Do jet SSTOs need wings?

[Vanamonde]

Sure, wings help in the lower atmosphere, but the higher you go the less lift they generate while still imposing drag. And since KSP get engines have a T/W ratio greater than unity, I'm wondering whether one needs to bother with wings at all. So I made this, but I'm having trouble getting it to orbit.

However, that could just be because I generally suck at spaceplanes. So guys who are good with spaceplanes, what do you think? Is this not making it because I'm a bad pilot, or because the concept is flawed?

Craft: http://www./download/hgodfxbellctx53/XSSTO.craft

[Johnno]

As a concept SSTOs don't need wings. You can even build some rockets to be single stage to orbit, without jet engines.

[AnalogAddict]

Looks really heavy. If that is like I suspect and you have an LV-N tucked down in there, you might want to consider replacing that with an LV-T30 or LV-T45. When using jets to assist your takeoff, you're looking at igniting your rockets at an altitude of 16~20km versus 0km on the launchpad so essentially all they are there for is to get your rocket to 20k and moving at some significant velocity. Try removing the all chutes except for 3 or 4 radials, remove the tricouplers and lower total jet engine count to 3. The small 90L fuel tanks you have are fine IMO especially if you are lowering engine count. I personally use 3 intakes; however I leave that to the imagination of op. I've got a similar craft to yours, but the best part of the game is playing with your own designs until they work.

[Vanamonde]

Sorry, I wasn't clear. I'm trying to fly it much like a classic spaceplane, but without wings. Vertical launch, but then more or less level build-to-speed at 20k+, firing the rocket (it's a Skipper, 650 thurst) just before the jets flame out. I don't see how I could remove any parts because it does need all 6 jets just to get off of the pad, and hits the ground like a brick without the 12 parachutes I've got crowded on there now.

And actually, it's at leat failing in the same way all my stupid winged efforts do; I lose too much speed while trying to pitch up from level jet flight to a steep rocket climb. Yeah, I know it's kind of a monstrosity, but I'm curious to see if it can be done.

[ecat]

I've not tried a true jet SSTO using stock parts just some heavy 36km jet lifters. Perhaps I should give one a try.

Using the B9 pack, and especially the dual mode engines, wingless jet SSTOs become trivial, no clipping of intakes required either...

http://forum.kerbalspaceprogram.com/showthread.php/33503-Show-off-your-B9-Designs%21?p=498736&viewfull=1#post498736

http://forum.kerbalspaceprogram.com/showthread.php/33503-Show-off-your-B9-Designs%21?p=501586&viewfull=1#post501586

Those are not wings in the above. People complain about spamming air intakes so I took spam to the limit too see if it could still fly.

.

http://forum.kerbalspaceprogram.com/showthread.php/33503-Show-off-your-B9-Designs%21?p=508910&viewfull=1#post508910

Edit:

You replied while I was typing...

Wings generate lift. Without them level flight sounds very unlikely.

Edited July 10, 2013 by ecat

[Sirrobert]

A spacePLANE type SSTO would need wings yes.

[m4ti140]

Manley's jet launchers from 'Reusable Space Program are pretty much wingless jet SSTOs, you may want to see his design.

[Person012345]

If you have no vertical force, you won't go up unless you achieve orbital velocity (highly unlikely in lower atmosphere).

[Sirrobert]

Manley's jet launchers from 'Reusable Space Program are pretty much wingless jet SSTOs, you may want to see his design.

That one went to orbit like a rocket though, not like a plane

[Cranium]

Just being an SSTO does not require that it needs wings, and it technically doesn't need stabilizers either. Being an SSTO just implies that it is a single stage(no parts being detached) into orbit. For being a spaceplane, of course it would need wings, otherwise it couldn't be classified as a plane at all.

[HoY]

you ONLY need wings to go UP if your TWR is lower than 1.0

You have Much higher TWR than 1.0 so you can climb just fine without wings..

with only 3 intakes per engine however you wont get much higher than 22-24 KM.

I recommend assigning action groups to the engines in pairs, so the higher you get the fewer engines you have running, thus alloting more intake air for the remaining engines.

[K^2]

Here is a minimalist, all stock SSTO with no lift to speak of. Makes it to orbit and de-orbits just fine.

[Vanamonde]

Guys, I'm not asking whether it meets the definition of "spaceplane." I'm wondering how much wing lift contributes to a craft that is already going 1000+ m/s at 20k+ altitude, and whether you really need wings at all to transition from there to orbit. HoY, that is helpful advice, and K^2, I tried something almost identical and couldn't get it to orbit either, which suggests that it may indeed be my piloting that is the problem. And thanks ecat, but the fact that "wingless jet SSTOs become trivial" with mods is one of the reasons I don't like to use mods.

