Rocket Engine Specific Impulse Program
Specific Impulse (Isp) is a measure of the “fuel efficiency” of a rocket. The necessary thermodynamic calculations for Isp are performed by a package of text based programs and files which run on MS-DOS or Windows based personal computers.
Download Isp Program isp2001.zip (229 KB)
The download package includes the following help file which I wrote for users.
README
file for Air Force Specific Impulse Program
For
easiest reading, display this text file using a fixed space font such as
Courier, or use the Notepad program on any Windows computer.
This
README file was written by Dr. Bruce Dunn, Vancouver, Canada. This version is dated November 2001, and is
a modification of a README file originally written in 1993. This file is designed to aid others in the
use of the program. I am ***not*** the
author of the program. My contact
information as of the date of writing of this file is:
Dr.
Bruce Dunn
Dunn
Engineering
2750 W.
12th Ave.
Vancouver,
B.C.
Canada
V6K 2P6
(604)-837-8707
*****************************************************************
The
Isp.exe code is the "Air Force Chemical Equilibrium Specific Impulse
Code". A utility called
"Inp.exe" accompanies the program.
It was written by Curtis Selph to aid in the preparation of data for the
running of the program. The program
package was originally obtained through Mitchell Burnside-Clapp, then of the US
Air Force. To my knowledge, no source
code is available for the program.
The
files in this package comprise a program for calculating the specific impulse
of rocket engines. The program assumes
that users have basic textbook knowledge of the meanings of various terms
involved in the characterization of the performance of rockets.
The
files required for the program to run are as follows:
allprop.dat data on rocket propellants (can be
expanded and
modified by users)
inp.exe a utility program which is used to
specify the
propellants, chamber pressure etc.
hlp.doc help files for inp.exe, read when
inp.exe is executed
isp.exe the program which actually
calculates the Isp
thergg.dat a file containing needed data
therii.dat a file containing needed data
therss.dat a file containing needed data
not
needed for execution are:
readme.txt this help file
the
first time isp.exe is run, it will create two additional files:
output.dat the output from the program, readable
with a text editor
tabout.dat a binary file containing (presumably)
information on the
arrangement of data in the
output file
each
time the isp.exe is run, output.dat and tabout.dat are overwritten by new
versions
To
calculate the Isp of a rocket engine, proceed as follows:
1) Run
inp.exe. You will get a page of
instructions, followed by a series of menus which allow you to enter data on
the propellants to be burned in your engine, their proportions (either pre-determined
by you, or via instructions for the "optimizer" which systematically
tries different propellant proportions),
the chamber pressure, and the expansion ratio(s) or exhaust pressure(s)
which you wish to have the Isp calculated for.
When you specify propellants, their characteristics (density, MW, heat
of formation etc.) are looked up from the data stored in the propellant library
(allprop.dat). Other menu items allow
you to change how the program does the calculations (you can ask for
"frozen flow" rather than "shifting equilibrium"
calculations), and what the output looks like [it is suggested that initially
these be left at their default values].
Once all the information is determined, you select the menu item which
allows you to exit inp.exe. The program
will then save the relevant information in a file, using a file name provided
by you.
Hint: to specify kerosene as a fuel, locate the
propellant data by the name "RP-1"
Hint: the term "NBP" indicates that the
propellant is at its normal boiling point
Hint: for some propellants, there may be two
entrys, for different propellant temperatures.
After locating the propellant desired, answer No when the program asks
you if this is the propellant that you mean - other matches to the propellant selection
criteria that you give are then displayed
Hint: only 100% H2O2 is available as a
propellant. To perform calculations for
an engine such as one burning kerosene with 90% peroxide, select peroxide, H2O,
and kerosene as propellants. Set the
mass of peroxide at 0.9, the mass of water at 0.1, and vary the mass of
kerosene to change the mixture ratio.
For example, 0.9 peroxide, 0.1 water, 0.15 kerosene is an oxidizer/fuel
ratio of 1/0.15, or 6.66.
2) Run
isp.exe. The program will prompt you
for the name of the file which you created in step 1. Once this is given, isp.exe will carry out the calculations. The results will flash on the screen too
quickly to been seen. Don't panic, the
program also writes the information to the file output.dat.
3) Read
the file output.dat with your favorite word processor or text editor. The output tables are created with spaces,
not tabs. Therefore, to make sense of
the tabulated data, it is essential to use a fixed width font. The output table can also sometimes use long
line lengths, and when using a word processor to view the file, individual data
lines will wrap onto new lines, destroying the formatting of the tables. In this case, either select a smaller font
or a larger paper size such as legal paper in landscape mode, to prevent line
wrapping.
4) If
you are not happy with the results in the tables, you don't need to create a
new input file from scratch. Run
inp.exe again and select the menu item indicating that you wish to create a new
input file. The program will then give
you the option of basing the file on a previous one. Once the input file has been modified, it can be saved under the
old name or under a new name.
5) You
can add your own propellants to the propellant library, or modify the properties
of a listed propellant using menu items in input.exe. Since there is a possibility of someone accidentally corrupting
data in the propellant library, for critical work it is suggested that the
thermodynamic data, propellant density etc. for each propellant used be checked
against an independent source (the data is displayed at the time a propellant
is selected).
The
following points should be noted:
The
program is not written to use SI units, and uses a grab-bag of American, pre-SI
metric, and SI units. For example,
energy is in calories rather than joules, temperature is Kelvin, and pressures
are in psi. Investigators who want to
use chamber pressures in MPa, must multiply by 145 to get an equivalent value
in psi in order to enter the chamber pressure into the program (i.e. a 5 MPa
chamber pressure must be entered as 745 psi in the program). If you want to enter thermodynamic data for
propellants, remember that 1 calorie equals 4.187 joules.
The
program calculates the conditions of the chamber and throat, then calculates
the conditions and Isp for any specified expansion conditions. Expansion conditions may be given either by
specifying the exit pressure, or by specifying the nozzle area expansion. You can specify more than one expansion condition; for example in a single run you can
calculate the Isp for exit pressures of 30 and 15 psi, and area expansion
ratios of 4, 5 and 6.
The
program calculates two Isp values:
"Isp (optimum)" [which is listed as just "Isp" in
the output tables] and "Isp (vacuum)". Isp (optimum) is the Isp for an engine in which the gas pressure
at the plane of the exhaust is exactly equal to the ambient atmospheric
pressure. If you ask to have Isp
calculated for an exit pressure of 14.7 psi (sea level atmospheric pressure),
then the calculation will determine what nozzle size is necessary to expand the
gas to 14.7 psi. The output table will
give "Isp" which is the Isp for that engine expanding the gas to 14.7
psi, and exhausting the gas against an outside atmospheric pressure of 14.7
psi. The output table will also give
"Isp (vacuum)" which is the Isp that the same engine would have if
operating in a vacuum.
Except
for the special case of engines operating in a vacuum, the program does not
directly calculate the performance of under or over expanded engines (where the
calculated pressure at the exhaust plane is lower or higher than ambient
atmospheric pressure). There is
sufficient information however in the output tables to be able to estimate Isp
for such conditions (see below).
