[Test Results] How much wing does your SSTO spaceplane need? Answer: Maybe none at all.

[A_name]

Abstract:

I've seen a tendency amongst people on the forums struggling with their SSTO spaceplanes of overestimating the amount of wing they need. So I ran some tests to show you can get a spaceplane into orbit and back safely without even needing wings.

Stuff:

• This experiment was performed followig the Kerbal scientific method, so it's solid science.
  
• I'm not saying that the best way to build an SSTO spaceplane is with no wings. I just want to show that wings are overated.
  
• I know you can "cheat" a wingless body into flight with enough thrust. Since I'm no dirty cheater, I did all my takeoffs with reduced throttle to keep TWR under 1 (more details below). The reduced throttle was only to show that the test planes were capable of stable flight. I sobsequently throttled back up for the ascent into space. Also note that spaceplanes need high levels of thrust anyway to break the sound barrier, so I think these test planes fairly reflect how an average spaceplane performs.
  
• I used Mk2 parts because they seem to have the most body lift. I hope that isn't cheating.
  

The tests:

Below is the first test craft, a minimal spaceplane with the smallest wing part appart from the basic fin.

It takes off with no problem at 89 m/s, which is a pretty decent takeoff speed. Note the body lift and the TWR whch is at .66.

Second test craft, this time with no wings.

What do you know, this one took off at 89 m/s too, although I did have to throttle up a bit more. TWR=.75.

OK so far so good, but can it space...? Let us find out.

It can space, but sadly it can't orbit.

It can fly a decent reentry profile though.

It glides reasonably well for a wingless craft.

This counts as a landing right?

Third test craft. Upping the bet with a much heavier vehicle and the extra fuel should be enough to get into orbit this time. I also added some extra control surfaces to balance the center of lift.

I had to drop this one off the end of the runway to get airborne with the TWR below 1, but we're flying. TWR=.59.

This is perfectly safe.

We have orbit. Now to land it.

I totally chose this angle of descent on purpose to test the plane's ability to brake out of the dive and glide safely to a soft landing and not because I'm a bad pilot. Oh and I had to use some fuel to maneuver back after overshooting, but that was also on purpose.

Success.

It's past my bedtime now so I'll be signing off. Hopefully this is useful for somebody.

[Grumman]

I built a few similar planes in 0.90, including the Jart SSTO:

I wasn't trying to make a wingless SSTO, but one that could be delivered to Laythe in a Mk 3 Cargo Bay.

[tbarcello]

I built a few similar planes in 0.90, including the Jart SSTO:

http://i57.tinypic.com/2rf79dz.jpg

I wasn't trying to make a wingless SSTO, but one that could be delivered to Laythe in a Mk 3 Cargo Bay.

Ooooh, that's a beauty!

[Superfluous J]

So the answer to "how many wings do you need?" is none. You need none wings.

[tbarcello]

So the answer to "how many wings do you need?" is none. You need none wings.

Yeah. But i mean, pretty obvious, ain't it? If i launch a rocket and it has enough to reach orbit in one stage and has enough chutes and shield to land back in one piece, - that's an SSTO right there.

[cantab]

This is a bit of a con though. True there are no "wings", but there are still plenty of lifting parts. More interesting would be what the minimum amount of lift is. For ascent we know it's zero because rockets can SSTO, re-entry and a targeted landing is the real challenge.

[zarakon]

Mk2 parts ARE wings

[RocketBlam]

So the answer to "how many wings do you need?" is none. You need none wings.

- - - Updated - - -

This is a bit of a con though.

I wouldn't call it a "con". He didn't say it didn't have any lifting parts... that's what makes it interesting.

[GoSlash27]

A_Name,

While it is true that you don't "need" wings to achieve orbit, they do help to make a spaceplane more efficient, particularly when you don't have your spaceplane spammed with engines.

Wings produce a lot less drag than fuselage sections cocked up at high incidence angles to produce the same lift, so if you have sufficient wing area you can go hypersonic at very low thrust, which means higher efficiency.

It's not possible to do this without wings, although if you cram on enough engines you will eventually achieve orbit.

This is an example of what can be achieved with wings:

Compare and contrast the fuel expenditure for the payload to orbit with the wingless designs above.

Best,

-Slashy

Edited September 3, 2015 by GoSlash27

[tbarcello]

A_Name,

While it is true that you don't "need" wings to achieve orbit, they do help to make a spaceplane more efficient, particularly when you don't have your spaceplane spammed with engines.

Wings produce a lot less drag than fuselage sections cocked up at high incidence angles to produce the same lift, so if you have sufficient wing area you can go hypersonic at very low thrust, which means higher efficiency.

It's not possible to do this without wings, although if you cram on enough engines you will eventually achieve orbit.

This is an example of what can be achieved with wings:

http://i52.photobucket.com/albums/g13/GoSlash27/CamachoII_zpsxstt1iyy.jpg

Compare and contrast the fuel expenditure for the payload to orbit with the wingless designs above.

