Circularizing a second stage while recovering a first stage

[dlrk]

I've built a falcon style rocket that has a recoverable first stage and a second stage that enters orbit. Is there a mod or anything to place the second stage in orbit so it doesn't reenter while the second stage is being recovered?

[Reactordrone]

The stage recovery mod will collect the first stage while you control the second but I'm not sure about the other way around. When I've done stock first stage recovery in the past I've just had locked off fuel tanks in the orbital stage so it has just enough fuel to fly high enough to allow first stage recovery before that stage returns to the atmosphere.

Edited July 4, 2016 by Reactordrone

[bewing]

Other than the stage recovery mod -- in stock KSP you always have a little bit of time before the first stage gets back down to 25km and gets autodeleted. Sometimes that's enough to get your upper stage into orbit before you have to switch focus. Sometimes you can recover the first stage fast enough that nothing bad happens to the upper stage while you are gone -- even if it is still suborbital. It's certainly not an optimal way to handle it, but with a little pain you can usually do it.

[dafidge9898]

Yes! It's a mod, and a very helpful mod called FMRS

Here't the link: 

 

[fourfa]

There are some techniques to 'ghost ride' the second stage while you land your booster.  It'll take a lot of practice.  Lock off whatever tanks you need for your payload/mission, plus some extra to handle circularization.  Tweak your thrust rather low, lock the second stage on prograde, start the engine, and switch to the booster.  It will continue firing until out of fuel.  If you tweak everything just so, it will push its apoapsis pretty much to the opposite side of Kerbin, giving you time to land the first stage and switch back to the second stage before it passes apo.  Might need to tweak the thrust back up and unlock your circularization fuel supply.  And it probably won't be an ideal low-dV burn.

edit: you have to wait to start your separation and payload burn until you have crossed into space.  Otherwise you'll get deleted.

Edited July 24, 2016 by fourfa

[KerikBalm]

Its quite hard, you have to get a pretty high apoapsis before stage seperation.

I made a recoverable flyback booster... but it wasn't so efficient... I might as well have SSTO'd it (would have been different if I let it land downrange, rather than including the fuel to reverse the booster's flight... poerhaps flying back on airbreathers would be better)

^ Booster burning retrograde, apopasis above the atmosphere so at the end of the burn I can switch to the orbiter.

Circularize... and then switch back before the booster reaches 25km and despawns (I think its 25)

Didn't land down the centerline, but rolled onto the runway for 100% recovery

 

This is an example of a failed recovery trajectory:

because:

the apoapsis for the booster fell below 70km, and thus once the other one is over 2.5km away, I get the "can't switch vessels while in atmosphere" message... and the orbiter will fail to orbit before i can land the booster.

... the only option would be to circularize the orbiter well before it reaches apopasis so that I can switch to the booster before the booster falls to far... but then that results in a funky non-circular orbit, or a burn with a significant anti-radial component which is inefficient... and I was already cutting margins thin to try and get the best economy possible... it was still about 400 something funds per ton to orbit IIRC... and considering disposables can get below 600... its not so much savings, even if everything always goes perfectly.

 

Edited July 21, 2016 by KerikBalm

[carlorizzante]

Not sure if that's useful but if you have RemoteTech and a probe core on the shuttle you can instruct the shuttle to auto-execute the maneuver to circularize, so that you should be able to take care of the first stage, 'cos the shuttle will take care of itself.

[Vive_moi]

1 hour ago, carlorizzante said:

Not sure if that's useful but if you have RemoteTech and a probe core on the shuttle you can instruct the shuttle to auto-execute the maneuver to circularize, so that you should be able to take care of the first stage, 'cos the shuttle will take care of itself.

Hello,

It will possible, only if your payload stay in the physic bubble, i.e. no more than about 20km away of the first stage. (I use this function for multiple orbital function, but never try this one.)

 

See you,

Vive_moi

 

Edited July 21, 2016 by Vive_moi

[carlorizzante]

1 minute ago, Vive_moi said:

Hello,

It will possible, only if your payload stay in the physic bubble, i.e. about 20km. (I use this function for multiple orbital function, but never try this one.)

 

See you,

Vive_moi

 

Good objection. Usually I rely on the Stage Recovery mod to save the first stage, and on the exec function of RemoteTech to execute maneuver nodes for probes ('cos it makes more sense to me that way). So I never switch back to the first stage to guide it home.

But I guess that as long as the shuttle has a probe and/or a crew on board (and perhaps achieve a stable orbit before going out of the "physic bubble") it should be fine.

Perhaps I should try just for fun.

[Vive_moi]

Be careful, the RemoteTech Flight Computer will only work with... a Flight Computer aboard.

So, even if you vessel is crewed, you'll need a probe core to use the automated RT maneuver. (There is no flight computer in the crewed command modules. A mod for this ?)