Rocket fuel question
Anthony Maw
For instance I have heard that amonium perchlorate is a common solid rocket
fuel. What other types are there?
Also I have often wondered why the Saturn V rocket booster used kerosene and
LOX in it's first stage but LH and LOX in the second ?
Anybody have answers ?
George Herbert
Anthony Maw <am...@direct.ca> wrote:
>What factors influence the choice of both solid and liquid rocket fuels ???
Performance, cost, density, handling safety/problems.
>For instance I have heard that amonium perchlorate is a common solid rocket
>fuel. What other types are there?
Oxidizer. Not fuel. For professional solids, it's basically either
perchlorate plus plastic binder/fuel plus metal fuel, or double base
(nitroglycerine/nitrocellulose). Some minor use of ammonium nitrate
as oxidizer (burns too slowly for most uses, though). Kids toy rockets
use black powder pellets.
>Also I have often wondered why the Saturn V rocket booster used kerosene and
>LOX in it's first stage but LH and LOX in the second ?
>Anybody have answers ?
A concept called density impulse, and another concept called specific
impulse, respectively.
Specific impulse is the fuel efficiency rating for rocket fuels,
measured in one of two ways: the exhaust velocity (in meters per
second or rarely feet per second) abbreviated Ve, or true specific impulse,
which is the number of seconds one mass unit (lb) of propellants
will burn for to produce the same mass unit's force equivalent
(lb force) worth of thrust, abbreviated Isp. They are directly
related: Isp * g = Ve (g is the acelleration of gravity, 9.8 m/s
or 32 ft/sec). The higher the better, obviously.
For lower stage rockets, though, density impulse can be more important.
Density impulse is specific impulse multiplied by the average density
of the propellant. This takes into account how much propellant you
can stuff into a given sized (and weight) tank. The density of
kerosene and LOX together is around 0.9, with Isp around 270
at sea level. (side note: Isp varies from engine type to engine type
and with altitude, as well as just the fuels; I am using rough average
numbers here). The density of liquid hydrogen plus LOX is more like 0.2
with Isp around 380 at sea level. Depending on design details and the
rest of the configuration, a particular concept may do better with
a first stage using the denser but "lower performance" LOX+kerosene
than with hydrogen. Upper stages almost always work out favoring
more Isp than density impulse, for efficient rocket designs,
but not always.
-george william herbert
gher...@crl.com
murray...@webmail.bellsouth.net
"Anthony Maw" <am...@direct.ca> wrote:
> What factors influence the choice of both solid and liquid rocket fuels ???
>
> fuel. What other types are there?
>
> LOX in it's first stage but LH and LOX in the second ?
>
> Anybody have answers ?
>
>
Cost vs Control & higher specific impulse
solids have a lower cost
liquids have higher cost, higher overhead (plumbing, etc.)
and higher specific impulse/wt. (at least in the
case of H2/O2 systems.
kerosine is cheaper the LH, and vastly easier to deal with
since it doesn't require high pressure, low temp considerations.
LH/LOX systems on the other hand have a higher thrust to weight ratio
compared with other liquid or solid fuels.
Obviously, liquid fuel systems have an advantage of being able to
be controlled or turned off. Solids are on until the fuel runs out
or the rocket blows up.
Solid fuels - well, the little Estes rockets I've shot use a type
of black powder from what I've heard. There are large numbers of
rocket fuel fuels/formulations.
Apologies for inaccuracies, fallacies, or outright lies.
Regards,
Glenn
--
"Understanding is a three-edged sword."
radagast @ mindspring . com
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Dirk Bruere
>
> numbers here). The density of liquid hydrogen plus LOX is more like 0.2
> with Isp around 380 at sea level. Depending on design details and the
> rest of the configuration, a particular concept may do better with
> a first stage using the denser but "lower performance" LOX+kerosene
> than with hydrogen. Upper stages almost always work out favoring
> more Isp than density impulse, for efficient rocket designs,
> but not always.
I assume that higher density is better in the first stage as it makes
for a smaller cross-section for flight through the bulk of the
atmosphere, and the second stage is not only smaller mass (but roughly
same cross-section as first), but flies exo atmospheric.
Dirk
person_b
>
> Cost vs Control & higher specific impulse
>
> solids have a lower cost
>
> liquids have higher cost, higher overhead (plumbing, etc.)
> and higher specific impulse/wt. (at least in the
> case of H2/O2 systems.
>
> kerosine is cheaper the LH, and vastly easier to deal with
> since it doesn't require high pressure, low temp considerations.
>
> LH/LOX systems on the other hand have a higher thrust to weight ratio
> compared with other liquid or solid fuels.
>
> Obviously, liquid fuel systems have an advantage of being able to
> be controlled or turned off. Solids are on until the fuel runs out
> or the rocket blows up.
>
> Solid fuels - well, the little Estes rockets I've shot use a type
> of black powder from what I've heard. There are large numbers of
> rocket fuel fuels/formulations.
>
> Apologies for inaccuracies, fallacies, or outright lies.
>
> Regards,
> Glenn
> --
> "Understanding is a three-edged sword."
> radagast @ mindspring . com
Glenn,
If I may ask, I have a question for you.
What would you recommend as the propellant for a rocket launcher?
What do they typically use as propellant and what would be an improvised
solution?
Thanks.
me
If I may ask, I have a question for you.
What would you recommend as the propellant for a rocket launcher?
What do they typically use as propellant and what would be an improvised
solution?
Thanks.
> I'm not the one to answer this, but since nobody else has...
murray...@webmail.bellsouth.net
me <m...@hotmail.com> wrote:
> Glenn,
>
> If I may ask, I have a question for you.
>
> What would you recommend as the propellant for a rocket launcher?
>
> What do they typically use as propellant and what would be an improvised
> solution?
>
> Thanks.
>
Honesty, I wouldn't use a propellant for a rocket launcher. Now using
it for a rocket would be a different subject.
All humor aside, I'm not the one to talk to. I have some (extremely limited)
book knowledge of propellents, primarily from a background in chemistry.
This kind of knowledge, minus practical experience, can be highly dangerous
in a field where things burn fast and occasionally blow up.
Good luck and be careful,
Glenn
> > I'm not the one to answer this, but since nobody else has...
> >
> > Cost vs Control & higher specific impulse
> >
> > solids have a lower cost
> >
> > liquids have higher cost, higher overhead (plumbing, etc.)
> > and higher specific impulse/wt. (at least in the
> > case of H2/O2 systems.
> >
> > kerosine is cheaper the LH, and vastly easier to deal with
> > since it doesn't require high pressure, low temp considerations.
> >
> > LH/LOX systems on the other hand have a higher thrust to weight ratio
> > compared with other liquid or solid fuels.
> >
> > Obviously, liquid fuel systems have an advantage of being able to
> > be controlled or turned off. Solids are on until the fuel runs out
> > or the rocket blows up.
> >
> > Solid fuels - well, the little Estes rockets I've shot use a type
> > of black powder from what I've heard. There are large numbers of
> > rocket fuel fuels/formulations.
> >
> > Apologies for inaccuracies, fallacies, or outright lies.
> >
> > Regards,
> > Glenn
>
--
"Understanding is a three-edged sword."
radagast @ mindspring . com
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