The
output of the program is the traditional rocket engineer's "Isp", or
specific impulse. The units of Isp are
seconds, and due to the way that a pound of force and a pound of mass are defined
in the US. measurement system, the unit includes the reciprocal of the
acceleration of gravity at the earth's surface. To convert Isp into SI units, multiply Isp by the standard
acceleration of gravity, 9.807 m/s^2, to get exhaust velocity in m/s. An Isp of 300 s thus becomes 300*9.807 =
2942 m/s. Through unit conversion, the
same 2942 m/s is also equal to 2942 Ns/kg. In other words, 1 kilogram of
propellant will give a thrust of 2940 Newtons for 1 second, or 1 Newton for
2940 seconds etc.
The
"theoretical Isp" values given in many textbooks are calculated for a
single standard condition, namely 1000 psi chamber pressure and optimum
expansion to atmospheric pressure (14.7 psi).
Tables of such calculations often state the mixture ratio - if not stated,
it can be assumed to be optimized to give the highest Isp. If it is desired to compare the results of
calculations done with the program against those in textbooks, the program must
use the standard conditions listed above.
The
mixture ratio generating the highest Isp for a given propellant combination is
not necessarily the stochiometric mixture ratio. Often, the highest Isp is generated under fuel rich conditions,
which typically result in some unburned hydrogen in the exhaust. Even then, not all real-world engines are
run at the optimum mixture ratio. A
non-optimum ratio may be chosen to lower the chamber temperature to aid cooling
of the combustion chamber and throat, or to minimize the use of bulky propellants
such as liquid hydrogen.
By default,
the program calculates a theoretical Isp by the "shifting
equilibrium" method, which assumes that the exhaust species are constantly
in chemical equilibrium as they expand.
This type of calculation is conventional, and gives the type of values
typically quoted in textbooks. However,
such calculations are overly optimistic, in that in practical engines the
exhaust process is so quick that some energy releasing processes in the exhaust
aren't fast enough, and the actual exhaust products are not in chemical
equilibrium. A better estimation of
real world performance is obtained by asking the program to do a "frozen
at throat" calculation in which the chemical species are assumed to be in
chemical equilibrium up to the throat of the engine, but then are assumed to be
"frozen" (no further chemical reactions). This mimics behavior in
real world engines - at the throat, there is a sharp drop in temperature which
slows chemical reactions, and a sharp increase in the velocity of the gas,
which reduces residence time (the quicker the gas is expelled from the engine,
the less time there is for chemical reactions to go to completion).
To
perform a "frozen at throat" calculation, enter the propellant data,
the chamber pressure, and the expansion conditions. Note that for this type of calculation, you must give expansion
conditions as an area ratio, not as an exit pressure. Next, select menu item 4 (Application Options). Then select menu item 3 (Include Frozen
Flows). Type "Y" at the
question "Do you want frozen flow calculations?", then select
"throat" as the station where you wish the flow to be frozen. As a quick check that you have correctly
selected a "frozen at throat" calculation, look at the chemical
species list in the output table. If
you have set things up correctly, the proportions of different species will
change from the chamber to the throat, but won't change from the throat to the
nozzle exit.
The
calculation process ignores a variety of losses occurring in real world engines
such as incomplete combustion, non-uniform mixture ratio across the injector,
nozzle friction and the use of propellants for purposes other than thrust (such
as film cooling, powering turbopumps and providing tank ullage gas).
In
practice, the real world Isp of most engines is slightly lower than calculated
values of "frozen at throat" Isp.
The following table compares the theoretical results of calculations for
a number of Rocketdyne engines, with performance data taken from some older
Rocketdyne specification sheets (NB. engines are modified from time to time -
do not compare the specifications of these engines with those of current
versions of the engines).
Engine Condition MR Chamber E Real
Calc. Fraction
O/F psi
Isp Isp
F1 sea level 2.27 982
16 265 281.5
0.941
RS-27 sea level 2.24 702 8 262.5
279.3 0.939
H1 sea level 2.23 700
8 263 279.1 0.942
MA5-boost
sea level 2.25 639 8
259.1 276.0 0.939
MA5-sust.
sea level 2.27 735 25
220.4 239.5 0.920
J2 vacuum 5.5 763 27.5 425 434.4 0.978
SSME vacuum 6 3260 77.5 453.5 452.9 1.004
MR = oxidizer/fuel mixture ratio
Chamber = chamber pressure in psi
E = nozzle area expansion ratio
Real
Isp = Isp from Rocketdyne data sheet
Calc.
Isp = Isp using "frozen at throat" assumptions, with corrections
for non-optimum expansion, as
described below
The F1,
RS-27 and H1 engines are LOX/kerosene engines designed as first stage engines
for boosters. All are slightly
overexpanded at sea level (the F1 has an exit pressure of about 6.8 psi, and
the RS-27 and H1 about 12.3 psi). The
MA5 engine uses the same propellants, but is a three chamber engine, with two
boost chambers and nozzles designed for sea level operation, and 1 sustainer
chamber and nozzle designed for high altitude efficiency. At sea level, the booster engines are
slightly overexpanded (exit pressure 11.2 psi) while the sustainer is very
badly overexpanded, to a point where there is probably flow separation in the
nozzle (exit pressure 2.8 psi). All the
kerosene engines have a real world Isp which is about 92 to 94% of the
theoretical Isp calculated using "frozen at throat" assumptions.
These engines are all gas generator cycle. One reference suggests that for
LOX/kerosene engines similar to those described here, approximately 2% of total
propellant used is burned in the turbopump gas generator, and generates little
thrust. Pressure fed kerosene fueled engines or those with staged combustion
cycles would then be expected to yield approximately 2% higher Isp than
otherwise equivalent gas generator engines because of the lack of this
parasitic loss.
The J2
and SSME burn hydrogen and oxygen, and are optimized for vacuum operation
(although the SSME also operates in the overexpanded condition at takeoff). The
J2 engine is a gas generator engine, but no information is available on the
fraction of propellant used by the gas generator. In spite of using some
propellants in the gas generator, it yields 98% of the theoretical Isp. The SSME engine has an extremely effective
staged combustion cycle - the actual Isp is within a fraction of a percent of
the results of a "frozen at throat" Isp calculation.
Calculation
of Isp for under or over expanded engine.
Principle: For a given nozzle, the program calculates
both Isp (optimum), and Isp (vacuum).
The extra Isp in a vacuum comes from the additional thrust generated by
the difference between the exhaust pressure and ambient pressure (in this case
zero), times the area of the exit plane of the nozzle. For a given engine (when the area of the
exit plane is a constant), variations from Isp (optimum) are proportional to
the difference between the nozzle exit pressure and the ambient pressure. If for example a nozzle is calculated to
have an exit pressure of 10 psi, Isp (vacuum) minus Isp (optimum) for the
engine is proportional to 10-0=10. If
this same engine were operated in flight at an ambient pressure of 5 psi, then
the gain in Isp over Isp (optimum) would be half the gain realized in operating
in a vacuum. If however the engine were
operated at sea level (14.7 psi) then there would be a reduction in thrust due
to the difference in atmospheric pressure (the exit pressure is less than the
ambient pressure). The difference
between the calculated Isp (optimum) and the new effective Isp would be
proportional again to the pressure differential (14.7-10=4.7 psi), but in the
negative direction.
