Answer 1:
Yes, but it requires some constants that I
don't have on me right now (you can find them in
the Handbook of Chemistry and Physics, if you can
get your hands on that. You can also probably find
them online if you know where to look). Step
1. Hydrogen and oxygen combine to make water
and release energy. I don't know how much energy
this is; this is the first thing you will need to
look up. The ratio is2 moles hydrogen (2 grams) to
one mole (16 grams) oxygen will make one mole (18
grams) of water vapor. You will be adding
hydrogen and oxygen together at a certain rate,
which is determined by the design of the rocket.
So, you can pick whatever rate you want based on
how fast you want your rocket to burn through its
fuel. DON'T assume that you can get oxygen
from the air!Oxygen is in the air, but for a
rocket engine you will need it faster than you can
get it in the air. Step 2. The water
vapor created by burning the two gasses will be
very hot, and will exert a pressure on its
surroundings, including the engines of the rocket.
The amount of pressure that it exerts will depend
on the temperature. Use the following formula:
Tnew = Told + E/k
Tnew is the
temperature of your water vapor Told is the
temperature of the oxygen and hydrogen before you
burn it (this will be cold, probably) E is the
energy released from the burning (what you just
looked up in step 1) k is the heat capacity of
water VAPOR (NOT liquid water!). You need to look
this up also. Step 3. This pressure is
what will provide the rocket's thrust. You can
calculate the pressure with the following
formula: PV = nRT
P = pressure V =
volume of the chamber (again, you decide this as
part of designing your rocket) n = moles of
water vapor R = universal ideal gas constant
(look this up in the handbook as well) T =
temperature (in Kelvin) that you just
calculated. You want P.
Step 4.
Pressure is force per unit area, so what you need
nowis the area of your engine where you are
burning your fuel and expelling the gas. You want
only the area of the roof of the burning chamber,
however, so this usually means the area of the
exhaust ports on the underside of your
rocket. F = P*A
Note: expelling the
gas will empty the chamber, so you will need to
add more fuel. As a result, what you probably want
is the amount of impulse, which is force over time
that you are generating by expelling the gas. PV =
(2/3)NKE is a good equation to use, N is the
number of atoms and KE the kinetic energy you are
getting. Step 5. You now want the
acceleration generated by your engine, which
depends on the mass of your rocket: F =
ma
This is how rapidly your rocket will
move. Remember, if you are trying to launch your
rocket up, you will have to counteract gravity.
The acceleration due to gravity is 9.81
m/s^{2}, so in order to get anywhere, you
need more than that. The Space Shuttle, I
think,has a total acceleration of about 13
m/s^{2}, which means that it is
accelerating at 3 m/s^{2} relative to the
Earth as it leaves the launch pad, because of
gravity.
