Re: Space Shuttle Grounding....depressing....

Andre Lieven wrote:
Andrew Swallow (am.swallow@xxxxxxxxxxxxxxx) writes: 
[snip]

Or give the orbiter a fourth engine and a bigger fuel tank. 


Given that the SRBs each put out 3,000,000 pounds of thrust, you'd
need to add 6,000,000 pounds of thrust in eliminating the SRBs.

As the SSMEs only put out around 400,000 pounds of thrust each,
you're going to need not one more, but about fifteen of them. Plus,
the starter three.


These values suggest that the underlying problem is elsewhere.

At launch the assembly is giving off
2 * 3,000,000 + 3 * 400,000 = 7,200,000 pounds of thrust

So the three SSMEs plus the fuel tank are equal to less than
half a SRB.

Use three SRBs at launch and the SSMEs do not need to be
fired.  If the SSMEs do not need firing then they do not
need to be at the bottom of the assembly, permitting the
SRBs to be place underneath - like in a traditional rocket.

A set of 3 SRBs will not get you into orbit but two sets
will get you very high and fast.

During launch burns have to be very powerful otherwise you
fall back to the ground.  In orbit a spaceship can have a
weaker burn that lasts 3 times as long.

The orbiter needs an engine to manoeuvre in space.  I
suspect that it does not need 3 engines, so 2 of them
are an unnecessary weight.

When the kludge is unwound the resulting design is very
close to that of the traditional 3 stage rocket.   The
first stage can save weight by taking its oxygen from
the air.

Andrew Swallow

.

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