From: Bruce Dunn <bruce_dunn@mindlink.bc.ca>
Newsgroups: sci.space.tech
Subject: Re: chilled fuel (was: Re: Alternative means of achieving orbit)
Date: Tue, 30 Apr 1996 08:19:53 -0700

Jim Glass wrote:


> For RP-1, I have only an ESTIMATE based on the work of Dr. Joeseph
> Scharrer:
> 
> RP-1 at 175.68 R   density = 58.77 lb/ft3
> RP-1 at 70F        density = 50.28 lb/ft3


In international units, this puts RP-1 at:

98  K:  941 kg/m^3
294 K:  805 kg/m^3

Hydrocarbons however vary all over the place:  the density of "kerosene"
depends on exactly what the "kerosene" is.

The book "Rocket Propellants" by S.F. Sarner lists for density at 15 C:

JP-1:  810 kg/m^3  (narrow cut kerosene, to expensive to make, abandoned)
JP-2:  764 kg/m^3  (experimental, not now used)
JP-3:  760 kg/m^3  (wide cut, wide boiling, volatile, not now used)
JP-4:  773 kg/m^3  (current jet kerosene)
JP-5:  827 kg/m^3  (narrow cut, low volatility similar to RP-1)
JP-6:  817 kg/m^3  (similar to JP-5 but lower freezing point)
RP-1:  806 kg/m^3  (specified for 1950+ US rockets)
T-1 :  825 kg/m^3  (Russian jet fuel similar to JP-5)

The density of RP-1 with temperature isn't listed, but that of RP-1 is:

50 C :  802
20 C :  824
0  C :  838
-20 C:  852
-40 C:  867

However, the viscosity of the kerosene rapidly increases as it is cooled,
and at some point will get too low for effective use.  It isn't clear
at what point this is, but Sarner doesn't give densities at temperatures
less than -40 C, and JP-6 seems to have been developed because even for
aircraft use they were having trouble with JP-5 freezing.  Certainly,
at LOX temperatures you don't have a liquid, but will have a solid
probably somewhat resembling chilled paraffin wax.

From: Bruce Dunn <bruce_dunn@mindlink.bc.ca>
Newsgroups: sci.space.tech
Subject: Re: chilled fuel (was: Re: Alternative means of achieving orbit)
Date: Tue, 30 Apr 1996 09:11:55 -0700

Oops!  I wrote:

>The density of RP-1 with temperature isn't listed, but that of RP-1 is:

I meant to write:

The density of RP-1 with temperature isn't listed, but that of JP-5 is:
                                                               ^^^^

50 C :  802
20 C :  824
0  C :  838
-20 C:  852
-40 C:  867

In practice, it is probably difficult to get hydrocarbon densities above
about 850 kg/m^3 with any sort of material with an empirical formula of
about ...CH2...  Those hydrocarbons such as ethane, propane, butane etc.
which can be chilled to really low temperatures aren't dense to start
with, and don't generally get to a density of even 800 kg/m^3 when they
start freezing.  Some aromatic hydrocarbons have higher densities (for
example benzene at 900 kg/m^3 at 0 C) but don't work well as fuels as
their molecular formulas are deficient in hydrogen (benzene is C6H6).

From: Henry Spencer <henry@zoo.toronto.edu>
Newsgroups: sci.space.tech
Subject: Re: chilled fuel (was: Re: Alternative means of achieving orbit)
Date: Wed, 1 May 1996 16:28:41 GMT

In article <1996Apr26.143107.25929@nb.rockwell.com> glass@mrbig.rockwell.com (Jim Glass) writes:
>For RP-1, I have only an ESTIMATE based on the work of Dr. Joeseph
>Scharrer:
>
>RP-1 at 175.68 R   density = 58.77 lb/ft3

RP-1 freezes at about 225K (about 405R).
-- 
Americans proved to be more bureaucratic           |       Henry Spencer
than I ever thought.  --Valery Ryumin, RKK Energia |   henry@zoo.toronto.edu

Subject: Re: chilled fuel (was: Re: Alternative means of achieving orbit)
From: Henry Spencer <henry@zoo.toronto.edu> 
Date: Apr 24 1996
Newsgroups: sci.space.tech

In article <viybnoooo2.fsf@im.lcs.mit.edu> Daniel Risacher <magnus@im.lcs.mit.edu> writes:
>...I'm most interested in the density of RP-1 at LOX temperatures.

At LOX temperatures, RP-1 is a rock-hard solid.  Its density is of purely
academic interest unless you have some very unusual engine concept...

If you want hydrocarbons that are still liquid at LOX temperatures, you
have to resort to propane or something even lighter.  Propane is still
liquid there, although only just.  Methane is still a gas, although again
only just.  Those are the two popular choices for cryogenic hydrocarbons. 
-- 
Americans proved to be more bureaucratic           |       Henry Spencer
than I ever thought.  --Valery Ryumin, RKK Energia |   henry@zoo.toronto.edu

Subject: Re: chilled fuel (was: Re: Alternative means of achieving orbit)
From: Henry Spencer <henry@zoo.toronto.edu> 
Date: Apr 22 1996
Newsgroups: sci.space.tech

In article <31722C05.6502@london.virgin.net> mattb@london.virgin.net writes:
>> Greater density, cramming more propellant into tanks of a given mass.  Also
>> a bit of improvement in cooling effectiveness.
>
>Anyone know of any other applications which use chilled fuel? And just 
>_HOW_ chilled? How cold do you have to get it to make a significant 
>difference? What kind of density changes are we talking here?

Typically the density changes are small -- but still potentially useful --
unless you cool to cryogenic temperatures, which is workable for only a
few fuels.  (Propane is the canonical example of a fuel that benefits,
going from 0.59 at its boiling point to 0.72 at LOX temperatures.)

Maximum packaging density seems to have been a major objective for Zenit,
so it's not out of character that they opted for chilled fuel.  (Just
*why* it was a major objective is less clear.  The usual reason for such a
decision is that the thing started out as a missile and had to fit within
existing silos/submarines/whatever, but Zenit seems too big for that.)

>I've also heard tell that very long-range aircraft (those going for a 
>record, usually...) are sometimes topped up at runway's end and chill the 
>fuel.

Chilled fuel is a fairly standard feature of aircraft record attempts.
For example, it featured in the successful effort NACA made to push the
Douglas Skyrocket -- basically a Mach 1.8 aircraft -- to Mach 2.
-- 
Americans proved to be more bureaucratic           |       Henry Spencer
than I ever thought.  --Valery Ryumin, RKK Energia |   henry@zoo.toronto.edu