplanes you'll inevitably have .

[Johnno]

So, the question is, when we have to start buying parts in KSP, will we also have to pay realistic refurb costs? If not, then reusable spaceplanes would have an unrealistic price advantage. If we do have to pay for refurbs, though, then they'd be nothing but toys for the idle rich

Except you're basing all this on real life counterparts, whileas KSP is a computer game and the devs are free to (and no doubt capable) to balance things out. SSTOs currently aren't capable of very heavy lifting (except high partcount monsters made by masterminds) so personally I feel let them be entirely reusable free of charge. Not only does it take longer to take off, get to orbit, deploy payload and then land than it takes to launch a satellite / orbiter, but it's far more challenging as well.

We can draw parallels to real life stuff all we want, but at the end of the day this is a computer game we're playing, mainly for enjoyment. We chuck kerbals at rockets and then the rockets at the sky until we get stuff into orbit, no matter the amount of explosions. There's no need for 100% realism.

[Geschosskopf]

Except you're basing all this on real life counterparts, whileas KSP is a computer game and the devs are free to (and no doubt capable) to balance things out..

No kidding? I hadn't noticed .

Seriously, though, the refurb cost needs to be considered. In any game with pricetags, player choices are limited by the depth of their pockets. So, if spaceplanes are unrealistically cheap compared to rockets, players will be funneled that way whether they like it or not, just so they have enough money to do what they really want.

[Null_Pointer]

There are some advantages that planes have as a launch vehicle.

Probably the most important one is that Jet Engines have a very high fuel efficiency compared to any of the rocket engines and they also have a good TWR. This means that they can lift more mass for less fuel making the whole launch vehicle smaller and more efficient. This lets you get up to around 18k pretty easily (and higher still if you abuse air intakes properly) which you will notice is well above the majority of the atmosphere. It also isn't out of the question that you can get your orbital speed around 1000m/s without too much difficulty and a half way decent space plane. This means that when you switch to rockets you need both less oomph to get into orbit and that the rocket engines will be more efficient as the lower atmosphere means higher ISP (again meaning your craft is more efficient). If we had a better aerodynamic model it would also mean that the lifting of a payload would be aided by the wings, further improving the efficiency of lifting payloads at lower altitudes.

So, if a player had FAR installed (to have a better aerodynamic model that takes account for the lift that wings produce), would a horizontal takeoff SSTO with jet engines have greater fuel efficiency than a vertical takeoff SSTO that also used jets?

[EatVacuum]

This all sounds good in paper but it doesn't work that way in real life, as was discovered with the Shuttle program. It cost more to refurbish the orbiter after each flight than it would have to build a 1-shot rocket to do the same job. And remember, the original plan was to refurbish the SRBs, too, but that very quickly went by the boards due to cost and safety issues. Basically, the Shuttle was a white elephant, all because it was supposed to save money by being "reusable".

Well that's how it worked out using 70s technology by a government organization that was built on the model of a huge bureaucracy funded by continually begging to Congress for more cash. NASA did great things in the 60s when the U.S Government was willing to throw huge wads of cash into the pot so that they could beat the Soviets to the moon and thereby prove that America was the greatest nation, with the best technology. But that doesn't spawn a culture that looks for financial efficiencies. That scenario is however changing with the entry of privately funded, commercial enterprises into the new space race. Private enterprise is all about competition and part of that mean being more efficient than your competitors. To prove that statement, compare the prices for NASA's "old gang" suppliers' various lift system delivery costs vs. the leading private corporation's (costs are per kg to LEO) -

NASA - Saturn V (60s tech) $9,900, Space Shuttle (70s tech) $10,400, Delta IVh (2000s tech) $13,000, (Hmmm, prices are rising, and I believe these are inflation adjusted)

SpaceX (all 2000s tech) Falcon 1e $10,700, Falcon 9v1 $5,360, Falcon 9v1.1 $4,100, Falcon Heavy (still in development) $2,200 (A lot less time in the space game, but a lot of improvement in terms of cost)

Many of the private companies are looking at recycling boosters (which NASA apparently couldn't figure out) and in at least one case their entire rocket, and given private enterprise's rapid progress in just a few years, I suspect they will achieve those efficiencies.

And there are some very promising space plane possibilities out there, as well as non-space plane SSTOs, so your comments will not likely be valid for much longer. For instance, Spaceship One got into low space, and it is just the harbinger of greater things to come, like Reaction Engine's proposed Skylon space plane. It might turn out to be another Concorde (i.e. technical genius but not commercially viable), but the British government and the ESA are convinced enough to invest tens of millions of Pounds and Euros in the Sabre hybrid engine's development.

[codepants]

On the note of the fellow above me, I wanted to throw in my two cents (though despite usurping the justification, I'd say the same thing because this is KSP):

The necessity of reusable spacecraft depends on the way you play. If you have life support mods and a space station you need to re-supply the space station. If you have a launch vehicle for probes oribiting Kerbin you need to reload it with probes. There are loads of reasons you'd want to put something light into space over and over again.

It is all based on cost, which no, does not matter right now, but it will at some point. Things that are currently "counted" in the game aside, it's personally satisfying to do things "right."

Whatever that means.

[Hodo]

I see a lot of "Space planes aren't useful for moving heavy loads into orbit" statements, that is just down right false. I have a space plane SSTO that works in FAR+DRE that regularly hauls up to 72 tons into a 100km x 100km orbit without much of an effort. It for one is great for building a space station at 100km x 100km with as few parts as possible. I have had more success with my SSTO space plane program than my rocket program. Other than my medium and heavy lift rockets which max out at 25 ton lift capacity, the only way for me to get anything that weighs more than 25 tons into orbit is by way of my SSTO space planes. FAR keeps me from building those so common and horrible and not at all realistic asparagus launch monsters of a million and one stages and over 9000! mainsail boosters, that have the same chances as getting into space in the real world as a fat kid sitting on a 2x4 plank throwing a bowling ball on the other end.

While I am on my soapbox....

I have less problems with people who use mechjeb than those horrible asparagus monstrosities of pealing rocket stage launches that have no aerodynamic properties at all. I know it is a game but COME ON try and build something that at least looks like it would work.

But I digress, it is not my place or anyone elses to tell them how to play the game.

So, if a player had FAR installed (to have a better aerodynamic model that takes account for the lift that wings produce), would a horizontal takeoff SSTO with jet engines have greater fuel efficiency than a vertical takeoff SSTO that also used jets?

Actually VTOL SSTO space planes have better efficiency than a "rocket" style jet powered launcher, but are slightly worse than a SSTO space plane that takes off conventionally.

Edited November 15, 2013 by Specialist290
Merging sequential posts.

[Johnno]

Let's not dig up old threads, especially with replies that'd be better suited for Science Labs than Gameplay Questions.

Thread closed.