SSTO fueling question

[Evanitis]

I want to launch a very stupid SSTO. Though the turboramjets are using fuel from the rocket-stage too. It's not the first time I'm facing this problem, but circumventing this effect wasn't a problem with smaller, or more sane crafts. Though here it hurts greatly.

I have the following sub-ideal ideas to fix the issue:

- manually closing off and opening the rocket fuselages (too much hassle, has to be a better way)

- manually transfering fuel from the jet-stage before firing off the rocket engines (even more hassle, less time, minimal chance of keeping the CoM at the center)

- placing the wings on decouplers to stop crossfeed (not sure it would work, even more instability could be fatal, too tempting to just jettison them )

- fuel lines from jet tanks to central rocket tank... (wait, I just thought of that one. Is this the solution I'm looking for?)

It feels getting this to orbit would require a better solution. Got a better idea?

Craft file link - Beware! It's very stupid.

(forgot to remove the MechJeb module, though it's the only mod-part in there)

Edited July 28, 2015 by Evanitis

[xtoro]

Your best bets are to use decouplers along with struts to reinforce, or, manually lock the tanks. I really wish you could lock and unlock as an action group...

[I_Killed_Jeb]

fuel lines from jet tanks to central rocket tank

Can confirm this does not behave like the pre-1.0 days. The tanks still all drain

[GoSlash27]

Evanitis,

You got it. Fuel lines from jet tanks to rocket tanks.

Best,

-Slashy

[cantab]

Fuel lines from the LF tanks to the LFO tanks may suffice. The jets will draw fuel from all tanks, then the rockets will draw from the LF tanks first then the LFO tanks so will be able to access all the remaining fuel.

Use of parts that disallow crossfeed may work, but ups the part count.

[Sharpy]

If you reduce the number of LFO tanks (e.g. using Rockomax + quad-adapter) that reduces the number of tanks that need to be enabled/disabled too.

[ajburges]

I just do fuel transfer mid flight.

I find that 30-60 seconds after lighting anaerobic engines, my flight stabilizes at my desired heading. As long as the jets leave me with a minute plus burn time in fuel, I have plenty of time to transfer jet fuel. Since I always disable oxidizer flow on the front tank for aerodynamic stability for the early part of the burn, it's not like all fuel is immediately available to burn regardless.

The only space plane design of mine that does use the drag adding fuel lines uses the jet pods for (almost) all rocket fuel storage. I like the aesthetics of keeping jets to the same stack as intakes and keeping the rocket fuel in the same stack as the engines would have made the craft too long (the primary craft feature was 2.5 module long Mk2 cargo bay).

I am considering bumping it up to 3 modules (the nuclear tugs that are its capstone cargo barely fit), but I'm unsure of how that would affect design balance. I laugh because the craft was initially designed to lift scan-sats, but I realized that I could extend the design to handle tugs and reduce my fleet count. Since the proving flights it has become my go to lifter design.

Sadly, with RAPIERs just unlocked, it's probably time to build its successor. I don't think I'll find a good 6 node configuration to replace the 4 turbo, 2 spike engine array. I'll still try to niavely replace the turbos with RAPIERs first though.

Edited July 28, 2015 by ajburges

[Evanitis]

Rockomax + quad-adapter

Indeed, such helps but that's a career plane, just after a rushed unlocking of the turboramjet. Fuel-lines worked BTW, the silly plane got to orbit without touching the payload's fuel.

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I forgot to put batteries and some forward control authority on the return part, but it -almost- could land even without those. Backwards.