Smells Like Teen Spirit

Ryan Z wrote:

>I don't quite follow how LEO is the key. If I'm
>launching beyond LEO, I don't even stop in LEO. I
>bypass it totally. If I want to goto the Moon, I try
>to boost into a lunar transfer orbit directly instead
>of LEO.
>
Good points. However, note that Apollo staged in LEO, before boosting to
the moon. The difference in delta-v was only about 100m/s as I recall,
and they preferred to check stuff out before doing the burn for the moon.

There are a number of other disadvantages of launching straight to
escape velocity:

a) your upper stage suddenly isn't reusable, because it isn't coming
back any time soon
b) if a stage isn't reusable then it becomes more expensive by a factor
of perhaps 10x
c) your upper stage is likely to be heavier than it needs to be, because
space-only stages only need smaller engines; whereas upper stages need
big ones because they are fighting gravity, this add to the dry mass and
increases the fuel needed
d) space taxi concepts where you launch only the fuel to LEO and not the
engines are more efficient
e) there's often problems with Van Allen belts- LEO is below the worst
of the Van Allen belts

> One of the major problem with the shuttle in
>fact is that it is stuck in LEO. What good is shoving
>things up 100 km in space when I really want to be
>23k+ km in space.
>
The major problem with the Shuttle is it is too expensive; that means
you can't use it to launch fuel.

>In fact, launching stuff into LEO just requires my
>spacecraft to waste precious lbs in fuel and
>propulsion systems to get it to the real orbit I want
>it to be in. A great example of how much mass is
>wasted in launching too low is the Cosmic Background
>Explorer. It was originally slated to be launched
>from the Shuttle in the late 80s into a polar orbit at
>900 km (i forgt the inclination). However, after the
>challenger accident it got switched to a delta 2
>launcher. Due to this it was able to reduce its mass
>by 50% by removing the fuel and propulsion systems
>neeed to it from the shuttle's orbit (about 100 km) to
>its designed orbit!
>
Delta-2 is a GEO sat launcher. Geosats are 3 stages, so this probe was
able to use the third stage to boost it up and could reduce the fuel in
it's own tank. The Shuttle is sort of a 2 stage design really, so the
probe itself becomes the third stage.

The rule of thumb is (1-)2 stages = LEO 3 stages = GEO/Escape

>Ryan Z
>

--
-Ian

Motto: "You're Not Authorized to Know Our Motto."
So, like, how many lives DOES Shroedinger's cat have anyway?