Let:
Pa =
ambient atmospheric pressure [specified by the investigator]
Pe =
exhaust pressure at the exit plane [listed as "pressure" in the
output tables]
Io =
Isp (optimum) [listed as
"Isp" in output tables]
Iv =
Isp (vacuum) [listed as "Isp (vacuum)" in output tables]
In =
Isp (non-optimum) [the Isp for under or overexpanded engines,
which is to be calculated]
then:
In =
[Io] +
[(Iv - Io) x (Pe - Pa)/(Pe - 0)]
in
words: the effective Isp for an under
or over expanded engine [In] equals the Isp for optimal expansion [Io], plus
how much Isp for that engine increases in a vacuum [Iv-Io] times the actual
pressure differential in question [Pe-Pa] divided by the pressure differential
associated with vacuum operation [Pe-0].
dropping
un-necessary brackets and the un-needed zero, which was inserted to make the
derivation of the equation clear, we get:
In =
Io +
(Iv - Io) x (Pe - Pa)/Pe
This equation
can be used to estimate the Isp of an engine which is not optimally
expanded. Note that when the engine is
under expanded, Pe is greater than Pa, and there is a gain in Isp. When Pe is less than Pa, there is a loss in
Isp.
****************************************************************************************
Propellants
in the library allprop.dat are as follows:
propellant
number /enthalpy of formation / density / chemical formula / names
1
-72.580 2.803 BRF3; BROMINE
TRIFLUORIDE
2 -109.590
2.460 BRF5 L; BROMINE PENTAFLUORIDE LIQUID
3
-37.300 1.587 CFN3O6; MFTNMF;
MONOFLUOROTRINITROMETHIDE
4 -139.100
1.200 CF4O2 L; BIS(FLUOROXY)DIFLUOROMETHANE
5
18.900 .000 CF5N3 L; PFG;
PERFLUOROGUANIDINE
6
-52.500 1.560 CF7N3; COMPOUND R;
TRIS(DIFLUOROAMINO)FLUOROMETHANE
7
-4.000 1.748 CF8N4; DELTA;
TETRAKIS(DIFLUOROAMINO)METHANE
8
-9.210 1.597 CHN3O6 L; TNM;
TRINITROMETHANE; NITROFORM
9
-27.030 .000 CH3NO2;
NITROMETHANE
10
8.800 1.640 CN4O8; TNM;
TETRANITROMETHANE
11
-31.190 1.650 C2H2N4O9;
TRINITROETHYL NITRATE
12
-67.340 .000 C2H3FN2O4;
1,1-DINITRO-1-FLUOROETHANE
13 -114.200
.000 C2H3FN2O5; 2-FLUORO-2,2-DINITROETHANOL
14
-47.000 .000 C2H4F4N2;
1,2-BIS(DIFLUOROAMINO)ETHANE
15
-34.670 .000 C2H4N2O4;
1,1-DINITROETHANE
16
-33.200 1.041 C2H5NO2;
NITROETHANE
17
-45.510 1.100 C2H5NO3; ETHYL
NITRATE
18
-80.530 .000 C3H5FN2O4;
1,1-BIS(DINITRO)-1-FLUOROPROPANE
19
-28.060 .000 C3H5N3O6;
1,1,1-TRINITROPROPANE
20
-35.800 1.800 NH4 N3O4; ADN;
AMMONIUM DINITRAMIDE; NH4 N(NO2)2; by SRI,1991, mp 95C, stable
21
-90.750 1.600 C3H5N3O9; NG;
NITROGLYCERINE; GLYCEROL TRINITRATE; O2NO-CH-[OCH2(NO2)]2
22
-51.000 .000 C3H6F4N2;
1,2-BIS(DIFLUOROAMINO)PROPANE
23
-39.900 1.261 C3H6N2O4;
1,1-DINITROPROPANE
24
-53.520 1.354 C3H6N2O4;
1,3-DINITROPROPANE
25
-44.450 1.807 CLF3; CTF;
CHLORINE TRIFLUORIDE
26
-39.600 1.852 CLF3O; FLOROX;
OXYCHLORINE TRIFLUORIDE
27
-60.500 1.779 CLF5; COMPOUND A;
CHLORINE PENTAFLUORIDE
28
-11.100 .000 HCLO4; PERCHLORIC
ACID
29
-5.391 1.560 CL2; CHLORINE
30
55.000 .000 CL2O7; CHLORINE
HEPTOXIDE
31
-3.098 1.505 F2; FLUORINE LIQUID
AT NBP
32
1.860 1.521 OF2; OXYGEN
DIFLUORIDE LIQUID AT NBP
33
-35.900 1.531 NF3; NITROGEN
TRIFLUORIDE LIQUID AT NBP
34
-41.460 1.503 HNO3; NITRIC ACID
35
-44.880 1.442 ;
HTP;PEROXIDE;HYDROGEN PEROXIDE
36
-4.680 1.431 N2O4; NTO; NITROGEN
TETROXIDE; DINITROGEN TETROXIDE
37
-3.102 1.149 O2; LOX; LO2;
LIQUID OXYGEN AT NBP
38
30.310 1.449 O3; OZONE LIQUID AT
NBP
39
-21.500 .550 ALB3H12; ABH;
ALUMINUM BOROHYDRIDE
40
4.970 .437 B2H6; DB; DIBORANE
LIQUID AT 180.59K (NBP)
41
7.740 .640 B5H9; PB;
PENTABORANE
42
-21.390 .424 CH4; METHANE
LIQUID AT NBP
43
-13.000 .000 CH5NO; METHOXYAMINE
44
12.950 .874 CH3N2H3; MMH;
MONOMETHYL HYDRAZINE; METHYL HYDRAZINE
45
49.270 .610 C2H2; ACETYLENE;
ETHYNE LIQUID
46
8.100 .569 C2H4; ETHYLENE
LIQUID AT NBP
47
10.180 .000 C2H4N4; AMMONIUM
DICYANAMIDE
48
22.470 1.149 C2H5N3O; 2-TRIAZOETHANOL
49
1.150 1.005 C2H6N2O;
N,N-DIMETHYL NITROSOAMINE
50
11.900 .786 C2H8N2; UDMH;
UNSYM-DIMETHYLHYDRAZINE
51
-54.600 .734 ALB3H19C2N;
HYBALINE A-4; ALUMINUM BOROHYDRIDE DIMETHYLAMINATE
52
36.190 .000 C3H3N; ACRYLIC
NITRILE; ACRYLONITRILE
53
63.100 1.091 HN3; HYDROGEN
AZIDE; HYDRAZOIC ACID
54
-2.154 .071 H2; LH2; HYDROGEN;
HYDROGEN LIQUID AT NBP
55
-17.090 .676 NH3; NH3 L;
AMMONIA L
56
12.050 1.004 N2H4; HYDRAZINE
57 -173.300
.804 C10H20; DECH; DIETHYLCYCLOHEXANE
58
-5.670 .830 ; JP-5
59
