On Wednesday, 19 December 2012 at 21:00:20 UTC, Walter Bright
wrote:
On 12/19/2012 2:05 AM, eles wrote:
Consider the US space shuttle design. It's probably the most
wrong-headed
engineering design ever, and it persisted because too many
billions of dollars
and careers were invested into it. Nobody could admit that it
was an extremely
inefficient and rather crazy design.
Hey, this is really OT, but I'm interested in. Why do you
consider it is such a
bad design? Because the shuttle is intended to be reentrant
and this is costly?
Some other issue?
Is about the design or about the entire idea?
It boils down to the overriding expense in spaceflight is
weight. There's the notion of "payload", which is the weight of
whatever does something useful in space - the whole point of
the mission.
Every bit of weight adds a great deal of more weight in terms
of cost to push it all into orbit.
To make the shuttle return and land, you've got wings, rudder,
landing gear, flight control system, basically a huge amount of
weight devoted to that. That weight subtracts from what you can
push up as payload. All of the lifting capability for that also
must be insanely reliable.
(And never mind needing things like a custom 747 to transport
it around because it's too big to go on the roads, all that
money spent trying to make a reusable heat shield, etc.)
Now consider the only thing that actually has to return are the
astronauts. And all they actually need to return is a
heatshield and a parachute - i.e. an Apollo capsule.
Thinking about it from basic principles, you need:
1. astronauts
2. payload
3. a way to get the astronauts back
So the idea then is to have two launches.
1. an insanely reliable rocket to push the astronauts up, and
nothing else
2. a less reliable (and hence cheap) heavy lift rocket to push
the payload up
The two launches dock in space, astronauts do their job,
astronauts return via their Apollo-style capsule.
Mission accomplished at far, far less cost.
The shuttle was originally intended to be a lot smaller and sit
atop the central booster, avoiding the issues that caused the
Columbia disaster. I believe that design may have been intended
to operate in the manner you suggest, however the CIA demanded
that the shuttle be made much larger to accommodate large
military satellites, distorting the design and making it a lot
less efficient.
