Hi, my name is Will Swisher. I'm seven years
old. I want to know how Rockets get
past our atmosphere.
My name is Jim Lattis, I'm the director of the UW Space Place.
Rockets that are launching things
into space, satellites let's say, into
space or space probes to go off
somewhere else in the solar system.
Do we have to get past the Earth's atmosphere?
But they don't have any trouble doing it
really the atmosphere is the biggest
problem. Rockets encounter most of the
resistance to their motion near the
Earth's surface, and the higher up they
get, the thinner the air gets, and so the
resistance gets lower so it actually
gets easier for a rocket engine that's
lifting some heavy weight into space, it
gets easier actually as it gets higher.
There is something that you commonly see
though that tells you that there's a lot
of work going on closer to the Earth's
surface than higher up and that is that
as the as a rocket typically burns up,
it's the fuel that's
actually propelling the rocket away
from the earth and it burns up the fuel,
so more and more basically the gas tank
gets emptier and emptier. Usually there
are two tanks and they're both largely
empty by the time you would get high
above the Earth's surface. And at that
point, the engine is doing more work just
to lift the empty gas tanks
and the engines then it is
to move the payload. And so rockets are
designed in stages so that there's what
they usually call a booster stage, or the
first stage, that is largely emptied and
then discarded before the payload
actually goes into orbit. And then
there's a second engine and fuel stage
the second stage or maybe even sometimes
a third stage depending on just what
they're doing, so it gets a little bit
complicated in part because of all
the work that the end that the rocket
engine has to do near the Earth's
surface, but actually gets easier as they
get higher rather than harder.