6.400 .680 SIH4; SILANE;
SILICON TETRAHYDRIDE AT NBP
60
-29.600 .585 C3H8; PROPANE;
LIQUID PROPANE
61
-23.750 .570 C2H6; ETHANE L
62
38.800 .700 C3H4;
METHYLACETYLENE LIQ
63
-5.760 .800 CH1.9532; RP-1;
KEROSENE; ROCKET PROPELLANT 1
64
-55.000 .736 ALB3H17CN;
HYBALINE A5; A5; ALUMINUM BOROHYDRIDE METHYLAMINATE; AL(BH4)3:CH3NH2
65
-60.000 .000 BEBH13CN; BEBHMA;
BERYLLIUM BOROHYDRIDE METHYLAMINATE; BE(BH4)2:CH3NH2
66
-2.939 .808 N2; NITROGEN LIQUID
AT NBP
67
-14.900 .000 ALB3H12; ABH;
ALUMINUM BOROHYDRIDE GAS
68
9.800 .000 B2H6; DB; DIBORANE
GAS
69
15.020 .000 B5H9 G; PB G;
PENTABORANE GAS
70
-13.970 .000 BRF; BROMINE
MONOFLUORIDE
71
-61.090 .000 BRF3 G; BROMINE
TRIFLUORIDE GAS
72 -102.470
.000 BRF5 G; BROMINE PENTAFLUORIDE GAS
73
-33.700 .000 CF4N2 G; PFF;
PERFLUOROFORMAMIDINE
74 -184.000
.000 CF4O G; FLUOROXYTRIFLUOROMETHANE
75 -134.600
.000 CF4O2; BIS(FLUOROXY)DIFOUOROMETHANE
76
24.200 .000 CF5N3 G; PFG;
PERFLUOROGUANIDINE
77 -107.500
.000 CF6N2; COMPOUND H; BIS(DIFLUOROAMINO)DIFLUOROMETHANE
78
-46.500 .000 CF7N3 G; COMPOUND
R GAS; TRIS(DIFLUOROAMINO)FLUOROMETHANE
79
2.600 .000 CF8N4 G; DELTA;
TETRAKIS(DIFLUOROAMINO)METHANE
80
80.100 .000 CH2N4 G; TETRAZOLE
GAS
81
-90.500 1.696 CF2N4O8;
1,1,2,2-TETRANITRO-1,2-DIFLUORIDE
82
-41.000 1.696 C2H4F4N2;
1,2-BIS(DIFLUOROAMINO)ETHANE
83
.000 .000 E; ELECTRON
84
-43.000 .000 C3H6F4N2;
1,2-BIS(DIFLUOROAMINO)PROPANE
85
-24.970 .000 C3H6N2O4;
1,1-DINITROPROPANE
86
-12.100 .000 CLF; CHLORINE
MONOFLUORIDE
87
-5.120 .000 FCLO3; PERCHLORYL
FLUORIDE
88
-37.970 .000 CLF3; CTF;
CHLORINE TRIFLUORIDE
89
-32.600 .000 CLF3O; FLUOROX;
OXYCHLORINE TRIFLUORIDE
90
-55.700 .000 CLF5; COMPOUND A;
CHLORINE PENTAFLUORIDE
91
-15.700 .000 NOF; NITROSYL
FLUORIDE
92
-19.000 .000 NO2F; NITRYL
FLUORIDE
93
2.500 .000 FNO3; FLUORINE
NITRATE
94
.000 .000 F2; FLUORINE
95
-32.000 .000 F2NH; DIFLUOROAMINE
96
5.860 .000 OF2; OXYGEN
DIFLUORIDE
97
-31.430 .000 NF3; NITROGEN
DIFLUORIDE
98
-35.900 .000 NF3O;
TRIFLUOROAMINE OXIDE
99
-5.000 1.660 N2F4; N2F4 L;
TETRAFLUOROHYDRAZINE LIQUID
100 -32.100
.000 HNO3; NITRIC ACID
101 70.260
.000 HN3; HYDROGEN AZIDE; HYDRAZOIC ACID
102 2.170
.000 N2O4; NITROGEN TETROXIDE
103 -70.690
1.950 NH4CLO4; AP; AMMONIUM PERCHLORATE
104 -87.270
1.725 NH4NO3; AN; AMMONIUM NITRATE
105
-120.000 .000 ALCL6N3O30; NAHP; NITRONIUM
ALUMINUM HEXAPERCHLORATE
106 -67.700
.000 CH2F2N2O; UDFU; UNSYM-DIFLUOROUREA
107 60.200
.000 CH2N6O2; 5-NITRAMINOTETRAZOLE
108 71.320
.000 CH2N6O2; NITROGUANYL AZIDE
109 -64.230
.000 CH3N3O3; NITROUREA
110 -21.760
1.775 CH4N4O2; NQ; NGu; NGU; NITROGUANIDINE; PICRITE
111 -6.590
.000 CH4N6O3; 5-AMINOTETRAZOLE NITRATE
112 3.790
.000 CH4N6O3; GUANYLAZIDE NITRATE
113 5.300
.000 CH5N5O2; NITROAMINOGUANIDINE
114 -17.200
1.850 CH5N5O6; HNF; HYDRAZINIUM NITROFORMATE
115 -36.460
.000 CH8N6O3; DIAMINOGUANIDINE NITRATE
116 -11.500
1.538 CH9N7O3; TAGN; TRIAMINOGUANIDINIUM NITRATE
117 -27.400
1.530 C2H3N3O6; 1,1,1-TRINITROETHANE
118 26.870
.000 C2H3N5O2; 3-NITRAMINO-1,2,4-TRIAZOLE
119 47.590
1.750 C2H4N6O8; TNEDA; N,N,N',N'-TETRANITROETHYLENEDIAMINE
120 -40.890
.000 C2H5N5O3; 3-AMINO-1,2,4-TRIAZOLE NITRATE
121 -35.100
.000 C2H5N5O3; 1-FORMAMIDO-2-NITROGUANIDINE
122 -23.650
1.750 C2H6N4O4; EDNA; ETHYLENE DINITRAMINE
123 26.590
.000 C2H7N9O2; GUANIDINONIUM-5-NITROAMINOTETRAZOLATE
124 28.600
2.250 C2N6O12; HNE; HEXANITROETHANE
125 -80.000
1.880 C3H2F12N8O; BTU; N,N'-DI(TRIS(DIFLUOROAMINO)METHYL)UREA
126 -38.600
.000 C3H4N4O8; 1,1,1,3-TETRANITROPROPANE
127 -45.300
1.300 C3H6N2O4; 2,2-DINITROPROPANE
128 14.690
1.816 C3H6N6O6; RDX; HEXAHYDRO-1,3,5-TRINITRO-S-TRIAZINE
129 -69.200
2.850 NOCLF4; NITROSYL TETRAFLUOROCHLORATE
130 -48.000
.000 NO2CLF4; NITRYL TETRAFLUOROCHLORATE
131 -66.340
2.126 NH4OCLO4; NH3OHCLO4; HAP; HYDROXYLAMMONIUM PERCHLORATE
132 -42.000
1.940 N2H5CLO4; HP; HYDRAZINIUM PERCHLORATE
133
-102.800 2.520 KCLO4; POTASSIUM
PERCHLORATE
134 -90.880
2.430 LICLO4; LITHIUM PERCHLORATE
135 -36.850
2.169 NOCLO4; NITROSYL PERCHLORATE
136 8.880
2.200 NO2CLO4; NP; NITRONIUM PERCHLORATE
137 -68.900
2.210 N2H6CL2O8; HDP; HYDRAZINIUM DIPERCHLORATE
138 -26.200
.000 NH2OH; HYDROXYLAMINE
139
-115.000 2.380 LINO3; LITHIUM NITRATE
140 .000
2.700 AL; ALUMINUM
141 -2.770
1.430 ALH3; ALUMINUM HYDRIDE
142 -26.200
.917 LIALH4; LAH; LITHIUM ALUMINUM HYDRIDE
143
-173.000 .000 ALH8N4NA; NAALAM; SODIUM
