On 3/2/2014 9:55 AM, Anthony Frost wrote:
In message
David Spain wrote:

2) Simplification of the recovery effort of a multi-booster
configuration such as the Falcon-9 Heavy. Instead of having to manage
the recovery of three separate boosters, you only need deploy landing
legs on the three and have a single point-of-control for the active
recovery.

What are you proposing to use to hold the stages together, very long
bits of string? Consider why this wouldn't have worked to recover the
shuttle ET and SRBs as a single package...


I'm answering your comment and question in reverse order.

I consider the SRB/ET-Shuttle as a TSTO system with the ET as part of
the 2nd stage not the first stage since it was never designed to be
recoverable. A very different system than an F9HR with recovery
capability on all three boosters. But done so independently. Thus
if/when F9HR becomes a reality there will be 3 separate boosters to
control on return rather than one.

No in this scenario the boosters don't separate at all, they go up as
one and come down as one. Yes you loose the advantage of cross-feed
propellant or engine throttle down on the core booster since at no time
does it fly standalone. So there is that reduction in performance as
well. I could speculate you *might* be able to make up that difference
by stretching the boosters a bit, but barring that you loose the
performance gain of a throttle down throttle up core booster OR it puts
significant additional burden on the 2nd stage. Perhaps too much of one?

From an engineering perspective it seems far easier (read less costly)
to eventually just build out a recoverable single BFR rather than deal
with the added complexity of recovering the multiple boosters of a
smaller rocket bundled together. I think that was the gist of the debate
in the other forum. This trans-stage option might have been one solution
to that problem. Albeit maybe not a very good solution.

But I am most interested in learning if this trans-stage option was
given any serious consideration in the past.

I guess the snide remark is that NO-ONE was giving rocket recovery any
serious consideration in the past. Folks just got too comfy with
governments footing the bill for what was nearly a monopoly market with
a single payer customer, with the occasional well-heeled commercial
client thrown in.

Dave