Build a booster for my mini shuttle !

[AeroGav]

There's a new shuttle challenge,  I had an idea for a small shuttle.    The airplane stage wasn't hard for me to build, and it flys nice - holds prograde more or less by itself , generates optimal lift/drag ratio when in prograde hold , thanks to incidence angle on wings.

I had the idea of putting a kickback on each wingtip to get the thing halfway to space.   That's the easy bit right?  Well, no.    After I'd finished getting hung up on my own launch clamps,  then the torque from the boosters sending me pitching up or down into a half loop crash,  i  found that the flight profile you get with solids doesn't play nice with the lift from the wings.

On the solids, it accelerates harder and harder as the flight goes on due to fuel burnoff, we end up generating too much lift and steadily pitching up into a vertical climb, or even going over vertical.     So we need to not build speed too fast down low, but we still need enough thrust in the first 15 seconds or you get another comedy takeoff.

So, I'm starting over with liquid fuel boosters,  since when has any shuttle program ever been about saving money anyway?      Though i might need more than a pair of Reliants to get the job done...

Here is the mini shuttle with a fail-tacular solid booster setup.

https://www.dropbox.com/s/i9myyrt0vsj7v7s/Starswift micro shuttle.craft?dl=0

What it really needs is something that gets it to 15km+ at mach 3 or more,  in a shallow climb (less than 15 degrees of pitch) - that way the upper stage isn't wasting it's meagre thrust against gravity for long, and is actually thrusting horizontally with some atmosphere to make lift from the wings.

Basically the ascent the upper stage wants to follow looks something like this - 

 

[bewing]

Looks like too many launch clamps to me.

Needs a little more oomph, too.

And when you launch like this, you will always lose a little altitude right at the start, so you need to raise your ship up near the roof of the building, so you have a little room to fall at the start.

Looks like this mostly meets your specs:

https://pastebin.com/raw/B12Xtn5i

 

 

Edited August 21, 2017 by bewing

[mk1980]

I used some "mini shuttles" in an earlier career i played (i think in game version 1.05 or so?). the concept probably still works. might even work better now since we don't really need actual struts (or fuel lines) to get those jobs done.

those shuttles were used to ferry tourists to orbit or to the 2 moons of kerbin. the simple version basically relied on its internal fuel storage after the kickbacks burned out, so it was mostly used for orbit contracts. the more expensive version with the additional terrier pods had enough dV to land on minmus and return. i also had a modified configuration with 3 boosters arranged with triangle symmetry around the shuttle which had enough dV for a mun landing.

simply launching vertivally with the slapped on pair of kickbacks on the tips of the wings worked fine, actually. the control surfaces of the shuttle were enough to force the kickback into some sort of (messy) gravity turn.

was a rather successful design. fairly cheap and reliable. the orbiter part had a total value of ~15k funds, so landing it within the general area of KSC (plus minus a hundred km or something) recovered about half of the total mission cost.

i think i also experimented a bit with angling the whole thing 5° forward at launch, but i gave that up after a few tries. vertical launch and forced gravity turn worked for me.

 

 

[Spricigo]

Wing incidence make a vertical launching 'interesting'. Some ideas:

1.no incidence. One less aerodynamic force to counter.

2. Wings on the boosters with negative incidence.

3.Put the whole thing inside a fairing, on top of a rocket with a lot of tail wings. 

 

 

[AeroGav]

This is what I have so far :

https://www.dropbox.com/s/kmb0b7gqauoomwe/STARSWIFT2.craft?dl=0

Four Reliants, Four Terriers and two Fleas.

After getting established in a steep climb at a reasonable airspeed,  two of the decouplers fire to drop a diagonally opposed set of Reliants (and the empty Fleas that are stuck to 'em).  This reduces our TWR to something that keeps speed growth under control when in a climb like this, so the plane doesn't try to loop over.

At around 12-13km, I stage again, dropping the remaining Reliants, we're now on the four Terriers (which run efficient at this alt).

Booster separation.     It's lower and slower than ideal, the upper stage wastes quite a bit of it's 6k delta V finishing the journey to orbit, but still has over 3000.    If you can get over mach 3,  freefall is supporting half the plane's 20t weight, which means you can get higher where drag is less etc.

Edited August 21, 2017 by AeroGav