Best,

-Slashy

No way! It flies to orbit?!

[Stoney3K]

No way! It flies to orbit?!

Apparently the current record holder is >20t of payload on a single engine. That plane was a massive delta wing though...

[tbarcello]

I know I'd never be able to get it to orbit. Guess it takes some massive skill.

[GoSlash27]

I know I'd never be able to get it to orbit. Guess it takes some massive skill.

Not really. I'm working on a design now that lifts 37t of LF&O to orbit on 4 RAPIERs at over 30% mass efficiency. The takeoff procedure is pretty much "maintain 5° pitch".

Best,

-Slashy

[tbarcello]

Not really. I'm working on a design now that lifts 37t of LF&O to orbit on 4 RAPIERs at over 30% mass efficiency. The takeoff procedure is pretty much "maintain 5° pitch".

Best,

-Slashy

Impossiburu! I am struggling with passanger liquid fuel only one... Well, not anymore, but was...

So you are saying " puck the thrust, just get wing", or what?

[Starhawk]

Impossiburu! I am struggling with passanger liquid fuel only one... Well, not anymore, but was...

So you are saying " puck the thrust, just get wing", or what?

He's saying that a given amount of engine can achieve more payload to orbit with wing than without. You don't need huge thrust if you get help from wings.

Happy landings!

[GoSlash27]

Impossiburu! I am struggling with passanger liquid fuel only one... Well, not anymore, but was...

So you are saying " puck the thrust, just get wing", or what?

tbarcello,

Well... not necessarily. There's a lot of different ways to make SSTOs. I'm just saying that you won't make an SSTO that's worth a darn unless it either has high thrust, adequate wing loading, or some combination of the two.

While it is true that you don't "need" wings for an SSTO spaceplane, you do need wings if it's a low t/w spaceplane.

Best,

-Slashy

[A_name]

So the answer to "how many wings do you need?" is none. You need none wings.

Under some circumstances, yes!

Yeah. But i mean, pretty obvious, ain't it? If i launch a rocket and it has enough to reach orbit in one stage and has enough chutes and shield to land back in one piece, - that's an SSTO right there.

Yes, which is why I made a point in showing you can get off the ground even with a TWR less than 1, which a rocket can't do of course. This was acknowledged in the "Stuff" section. This is also the reason why I keep saying "SSTO spaceplane" instead of just SSTO. The main point of this was to show that if you are inclined to build a spaceplane (instead of a rocket SSTO) you can get away with using very little wing.

This is a bit of a con though. True there are no "wings", but there are still plenty of lifting parts. More interesting would be what the minimum amount of lift is. For ascent we know it's zero because rockets can SSTO, re-entry and a targeted landing is the real challenge.

Yes, I mentioned this in the "Stuff" section too. This is aimed at people trying to build SSTO spaceplanes. Also, rocket parts produce body lift of their own, although admittedly less than the Mk2 parts. Targeted reentry and landing is indeed the biggest challenge of a rocket SSTO in my opinion.

Mk2 parts ARE wings

That's true. This is for people who put more wings on the wings, dawg. I'm getting a feeling people don't read the Stuff.

A_Name,

While it is true that you don't "need" wings to achieve orbit, they do help to make a spaceplane more efficient, particularly when you don't have your spaceplane spammed with engines.

Wings produce a lot less drag than fuselage sections cocked up at high incidence angles to produce the same lift, so if you have sufficient wing area you can go hypersonic at very low thrust, which means higher efficiency.

It's not possible to do this without wings, although if you cram on enough engines you will eventually achieve orbit.

This is an example of what can be achieved with wings:

http://i52.photobucket.com/albums/g13/GoSlash27/CamachoII_zpsxstt1iyy.jpg

Compare and contrast the fuel expenditure for the payload to orbit with the wingless designs above.

Best,

-Slashy

Thanks for chiming in dude! I shall try to get a similar design with no wings into orbit! And yes, like I mentioned this is NOT the best way to make a spaceplane. Proper wings WILL help you lose less Dv to gravity drag, plus they make the plane more controllable, especially if your reentry isn't spot-on. It's more of a test of concept.

- - - Updated - - -

tbarcello,

Well... not necessarily. There's a lot of different ways to make SSTOs. I'm just saying that you won't make an SSTO that's worth a darn unless it either has high thrust, adequate wing loading, or some combination of the two.

While it is true that you don't "need" wings for an SSTO spaceplane, you do need wings if it's a low t/w spaceplane.

Best,

-Slashy

^^^This.

[xtoro]

Wouldn't an SSTO spaceplane without wings be just an SSTO rocket that launches horizontally? I mean, planes have wings right?

[A_name]

Wouldn't an SSTO spaceplane without wings be just an SSTO rocket that launches horizontally? I mean, planes have wings right?

