Vertical launch of spaceplanes?

[tjsnh]

I have serious trouble launching a space plane vertically on top of a rocket.

The lift from the wings flips the rocket over and makes the assent entirely uncontrollable, and it still happens of the entire spaceplane is inside a fairing.

Anyone have experience resolving this issue?

[Foxster]

I'm surprised it still does it inside a fairing - that's what fixed the last one I flew.

You could try putting some huge fins/control surfaces on the lower part of the lifter. You can also try mixing things up and dragging the space plane up by attaching it to the bottom of a lifter.

Edited June 6, 2015 by Foxster

[serolrom]

You seem to have the answer.

I'm no expert, even less with space planes, but I finally got mine up there. I had to deal with that problem among others.

The key is, as you alread noticed, to have the aerodynamic surfaces UNDER the center of gravity, and so the thing goes from flipping to stable.

Now ow the difficult thing is, how to do that. This is where engineering and imagination comes to play.

[cybersol]

In the tutorial section, there is a how not to get things to FLIP sticky thread. I posted about a similar problem & fix there, repeated below:

Finally, a different class of problems comes when hauling things with their own lift to orbit. Here I am lifting my standard nuclear tug. I like this configuration with 2 wide nukes, because they are stackable (need more TWR, just add more tugs), *limited by wobble. However, the wide arrangement doesn't fit in a fairing, so I had to overcome the lift generated by the radiators fins. Here I used 4 delta wings generated enough lift below the CoM to offset the lift in the upper stage. The launcher is my medium 3 mainsail rcoket SSTO.

TL;DR = Use lift surfaces at the bottom to move the center of lift far below the center of mass, even when the upper tanks empty the CoL needs to stay below the CoM

Edited June 6, 2015 by cybersol

[Murph]

NASA Shuttle-style can work quite successfully. Beyond that, you just have to make sure that your nose is never too far from prograde below about 25,000m, and that you have sufficient control authority (control surfaces, thrust vectoring, and reaction wheels). Launching with it on the top of the rocket, as shown in the pictures, is probably the more difficult option, and will likely need significant tail fins (i.e. probably actually wing sections used as tail fins, of equal or greater surface area than the wings of the plane). Launching Shuttle style, the issue of wings at the top mostly goes away, and you just need to consider centre of thrust vs. centre of mass (which doesn't have to be perfect, just not so far apart that it's creating a huge turning force).

The other issue you could be facing, is not aerodynamic force from the wings inside the fairing, but aerodynamic force from the fairing itself. Fairings do not get rid of drag, they just smooth the flow and minimise it for the size. A HUGE fairing still has large drag. The issue could be that the fairing is creating so much drag at the top of the rocket, that it's actually the fairing pulling the nose over. A big fairing has a big surface area; big surface area presented to moving air results in big force.

[Mic_n]

That's where the buttons in the lower left come into play.. Centre of Mass, of Lift and Thrust (can't remember the order). With a plane on top of a rocket, you're generating lift (and drag) up there, with all the weight at the bottom. That's a sure-fire recipe for disaster. You need to get your centre of lift back behind your centre of gravity(/mass) and keep it there.. don't forget that without intervention, fuel burns from the furthest source first. That usually means the top, and it means your centre of mass shifts backward as you burn.

Considering the weight of the engines, it can be rather difficult to keep your mass anywhere but at the bottom, so you need your centre of lift to be back there too. A fairing to cover it is still going to be causing a lot of drag and trying to flip you over.

Basically, you need wings at the back, and they need to be creating more (significantly more) lift than those at the front.

But...

There's an alternative solution here.

Your payload (the plane) need not be mounted on top.

Maybe you could radially attach it lower down.. though you'll need to compensate for asymmetry then. You could also stage radially off it.. it's less effective with the new aero, but the old 'asparagus staging' can inspire a winner here, letting you mount stages on belly and dorsal surfaces (symmetric there) as well as wingtips. More drag than a single candle, sure.. but it helps keep things in check.

Basically, think a bit more 'space shuttle'. That's a damn tricky design to recreate in itself, but take it as inspiration.

Also Foxter... is that thing going to Laythe or something? Awful lot of dV you have there for not a whole lot of payload.

[Foxster]

Also Foxter... is that thing going to Laythe or something? Awful lot of dV you have there for not a whole lot of payload.

It's going to the third star on the right and straight on till morning i.e. I built it first and the destination will come later

[Skorpychan]

How do you get the fairings to go out and around thing, without having to use parts to get the base that wide?

[moogoob]

Yup! I used two identical Skipper boosters, one ventral and one dorsal. (see first and last image in this gallery:)

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In this setup, the centre of drag stays behind the centre of mass the whole trip. The alternative is putting an absurd amount of wings on the bottom of the rocket, and/or an absurd mushroom fairing.

EDIT: I wouldn't really call it a spaceplane though - it's a "shuttle." Vertical takeoff, horizontal landing, like NASA's shuttle or Buran.

EDIT again: You can download that craft from the link in my sig if you want to play around with it.

Edited June 6, 2015 by moogoob