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Unless you are seeing what it would be like to launch on a
different planet or use a different liquid or gas, you wouldn't
normally need to change any of the parameters in this box.
However...
- Gamma: the compresibility of a gas depends upon
its molecules - whether the gas is made from single
atoms, for example with the noble gasses, He, Ne,
Ar etc or diatomic molecules such as O2, N2, Cl2 or
more complex molecules such as CH4, CO2, C2H6,
C3H6, C3H8 and so on.
The value is the ratio of heat capacities at constant
volume and constant pressure and is in effect how
springy it is.
Example values are:
- Air = 1.402;
- Ar = 1.662;
- He = 1.66;
- C2H6 = 1.26; and,
- CO2 = 1.304.
- Gas Density: the amount of gas in a given volume.
Counter-intuitively, a particular volume will contain
the same number of gas molecules regardless of
what that gas is. In this way, we can work out
density of a gas from its molecular weight (or
atomic weight in the case of a monatomic gas).
The magic volume is 22.4litres which contains
one mole of gas. Another way of looking at it is
that a cubic metre of gas at STP holds a little
over 44.6 moles of gas so if you were going to use
Xenon (cost is not an issue here...) - its atomic
weight is 131.29 and it is a noble gas so its density
would be 44.6 x131.29 = 5,956gm-3 or 5.956kgm-3.
Example values are:
- Air = 1.293;
- Ar = 1.784;
- He = 0.179;
- C2H4 = 1.260; and,
- CO2 = 1.977.
- Liquid Density: This is the density of the liquid at
the ambient temperature.
Example values are:
- Water = 998;
- Seawater = 1025;
- Hg = 13546;
- Olive Oil = 920,
- CCl4 = 1632; and,
- Br = 3100.
- Acceleration due to gravity: If you are thinking
about how this rocket would perform on the Moon,
Mars or some exoplanet, put the value in here.
Example values are:
- Sun = 274;
- Moon = 1.62;
- Mercury = 3.76;
- Venus = 8.77;
- Earth = 9.81;
- Mars = 3.80;
- Jupiter = 24.9;
- Saturn = 10.4;
- Uranus = 10.4;
- Neptune = 13.8; and,
- Pluto = 4.0.
- Atmospheric Pressure: Insert the barometric
pressure here. Note that this is the barometric
pressure where you are launching from and not
necessarily the pressure at lea level. If you are
launching at high altitude, this can become
relevant because it affects drag force on the
rocket of the atmospheric air of its surroundings.
- Density of Atmospheric Gas
Example values are:
- Air = 1.293;
- NH3 = 0.771;
- He = 0.179;
- H2 = 0.090;
- CH4 = 0.717;
- SO2 = 2.927; and,
- CO2 = 1.977.
Note that if the air pressure is substantially lower
or higher than that on Earth, still put the value at
STP into the density but put the atmospheric
pressure in the box above.
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