Hahaha that's a good point. We can call it a SSTOJAHLBDR, which I think rolls of the tongue quite nicely (single-stage-to-orbit-jet-assisted-horizontally-launched-lifting-body-rocket).

- - - Updated - - -

I built a few similar planes in 0.90, including the Jart SSTO:

http://i57.tinypic.com/2rf79dz.jpg

I wasn't trying to make a wingless SSTO, but one that could be delivered to Laythe in a Mk 3 Cargo Bay.

Very ingenious design dude. Way to get all those lifting surfaces to fit in there while keeping it balanced and looking nice. I like it a lot!

- - - Updated - - -

Not really. I'm working on a design now that lifts 37t of LF&O to orbit on 4 RAPIERs at over 30% mass efficiency. The takeoff procedure is pretty much "maintain 5° pitch".

Best,

-Slashy

That would be 1 orange tank, right? Although knowing your designs, I suspect you won't be carrying all that fuel in an orange tank but rather distributed throughout the craft. It'll be interesting I'm sure!

Edited September 3, 2015 by A_name

[GoSlash27]

That would be 1 orange tank, right? Although knowing your designs, I suspect you won't be carrying all that fuel in an orange tank but rather distributed throughout the craft. It'll be interesting I'm sure!

A_Name,

Most of my stuff is pretty uninteresting, actually. For me, SSTOs are just glorified short haul delivery vans.

So in the case of this one, it merely exists to transport fuel to orbit and transfer it through a docking port. No reason to waste payload on an actual tank just to leave it floating up there.

The only reason I mentioned it is because it's not difficult to fly at all despite being large and ridiculously underpowered.

Best,

-Slashy

[GoSlash27]

Update:

Flight of the Brawndo:

http://s52.photobucket.com/user/GoSlash27/KSP/Brawndo/story

No way this behemoth is gonna get supersonic on just 4 engines, right?

Except it does. And this is just before I switched to closed cycle.

The trick is drag management. You see... it's not the thrust to weight that keeps you from going supersonic, it's the thrust to drag. So if you build it clean you can do more with less. And the wings are critical because they allow you to keep the fuselage aligned with the airflow without falling into denser air.

Wings create very little drag even when they're angled up at a very high incidence. Fuselage parts, OTOH, create a lot of drag even when they're not misaligned very much. So it's worth it from a drag standpoint to use wings to create your lift instead of the fuselage.

This can all be bypassed if you use a lot of thrust to weight because you jump out of the atmosphere so quickly that drag isn't really an issue. But you pay a price in efficiency from having so much of the mass you carry to orbit being engines.

Best,

-Slashy

[ajburges]

Given the nature of the missions tankers take, I would just optimize them for a fast, fool proof flight. 12 mins to switchover is quite the wait. Given how plentiful funds are, I'm leaning towards the belief that pilot time to volume is the most important metric of any refueling mission.

Save the optimal flight envelopes and paths for unique missions: module delivery and SS beyond MKO.

Edited September 3, 2015 by ajburges

[Starhawk]

I've been seeing 30 tonne/Rapier designs in the Stock Payload Fraction Challenge lately, as well.

Amazing how far the state of the art has come since the aero overhaul.

Great work, Slashy!

Happy landings!

[GoSlash27]

Given the nature of the missions tankers take, I would just optimize them for a fast, fool proof flight. 12 mins to switchover is quite the wait. Given how plentiful funds are, I'm leaning towards the belief that pilot time to volume is the most important metric of any refueling mission.

Save the optimal flight envelopes and paths for unique missions: module delivery and SS beyond MKO.

ajburges,

I'd be inclined to agree, but as a practical matter how much real time is it going to take to deliver 38 tonnes of fuel to a station with a faster spaceplane? And what's the part count? How much will that slow the experience down?

I think it's worth it to take the slow boat to orbit in the long run, everything considered. You still have to match inclination, intercept, rendezvous, dock,transfer, undock, retroburn, deorbit, and land once for every flight and delivering fuel to orbit is a regular evolution. That takes a huge amount of time, especially when the payload is small for each flight.

The amount of time spent in the ascent to closed cycle is miniscule in comparison with the time spent flying an entire mission and if you have to do just one more trip to transfer the same load you've just wasted way more time than you ever could have saved with a faster ship.

In this case, it took 1 hour and 6 minutes game time to deliver 38 tonnes. Using faster means I could shave off maybe 6 minutes, but it either won't be the same payload mass (meaning I have to do another mission) or else it will reduce the frame rate to a still-life,cost a whole lot more, and not actually save any time.

A few extra minutes to deliver a large payload without frame lag is worth it in the long run IMO.

YMMV.

Best,

-Slashy

Edited September 4, 2015 by GoSlash27

[sardia]

Slashy, I noticed you used tilted adapters and nose cones, is that to get it to align with the mk3 body? Aka, does that reduce the drag you were talking about?