ALUMINUM AMIDE
144 -31.500
1.046 AL2H8MG; MAH; MAGNESIUM ALUMINUM HYDRIDE
145 -46.440
.681 LIBH4; LBH; LITHIUM BOROHYDRIDE
146 -45.650
1.080 NABH4; NABH; SODIUM BOROHYDRIDE
147 -41.630
.730 NH3BH3; AMMONIA BORANE; BORINE AMMONIATE
148 -25.800
.604 BEB2H8; BERYLLIUM BOROHYDRIDE
149 -30.000
.940 B2H10N2; B2H6.N2H4; HYDRAZINE DIBORANE
150 -46.000
1.000 B2H12N2; DIAMMINO DIBORANE
151 -49.000
.000 B3H10N; ATB; AMMONIA TRIBORANE
152 -10.000
.000 B8H28N4; DIHYDRAZINEBIS(DIHYDRIDOBORON)DI(TRIBOROHYDRIDE-8)
153 -15.800
.000 B10H14; DECABORANE
154 -87.130
1.000 B10H18N2; DEKAZENE; DODECAHYDRODECABORATE DIAMMINE
155 -71.000
.000 B10H22N4; DIDEKAZENE
156 -92.000
.000 B10H23N3; TRIS(AMMONIA)DECABORANE(14)
157 -23.300
.000 B10H24N6; H3D; DIHYDRAZINIUM PERHYDRODECABORATE HYDRAZINATE
158 -22.800
.000 B10H28N8; H4D; DIHYDRAZINIUM PERHYDRODECABORATE DIHYDRAZINATE
159 -2.000
.000 B10H30N8; TETRAKIS(HYDRAZINE)DECABORANE
160 10.000
.000 B10H34N10; PHDB; PENTAKIS(HYDRAZINE)DECABORANE
161 -4.400
.000 BEH2; BERYLLIUM HYDRIDE
162 -79.900
.000 LI2BEH4; DILITHIUM BERYLLIUM HYDRIDE
163 56.660
.000 CH2N4; TETRAZOLE
164 1.510 1.760 CH2N4O;
5-HYDROXYTETRAZOLE
165 49.670
1.650 CH3N5; 5-AMINOTETRAZOLE
166 57.600
1.560 CH8N6; TAG; TRIAMINOGUANIDINE
167 105.650
1.440 CH9N9; TAZ; TRIAMINOGUANIDINIUM AZIDE
168 47.900
.000 CH17B3N6; TRIAMINOGUANIDINIUM TRIBOROHYDRIDE-8
169 28.300
.000 CH23B9N6; TRIAMINOGUANIDINIUM NONABOROHYDRIDE-14
170 30.900
.000 CH26B10N8; TRIAMINOGUANIDINIUM DECABOROHYDRIDE-13-HYDRAZINATE
171 96.090
.000 C2HN5; 5-CYANOTETRAZOLE
172 48.070
.729 C2H2; ACETYLENE; ETHYNE SOLID
173 96.980
.000 C2H2N6; CYANOGUANYL AZIDE
174 18.360
.000 C2H4N4; 3-AMINO-1,2,4-TRIAZOLE
175 7.140
1.400 C2H4N4; DICYANDIAMIDE
176 16.510
.000 C2H4N4O; 5-METHOXYLTETRAZOLE
177 -69.910
.000 C2H4N4O2; AZODICARBAMIDE
178 135.140
.000 C2H4N10; 5,5'-HYDRAZOTETRAZOLE
179 46.260
.000 C2H5N5; 1-METHYL-5-AMINOTETRAZOLE
180 50.400
.000 C2H5N5; 2-METHYL-5-AMINOTETRAZOLE
181 48.410
.000 C2H5N5; 5-METHYLAMINOTETRAZOLE
182 40.560
.000 C2H5N7; 5-GUANYLAMINOTETRAZOLE
183
-119.190 .000 C2H6N4O2;
HYDRAZODICARBAMIDE
184 106.800
1.420 C2H8N8; DIAMINOGUANIDINIUM AZIDE-FORMALDEHYDE POLYMER; DAZAL
185 45.210
.000 C2H8N10O; 1-(5-TETRAZOLYL)-4-GUANYLTETRAZENE HYDRATE
186 -30.400
.000 C2H10BN; DIMETHYLAMINE-BORANE ADDUCT
187
-100.000 .000 C2H24B10N4;
BIS-(METHYLHYDRAZINO)DECABORANE
188 60.000
.000 C2H28B10N12; BIS-(TRIAMINOGUANIDINIUM)PERHYDRODECABORATE
189 -9.000
.000 LIC2N3; LITHIUM DICYANAMIDE
190 -1.210
.000 C3H5N5O; 5-ACETAMIDOTETRAZOLE
191 12.720
.000 C3H5N5O2; 3-NITRAMINO-5-METHYL-1,2,4-TRIAZOLE
192 45.080
.000 C3H6N4; 1,5-DIMETHYLTETRAZOLE
193 -6.690
.000 C3H6N4O; 1,4-DIMETHYL-5-TETRAZOLONE
194 -2.160
.000 CSN3; CESIUM AZIDE
195 -21.670
.820 LIH; LITHIUM HYDRIDE
196 27.140
1.346 NH3N3; AMMONIUM AZIDE
197 142.100
.000 HG2N6; MERCUROUS AZIDE
198 -.400
2.040 KN3; POTASSIUM AZIDE
199 2.790
.000 LIN3; LITHIUM AZIDE
200 5.180
1.850 NAN3; SODIUM AZIDE
201 115.900
.000 PBN6; LEAD AZIDE
202 .000
1.850 BE; BERYLLIUM
203 -5.576
.000 BEH2.0356O.008C.0228; BERYLLIUM HYDRIDE 96%
204
-104.000 .660 BE26H59C4; BERYLLIUM
HYDRIDE 83%
205 -50.800
.000 BE8.6542H17.6277C.3522; BERYLLIUM HYDRIDE 93%
206 -40.100
.650 BE8.7182H17.8334C.2601O.0202; BERYLLIUM HYDRIDE 95%
207 .000
2.320 B; BORON
208 .000
.534 LI; LITHIUM
209 .000
1.740 MG; MAGNESIUM
210 -17.000
1.450 MGH2; MAGNESIUM HYDRIDE
211 .000
.970 NA; SODIUM
212 -13.700
.000 NAH; SODIUM HYDRIDE
213 .000 11.337 PB; LEAD
214 .000
2.046 S; SULFUR
215 .000
2.400 SI; SILICON
216 .000
4.500 TI; TITANIUM
217 .000
6.400 ZR; ZIRCONIUM
218 -27.600
.000 B10H10C2H2; CARBORANE
219 -22.000
.000 C4H12NB3H8; TETRAMETHYLAMMONIUM TRIBOROHYDRIDE
220 -44.000
.000 LIAL6H19; LITHIUM ALUMINUM HYDRIDE-ALUMINUM HYDRIDE ADDUCT
221 -64.000
.000 LIAL11H34; LITHIUM ALUMINUM HYDRIDE.10ALUMINUM HYDRIDE ADDUCT
222 -18.000
.000 ZRSI; ZIRCONIUM SILICIDE
223 -12.000
.000 ZRSI2; ZIRCONIUM DISILICIDE
224 -25.000
1.140 C17H20N2O; EC; ETHYL CENTRALITE
225 26.300
.000 C6H8N2; ADIPONITRILE
226 -75.000
.500 ALB9H24; ALUMINUM TRIBOROHYDRIDE
227
-132.000 1.800 ALB3H14C1O; ABHPMO;
ALUMINUM BOROHYDRIDE POLYMETHYLENE OXIDE; AL(BH4)3:CH2O
228
-177.400 .710 ALB3H20C4O2; ABHBPMO;
ALUMINUM BOROHYDRIDE BISPOLYETHYLENEOXIDE; AL(BH4)3:2C2H4O
229 -15.000
.000 LIAL; LITHIUM ALUMINUM
230 -48.000
