Space Planes. Why, why bother?

[Redshift OTF]

You can make lifters and landers using jet engines so a plane shouldn't be too much trouble, (theoretically). Perhaps uou should build a rocket out of jet engines to experiment with optimal flight paths and then move onto planes.

[briansun1]

Hi Folks,

It's fair to say that, despite a number of efforts at scrath building a space plane, I can get them into orbit with enough fuel to circularise, or to go about docking.

I think my design is alright, usually enough fuel to hit 1000m/s at 20km in horizontal flight, then enough fuel to reach 80km LKO, but never enough to circularise. Not sure if it's the design, thrust, flight profile. So anyway, two questions.

1. What are the key rules about space plane construction (I usually try to balance CoL over the CoM, but really not sure if that's right) to get best lift and best stability?

2. Why on earth should I be building this sodding plane given I can reach orbit in under 4mins with no fuss using a capsule? Maybe when budgets come into it having a totally reusable vehicle would be helpful, but the hassle of launching the thing at the moment seems not worth it.

Cheers,

Os

1.If you do that is more manuverable but generaly you want CoL slightly behind CoM

2. For fun. though generaly when I make a space plane it's not an SSTO

[Gauss H2K]

Hi Folks,

1. What are the key rules about space plane construction (I usually try to balance CoL over the CoM, but really not sure if that's right) to get best lift and best stability?

2. Why on earth should I be building this sodding plane given I can reach orbit in under 4mins with no fuss using a capsule? Maybe when budgets come into it having a totally reusable vehicle would be helpful, but the hassle of launching the thing at the moment seems not worth it.

1)

a) Try to build an aircraft that has all its fuel at it's CoM, or moves the CoM forward while draining, this makes transitioning from flying full to empty much quicker.

You want control surfaces to be set up like a real world aircraft for better performance. This means ctrl srfs inline with CoM but out to the side controlling roll. Either ctrl srfs far behind, or far forward in front of the CoM (The greater the distance the greater the control due to torque), These control pitch. If using FAR I'd recommend either a forward canard or a rear canard that alter it's shape as going super sonic causes the CoL to shift back, potentially nullifying any elevators back there. Finally you want a ctrl surface inline with the CoM but as far behind, and acting as rudder, controlling yaw, or side to side movement. From personal experience the yaw and roll ctrl srfs are mostly used to stabilize, or steer. The pitch is where the majority of your flight will be controlled and special attention should be given to those ctrl srfs.

c) Drain excess oxidizer from your space plane in the hanger as extra LF means more fuel for air breathing engines, whereas excess O means dead weight. My advice is to use LFO tanks only instead of LF tanks, as they usually have better Fuel to mass ratios even with all the O drained, and they allow the potential to be refueled to allow your space plane to have more fuel while in space.

2) The answer to this question is the same reason anyone does anything in KSP. They do it for the fun/challenge/roleplay/whatever, it all boils down to we do it because we want to. I personally like doing things this way because Space Planes are kinda Sci-Fi like the x-wings that just go into orbit or wherever and can land on anything they want. They only thing they lack upon returning from something is just fuel, which makes them cool.