Recovering upper stages - in orbit?

[sevenperforce]

18 minutes ago, Pand5461 said:

@sevenperforce, you are right, OMS circularization started about 30 minutes after MECO (according to Wikipedia). This basically means that MECO was almost at the perigee of a suborbital trajectory at around 120 km altitude.

There's a thread discussing the Shuttle guidance algorithm.

I looked at the equations - the guidance does not intrinsically rely on the coast between MECO and circularization. But a coast phase was explicitly specified, so that was what guidance algorithm should adapt the ascent trajectory to. I'm not sure what could happen if the algorithm was told to insert the whole thing into 200 km circular orbit. I think it could find a suitable pitch program, question is how much more fuel such trajectory would require (given the increased gravity losses because Shuttle would need to climb at a steeper angle to get to 200 km in basically the same time it climbed to 120 km in the real flights).

It wouldn't be at the perigee. At MECO, the Shuttle stack was climbing in a technically-complete orbit with a fairly high apogee and a perigee of about 0 km, plus or minus 15 km. OMS circularization happened close to apogee less than half an orbit later.

[kerbiloid]

According to wiki, max payload of Shuttle is 25 t (strange, I always had read about 29.5 t).
According to this, the heaviest real Shuttle payload ever is 22.7 t.
I.e. in any flight Shuttle was "underweighted" at least for 2.3 t.

If a typical fuel tank dry mass is, say, 8% of its total mass (for cryo) or less (for hypergolic, like for Shuttle's OMS), this means that an additional fueld tank could contain up to 2 t of fuel more.

According to this, Buran could carry additional fuel tanks in the cargo bay (## 9 and 12 o the picture)

Spoiler

So. dV = 3000_{hypergolic, vacuum} * ln((105_orbiter+27_{empty Big Orange Tank}+2.3_{Additional tank inside})/(105+27+2.3-2)) = 45 m/s.

So, with the lightest possible additional (and reusable) tank, Shuttle could put the Big Orange Tank into orbit, even not spending its "regular" fuel.

Edited September 29, 2017 by kerbiloid

[DerekL1963]

9 hours ago, kerbiloid said:

So, with the lightest possible additional (and reusable) tank, Shuttle could put the Big Orange Tank into orbit, even not spending its "regular" fuel.

Which still doesn't correct the basic problem - you've now spent the entire cost of a Shuttle launch to orbit what is a largely useless lump of metal.  To convert it into something only somewhat useful will require not only tens to hundreds of millions of dollars worth of development and assembly work preflight, but also a number (at least 2-3+) of additional (dedicated) Shuttle flights.  In the end, you don't gain much (if anything) over simply building modules that will fit in the cargo bay in the first place.

[DDE]

@kerbiloid, Shuttle's and Buran's plumbing in incompatible. The latter had an integrated kerolox thruster network. The former had separate bow and aft hypergol systems, so I'm not sure an internal bay tank is actually easy to implement.

[kerbiloid]

52 minutes ago, DDE said:

Shuttle's and Buran's plumbing in incompatible. The latter had an integrated kerolox thruster network.

I don't mean "use Buran tank in Shuttle", I mean "if Shutlle had an additional tank like Buran had".