.000 CH2O; WOOD
231 -42.000
.000 LIBEH3; LITHIUM BERYLLIUM HYDRIDE
232
-138.800 .000 C3H4O3; ETHYLENE
CARBONATE
233
-109.770 .000 C3H5NO4;
METHYLNITROACETATE
234
-197.300 5.120 FE2O3; FERRIC OXIDE;
HEMATITE
235
-195.200 2.310 C2F4; TEFLON;
POLYTETRAFLUOROETHYLENE
236 -12.700
.900 C2H4; PE; POLYETHYLENE
237 -6.350
.900 CH2; PE; POLYETHYLENE
238 .250
.000 C2H6N2; PEH; POLYETHYLENEHYDRAZINE
239 -47.800
1.610 C2.238H3.24F2.114N1.094; PBEP; POLY
(1.2-BIS(DIFOUOROAMINO)-2,3-EPOXYPROPANE)
240
-113.000 .000 C3H5NO; POLYACRYLAMIDE
241 -30.750
.000 C3H5NO2; 2-NITROPROPENE POLYMER
242 63.100
.000 HN3; HN3 GAS; HYDROGEN AZIDE; HYDRAZOIC ACID
243 70.260
.000 HN3; GAS
244 129.500
1.180 C8H8; CUBANE
245 139.500
1.180 C8H8; CUBANE; CUBANE WITH HT OF FORM BIASED TOWARD ARIES CLAIM
246 149.500
1.180 C8H8; CUBANE; CUBANE WITH ARIES HT OF FORMATION
247 44.310
.000 C3H4; METHYLACETYLENE GAS
248
-118.100 3.685 CSNO3; CESIUM NITRATE
249 -2.000
.000 N2F4; N2F4 G; TETRAFLUOROHYDRASZINE GAS
250 1.300
.000 PH3; PH3 G; PHOSPHINE GAS
251 -1.200
.000 P2H4; P2H4 L; DIPHOSPHOROUS TETRAHYDRIDE LIQ
252 5.000
.000 P2H4; P2H4 G
253 34.000
1.300 C3H5N3O; GAP; GLYCIDYLAZIDE POLYMER; -OCH2CH(CH2N3)-
254
-145.400 1.329 C6H12N2O8; TEGDN;
TRIETHYLENEGLYCOL DINITRATE
255 -7.400
1.210 C7H8N2O2; MNA; N-METHYL-P-NITROANILINE; CH3NH-Ph-NO2
256 .000
1.800 C; GRAPHITE
257
-123.000 1.667 C2H4N2O2; OXAMIDE;
OXAMIDE S; OXALAMIDE; ETHANEDIAMIDE; OXALIC ACID DIAMIDE
258
-257.500 1.132 23H38N6O5; N-100
259 -75.270
1.040 C8H12N2O2; HDI; HMDI; HEXAMETHYLENE DIISOCYANATE; OCN-(CH2)6-NCO
260
-313.200 1.330 C15H21FEO6; FE(AA);
FE(AA)3; FERRIC ACETYLACETONATE; ((CH3CO)2CH)3FE
261 18.000
1.930 C4H8N8O8; HMX; CYCLOTETRAMETHYLENETETRANITRAMINE; "HER
MAJESTY'S EXPLOSIVE"
262
-100.000 1.488 C5H9N3O9; TMETN; METN;
METRIOL TRINITRATE; 1,1,1-TRIMETHYLOLETHANE TRINITRATE
263 -89.500
1.520 C4H7N3O9; BTTN; 1,2,4-BUTANETRIOL TRINITRATE
264
-118.700 1.800 C3H7CLF6N4O; INFO 631C;
2-TRIS(DIFLUORAMINO)METHOXY)ETHYLAMINE HYDROCHLORIDE
265
-113.600 1.800 C3H7CLF6N4O5; INFO 635P;
2-TRIS(DIFLUORAMINO)METHOXY)ETHYLAMINE PERCHLORATE
266 .000
.000 CH.681O.069N.011S.003SI.009; COAL
267
-178.000 1.600 C5H6F2N4O10; FEFO;
[F(NO2)2CCH2O]2CH2
268
-230.000 1.650 C7F6H8N6O10; SYEP;
[FC(NO2)2CH2OCH2]2-C(NF2)2
269
-268.300 1.640 C11H14F10N8O10; SYFO;
[FC(NO2)2CH2CH2C(NF2)2CH2O]2-CH2
270 -2.970
.900 C7.337H10.982O.058; R-45M; HTPB; HYDROXY TERMINATED POLYBUTADIENE
271
-249.000 3.520 FEF3; FERRIC FLUORIDE S
272 -52.510
9.530 PBO; LEAD MONOXIDE; LITHARGE; RED PBO
273 -52.120
8.000 PBO; LEAD MONOXIDE; MASSICOT; YELLOW PBO
274 -65.600
9.375 PBO2; LEAD DIOXIDE; PLATTNERITE
275
-171.770 9.100 PB3O4; LEAD
ORTHOPLUMBATE; TRILEAD TETRAOXIDE; RED LEAD OXIDE
276
-102.000 1.377 C4H8N2O7; DEGDN;
DIETHYLENE GLYCOL DINITRATE; O2NOCH2CH2OCH2CH2ONO2
277 -58.300
1.480 C2H4N2O6; EGDN; ETHYLENE GLYCOL DINITRATE; O2NOCH2CH2ONO2
278 -83.100
1.376 C3H6N2O6; PGDN; PROPYLENEGLYCOL DINITRATE; O2NOCH2CH(ONO2)CH3
279 -92.500
1.436 CH6N4O3; GN; GUANIDINE NITRATE
280
-172.200 1.653 C6H7.68N2.32O9.645; NC; NITROCELLULOSE;
12.2%N (NC); PYROXYLIN; CELLULOSE NITRAE
281
-164.800 1.650 CH7.365N2.64O10.29; NC;
NITROCELLULOSE; GRADE C NC; TYPE INC; 13.15%N (NC)
282 -18.200
1.220 C9H6N2O2; TDI; TOLUENE DIISOCYANATE
283
-207.190 1.540 C9H14F12N6O3; TVOPA;
[[CH2(NF2)CH(NF2)O]CH2]2-CH-[OCH(NF2)CH2(NF2)]
284 -88.800
1.060 C12H18N2O2; IPDI; ISOPHORONE DIISOCYANATE
285
-117.760 2.100 KNO3; KN; POTASSIUM
NITRATE; SALTPETER; NITER; NITRE; SALPRUNELLA
286
-184.000 1.120 C12H14O4; DEP; DIETHYL
PHTHALATE
287
-203.900 1.045 C16H22O4; DBP; DIBUTYL
PHTHALATE
288
-161.200 1.190 C10H10O4; DMP; DIMETHYL
PHTHALATE
289 -87.950
1.200 C6H6O2; RESORCINOL; RESORCIN; 1,3-BENZENEDIOLE
290 17.000
1.366 C12H10N2O2; 2-NDPA; 2-NITRODIPHENYLAMINE
291 34.350
1.600 C12H11N; DPA; DIPHENYLAMINE
292
-223.600 1.080 C9H18N3OP; MAPO;
TRISMETHYLAZIRIDINYLPHOSPHINEOXIDE; O=P[NCH2CHCH3]3
293
-316.100 1.160 C9H14O6; TA; TRIACETIN;
GLYCERINE TRIACETATE; [CH3COOCH2]2-CH-OCOCH3
294
-343.620 2.662 K2SO4; POTASSIUM SULFATE
295
-209.500 .870 C19H38O2; IDP; ISODECYL
PELARGONATE; CH3(CH2)7COO(CH2)7CH(CH3)2
296 9.990
1.270 C27H32FE2; CATOCENE; 2,2-BIS(ETHYLFERROCENYL)PROPANE;
[C2H5(C5H5)2FE]2-C(CH3)2
297
-424.000 1.400 C36H70O4PB; PBST; LEAD
STEARATE; [CH3(CH2)16COO]2=PB
298 -48.500
