Launch Costs

On 30/05/06, Robert wrote:
> if the odds of it happening on any particular flight is on in 10000,
> by the time youve had 10000 flights, the odds are it will happen
> once. as long as there is one launch every 3 months, it will take a
> long time to launch 10000 times. on the other hand if its done on
> daily to weekly basis, it becomes a much more likely event.

No, for several reasons:

a) 1 in 10,000 is an appallingly large risk- no launch vehicle would
ever be allowed to launch with a 1 in 10,000 risk of hitting a densely
populated area. IRC 1 in a million is the chance of *anyone* on the
ground dying you need to hit before they'll sign off on the launch.
You *do* need permission to launch- it's called a launch license.

b) the chances of failure go down over time- the first space shuttle
had a 80% chance of success. The current space shuttle has a 98%
chance of success. That's after 200 flights. That's because they have
accidents, find the bug in the manufacture, operations or design,
repair it, and the reliability goes up.

> first thing is that your assuming that it only occurs after the ship
> reaches mach three. it is more likely that it will occur before it is
> even moving 100 miles an hour.

Duh huh. Then it isn't going very fast, and has gone very far, so
won't fall far from the launch point when you turn off the engines or
blow up the vehicle.

> it will then accelerate to mach three,
> giving it somewhat more stability, but by then its already off course.

Lessee. Rockets have a takeoff acceleration of between 1.5 and 2g.
Mach 3 = 340*3 = 1020m/s.

2g = 20m/s^2

Acceleration time to mach 3 = 1020/20 = 51seconds

Sooo. You're saying that something has gone drastically wrong with the
rocket (a 1 in a million failure), AND the range safety guy stands
there watching for 51 seconds with his thumb up his ass, in the middle
of a launch AND it's heading for a city. At mach 3. AND all this when
the vehicle isn't designed to do mach 3 in the atmosphere. And mach 3
isn't very fast, a vehicle can't go 100 miles at mach 3 even ignoring
wind drag.

It just isn't credible.

> if it nosed into the wrong direction just after launch it could
> easily reach half way to california from floida and still have enough
> fuel for that kind of explosive. how many cities do you think it
> would have passed.

I've simulated launch vehicles on computers. 99.9% of all trajectories
go hardly any distance- the atmosphere is incredibly efficient at
burning off fuel, at high speed. It's really, really difficult to get
a vehicle to orbit, and every bit as difficult to hit a city, and it's
made even more difficult because they design the vehicle not to do
that.

> i lost my wife due to a c 130 having multiple control system failure.

I'm very sorry to hear that.

> dont tell me it does not happen.

It happens.

The question is what the chances are of a rocket taking out a city.
The chances are very, very, very small indeed. The point is that the
regulations all start from the position that 'we don't care whether
you reach orbit, but you mustn't kill uninvolved people on the
ground'; and the regulations are applied that way.

--
-Ian Woollard

"Gravity is just a theory. We shouldn't be teaching it to children as
if were fact."
"The NSA would like to remind everyone to call their mothers this
Sunday. They need to calibrate their system."