Upper stage SRBs (PAMs etc.)

[marach]

Wonder if a mod can use the fuel in an srb for a surface attached motor be interesting to see a collar that acts as a brake for SRB's when staged...

[moogoob]

1 hour ago, wumpus said:

Kerbal (mad science) suggestion: bring sepratrons.  Bring pairs of them and use them for correcting burns.  Trial and error will be needed to perfect this, but I suspect that you should be able to fix your burns midcourse (note that you might need sepratrons that aren't full). [Side note: I have to try this...

I did this once - put three or four pairs of Separatrons for the final circularization into orbit, then fired them as needed. I don't think I even needed the last pair. It wasn't a good orbit, but it was an orbit, all right.

[wumpus]

On 2/25/2016 at 2:23 PM, regex said:

This.  Using a PAM requires planning and foreknowledge.  Even on RO/RSS, I'd also have backup engines/RCS on my payload to make corrections as needed as the PAM tends to be slightly inaccurate.

No kidding.  I built two craft, the first the "workable PAM" I suggested for a specific contract "escape Kerbin".  It worked fine (One stayputnik, one hammer, one BACC thumper, some fins (on both stages) and a launch clamp holding it at an angle).  Went inside Eve's orbit (doing science with such a craft is an exersize for the reader).

I built a similar rocket (replaced the stayputnik with an octo probe, added sepratrons, added a decoupler between the hammer and octo (no problems letting the hammer escape kerbin), a small nosecone and some solar panels).  This got within a few ~200,000 km (guessing the thing switched to km for encounters) of Eve, but used three separatrons to escape Kerbin, and left me one for corrections.  Oddly enough, the last correction I needed almost exactly the same delta-v as the last sepratron, but was extraordinarily picky.  I would need a much better launch and many more sepratrons.

I think my biggest problem was controlling the ejection angle.  As you might guess, my primitive spacecraft never bothered with a parking orbit and blasted straight at Eve, New Horizons style (it also left at a ~45 degree ejection which is "close enough" considering the burn but not what you would do with a liquid rocket (or even if you had more torque.  I stuck to "hands off" launching for this one).  The best way to control this would be to carefully handle the launch time (like a real rocket with a proper countdown...).  Once that was done, some sort of 3rd stage (other than my 4 sepratrons) would be needed.  Possibly just a modular girder with a decoupler and sepratrons, or possibly a flea (detuned, an early 3 stage probe nearly made Moho's orbit).  Only then could you use a cluster of sepratrons to manage an encounter (and still require more patience than I have).

[FlyingPete]

One of the more novel uses of an SRB I've seen (can't remember whose design it was) used a BACC as a mid-ascent booster and structural component of an all-liquid fuel spaceplane. The idea being that at the point were the jet engines are starting to tail off, but the nukes aren't good enough by themselves, the SRB fires to give sufficient boost to speed/altitude, getting through the dead-zone. Plus you then have a long, sturdy and relatively lightweight structural fuselage in the middle of the plane.

[RW-1]

I like using sepatrons as de-orbit motors for my kerbin station escape pods, nice and light, provided that I kept the station at an orbital alt that the resultant m/s change bring it into the atmosphere far enough the first time hehehe ,,,,