[numerobis]

Lift contributes mostly at low speed, for three main reasons:

1. Lift depends on air density. At 20km, you get 2% of surface air density. Lift increases with speed, but you're not going 50x the speed. So lift gets pretty small.

2. At 1 km/s you have double the thrust you had on liftoff (and double what you will have at 2 km/s). So you can get substantial lift just by pointing your nose up.

3. Eventually you're going so fast your plane doesn't get around to falling before the ground is gone. This replaces your need for lift.

So if you have TWR below 1 on liftoff, you need wings; otherwise, you don't.

Landing is trickier if you don't have wings.

[HoY]

I'm actually spending most of my time this week building and flying wingless hybrid rockets, very small and light but that carry 6000m/s of dV and a single satellite to orbit. Just today I did the launch twice and put one around both eve and Gilly, in preparation for my first Eve launch vehicle test. (ISA and Kethane satellites, for refueling before landing And for landing on a high mountain)

To be completely honest, hybrid rockets(or ssto's as many people usually call them) Are very easy with 100% stock parts. As soon as you get the hang of it it's just a simple matter of deciding where you want to go as soon as you get into orbit.

Today I even figured out the numbers I need to punch into mechjeb to get a 80by30 orbit on jets in less than 10 mins where as before I had to do the launches mostly manually due to the unique launch profiles

Edited July 11, 2013 by HoY

[Vanamonde]

Thanks numerobis, I think that answers my question; past a certain atlitude, everything becomes a rocket in effect even if it does have wings, so it should be possible to dispense with the wings. (And I'm planning to land it with chutes, so that shouldn't be a problem.)

　

　

Edited: HoY, I'm not using the jet-as-rocket-stage approach because of the difficulty of generating any real speed with the fuel-efficient jets before you pass through their effectual altitude. Hence, the plane-like ascent but without wings.

Edited July 11, 2013 by Vanamonde

[stupid_chris]

Not necessarily, this is an SSTO:

Now is it the most efficient way? I doubt so. Jet engines are obviously the way to go to make an efficient SSTO. But I think someone should study the differences wing/no wings. I mean, a plane spends an awful lot of time in the atmosphere building speed, and has much higher drag losses than a rocket. However a rocket probably has much more gravity losses because it burns against gravity and has no lift. It's a good question, I'd be interested to see numbers.

Edit: oh I misunderstood your question. Well I'm doubtful that wings generate much lift anymore at high speeds in the upper atmosphere. That would need to be tested out too I guess.

Edited July 11, 2013 by stupid_chris

[HoY]

Jet-as-rocket stage isn't how I use them either. I use it like a spaceplane that takes off vertically and climbs to 9km before I start the horizontal flight, due to terminal velocity being so low below 10km. Between 20 and 30km my flight path is nearly horizontal, and the only actual vertical speed I still use is momentum from before I turned over. By the time I have an actual periaps my vertical speed has nearly all bled off and I then just increase it by raising the nose a hair.

I don't use them the way Scott Manley uses them, basically glorified SRB's on his launcher. If I put jets on something I use them to their fullest extent. To the extent that I only get 1kn of thrust from the last firing engine at 65km trying to get that PE up as high as I can before I have to switch to the LFO engines.

Here's a couple of my earlier hybrid designs, had posted them on the spacecraft exchange. They are 100% re useable designs, meant for bringing payloads up and down from Laythe's surface

http://forum.kerbalspaceprogram.com/showthread.php/28431-I-Present-the-Firebat?highlight=Firebat

The first post describes the ascent profile, which is still pretty much how I do it now, tho a little less sloppy now

Edited July 11, 2013 by HoY

[Vanamonde]

That sounds like what I'm trying to do, Hoy, but I'm using the 3-man capsule because I want it for crew rotations in orbit.

[HoY]

The firebat I linked there was just a 1 man capsule, but it can easily carry another 10-12 tonnes into orbit, I only used a lighter payload because it needed the dV to make it to Laythe without refueling. A larger version like the Marauder (a crude attempt at a 45t ssto but effective) can bring up a small station in one launch lol.

Point is, yes it's quite feasible to use jets to get almost completely into orbit with even heavy payloads. I've seen some that can carry more to the order of 80t into orbit, tho those are more complex and time consuming to fly that is worth it IMHO.

Even the 45t marauder was slow to fly due to the massive part count incurred by spamming air intakes.