6.900 ZRC; ZIRCONIUM CARBIDE
299
-184.000 3.650 CUSO4; COPPER SULFATE;
CUPRIC SULFATE
300 -91.000
.900 C8H24B10; NHC; N-HEXYL CARBORANE; CHB10H10C(CH2)5CH3
301
-143.470 1.080 C23H32O2; AO 2246;
antioxicant 2246
302
-390.000 1.200 C15H22O8; CAB; CELLULOSE
ACETATE/BUTYRATE
303
-341.000 1.300 C12H16O8; CA; CELLULOSE
ACETATE
304 33.800
1.490 C10H10FE; FERROCENE; [C5H5]2=FE
305
-399.000 3.970 AL2O3; ALUMINUM OXIDE;
ALUMINA; CORUNDUM
306 304.000
1.240 C14H24N18O4; GAP-A; GLYCIDYL AZIDE-A POLYMER
307 -8.260
.900 C7.1158H11.003N.1291O.0989S.0015; HT BIND
308 -82.800
1.010 C5.117 H9.586 O1.684 N.138; POLYU; POLYURETHANE
309
-726.700 1.850 C11F14H8; VITON
310 -16.700
1.500 C2.53 H4.1 N1.64 O2.66; NPU; NITROPOLYURETHANE
311
******** 1.500 C64H94N34O18F64; SBM;
[-CH(C2H3N2F4)CH2O-]15-CONHC2H2N2F4NHCOO-
312 -43.675
1.610 C2.451 H3.276 O.879 N1.096 F1.992; PBEP XL; CROSSLINKED PBEP
313 -51.400
.000 C2F3CL; KELF; KELF POLYMER
314 62.000
1.868 C6 H4 N6 O12; HNH; HEXANITROHEXYNE; [CCH2C(NO2)3]2; mp 130, stable
(Thiokol)
315 -68.100
.967 C4.167 H11.745 O.636 B6.745; 43 B; 43% BORON BINDER; 1 C10H22O4B10+
1 C5H16B10
316 -44.200
1.027 C2.618 H8.774 O.348 B5.004; 55 B; 55% BORON BINDER; see 43B
317 -39.700
1.000 C2.15 H9.106 B6.007; 65 B; 65% BORON BINDER; see 43 B
318
-311.630 .927 C22 H42 O4; DOA; DIOCTYL
ADIPATE PLASTICIZER
319
-344.210 .910 C26 H50 O4; DOS; DIOCTYL
SEBACATE PLASTICIZER
320 -41.500
2.000 NH3OHCN3O6; HANF; HYDROXYLAMMONIUM NITROFORM; hypothetical
material
321 -2.650
2.187 AL1.854MG2.056; AL/MG; 50/50 AL/MG ALLOY
322 -.270
2.400 MGAL2; MAGNESIUM/ALUMINUM ALLOY; (density is estimated)
325 -68.300
1.000 H2O;
*****************************************************
HELP
SCREENS
A
variety of help screens are available for the input program. They are contained in the file hlp.doc,
which is read by the program inp.exe when it is executed, and which are
displayed when help is asked for while running inp.exe. Below are the help screens, extracted from
the file hlp.doc, and rearranged for easier viewing.
This
marks the end of material written by Dr. Bruce Dunn
******************************************************
INPUT
UTILITY FOR SPECIFIC IMPULSE CODE
by Curtis Selph
This program
helps the user generate an input run file for the Air Force
Chemical
Equilibrium Specific Impulse (Isp) Code.
When you have finished, you
must
exit this utility and invoke Isp. It
will query you for the name of the
run
file created here.
A second
use of this program is to enable editing of the Master Propellant
Data
Library. The two functions are
distinct. Changes to the Master Library
cannot
be made while in the run file preparation mode; and a run file
cannot
be prepared while in the Master Library edit mode. However, you may
search
the Master Library while creating a run file, and transfer propellant
data
into the run library.
This
utility is still a "work in progress". No warranties are expressed or
implied. There is no manual on its operation. The user is assumed to be
curious
enough to read the screen, and bold enough to press the keys. It is
unlikely
that anything bad will happen that is beyond the remedy of a soft
re-boot. Harsh criticism is in bad taste, but gentle
inquiry or warm praise
may be
directed to the author, last known phone number: (805) 275-5320
UNDERSTANDING
THE OPTIMIZER:
The
optimizer is a feature of the Isp program that steps the propellant
proportions
through specified ranges in a systematic way, and watches the
behavior
of some specified optimization parameter, usually Isp. The course of
the
stepping process is influenced by the optimization parameter, so as to
determine
directions to the peak and to shut off the stepping when a peak has
been
found. The output of the process is a
series of Isp calculations
containing
a highest value that must be found by inspection. The inspection
is
greatly facilitated by calling for a summary output tabulation, described
in the
input/output options available from the main menu. Since a
multidimensional
optimization can generate a lot of output from a disarmingly
compact
input, it may also be useful to suppress the normal output and rely on
just
the summary. Unless otherwise
specified, the optimization parameter is
the
"optimum back pressure Isp" for the last calculated exit station.
SOME
NOMENCLATURE TO BE USED IN THIS DISCUSSION:
An
INGREDIENT is defined by a single entry in the propellant run library. It
is a
fuel, an oxidizer, binder, or additive.
A
MIXTURE is the full collection of INGREDIENTS that are injected together
into a
chamber, or that are mixed to form a solid propellant.
PROPORTIONS
are relative amounts of the ingredients that make up a mixture.
EXAMPLE:
the
"MIXTURE" 2 OXYGENS + 1
HYDROGEN
is composed of the
"INGREDIENTS" OXYGEN
AND HYDROGEN
with
"PROPORTIONS" 2 AND
1
The PROPORTIONS
may be taken as masses or moles (or even as volumes if
accurate
ingredient densities have been input). It is your choice, and you
will be
queried for your intent.
Unlike
tabular input, optimizer input does not specify PROPORTIONS directly.
Rather
the input consists of a series of RELATIONSHIPS--exactly one for each
ingredient
in the mixture. Taken together these
relationships must be
sufficient
to define the PROPORTIONS of a MIXTURE.
The
scheme described below was conceived to provide generality in doing
multi-dimensional
optimizations of complex mixtures. The
examples include
simple
bipropellant optimizations to emphasize that the scheme reduces to a
simple
input when the problem itself is simple.
The
term COMPONENT has been selected to represent any useful subdivision of a
MIXTURE. The membership of a COMPONENT can be as
small as a single ingredient
or as
large as the complete mixture. It is
the inputters job to decide what
constitutes
a useful collection of COMPONENTS in the context of his desired
optimization. COMPONENTS go hand in hand with
RELATIONSHIPS. The most common
RELATIONSHIP
simply states the AMOUNT of a COMPONENT:
RELATIONSHIP COMPONENT
= AMOUNT
EXAMPLE 1 1 LH2 =
1.0
2 LO2 = 4.0
RELATIONSHIP COMPONENT
= AMOUNT
EXAMPLE 2 1
N2H4+UDMH = 1.0
2 N2H4 = 0.5
3 N2O4 = 2.0
EXAMPLE 3 1
AP+PE+AL = 100.0
2 PE = 15.0
3 AL = 20.0
Notice that
in the second example, N2H4 appears in the COMPONENT (N2H4+UDMH)
of the
first relationship, and also in the unit COMPONENT (N2H4) of the second
relationship. Expressed in this way, the N2H4 proportion
can be changed (more
about
this later), and the UDMH proportion will automatically change to keep
the
total fuel COMPONENT at 1.0. Similarly
in example 3, the proportion of AP
would
automatically change in response to any change in PE or AL so as to keep
the
total propellant equal to 100.0.
Examples 1 and 2 illustrate adherence to
liquid
propellant conventions that set the fuel content to 1.0 (O/F convention)
whereas
example 3 represents a typical solid propellant convention,in which
proportions
sum to 100.
Although
the program's querying process is automatic, you as analyst must
obviously
give some forethought as to how the problem is to be set up, and
what
normalizing conventions you will adhere to.
FIXED
VS OPTIMIZATION RELATIONSHIPS: Among
the first program queries is
whether
the RELATIONSHIP in question is FIXED, as in the above examples, or
whether
it will represent the INITIAL condition from which changes are to be
made as
part of an OPTIMIZATION. If the
relationship is an optimization, then
the
program will query you for three more parameters, which represent the
minimum
value of the AMOUNT you wish to be considered, its maximum value, and
the
step size for the changes.
Problems
may be one-dimensional optimizations:
RELATIONSHIP COMPONENT=
AMOUNT
1
N2H4 = 0.5
2 MMH = 0.5
INITIAL LOWER UPPER
STEP
AMOUNT LIMIT LIMIT
SIZE
3 N2O4 =
2.0 1.4 3.0
0.2
Or
multi-dimensional optimizations:
RELATIONSHIP COMPONENT
AMOUNT
1 N2H4+MMH = 1.0
INITIAL LOWER
UPPER STEP
AMOUNT LIMIT LIMIT
SIZE
2 N2H4 = 0.5 0.1 0.9 0.1
3 N2O4 = 2.0 1.4 3.0 0.2
In the
two-dimensional optimization above, the N2O4 relationship is listed
below
the N2H4 relationship, which causes it to vary most rapidly. That is,
it is a
subset of the optimization connected with N2H4, and would be
re-optimized
for each value of N2H4. The complete
optimization would be found
by
comparing the peaks in the optimization parameter (such as Isp), for each
of the
N2H4 amounts. Larger ingredient sets
with larger optimization
dimensions
are possible. These are accommodated in
the Isp program by
systematically
working upward in the list of relationships, satisfying all
subsidiary
optimizations as many times as neccessary.
At least one of the
relationships
must be fixed, and all fixed relationships are listed before
any optimization
relationships.
The
above discussion highlighted relationships based on "AMOUNT" of a
COMPONENT.
The second type of relationship tool is based upon the RATIO of two
COMPONENTS:
(N2O4) / (N2H4) = RATIO
Note
that this example is not a complete specification, since it contains one
relationship
and two ingredients. In most cases a
problem can be set up using
either
"AMOUNT" or "RATIO", with entirely equivalent results. "AMOUNT"
relationships
are simpler to input, because they contain only one COMPONENT;
and
they can be used for the majority of problems, including all bi-propellant
systems. AMOUNT and RATIO relationships may be used
together in an
optimization. Indeed all optimizations must have at least
one relationship
based
upon AMOUNT, in order to establish the normalizing convention. In
general,
the only time that a relationship based upon RATIO is needed is for
the
case in which a COMPONENT is put in a RATIO to another COMPONENT that is
itself
a variable:
1 (N2H4) = 1.0
2 (NO) / (N2O4 + NO) = .06, .02, .10,
.02
3 (N2O4 + NO) = 1.6, 1.0, 2.0,
.2
In this
optimization, the second relationship is chosen to be a RATIO
relationship,
because it is desired to hold the NO at a series of controlled
RATIO's
to a COMPONENT (N2O4+NO) that itself varies during the optimization.
The
specific effect desired cannot be simulated using only AMOUNT
relationships.
It may
be helpful to know how the Isp code uses your inputs. It will start
from
the initial AMOUNT (or RATIO) and systematically step through the
indicated
range, first downward. If downward
yields a lower Isp (or whatever
is
being optimized), it will reverse direction and step upward. It quits when
it
crosses a peak or bumps into a limit.
There is merit in guessing an
initial
AMOUNT or RATIO close to the peak.
It may
be noticed that the relationships discussed above are all linear
equations,
and that the coefficients are always unity.
The program also
offers
the opportunity to apply non-unity coefficients (called weighting
factors). This gives maximum generality for describing
a desired
optimization;
but it is unlikely that the general user will ever encounter a
problem
that requires or benefits from non-unity coefficients. Nevertheless,
he
should be aware of its existence, in case he or she can think of no other
way. In such an instance, the capability may be
accessed by answering "yes"
to the
query relating to "weighting factors".
SPECIAL FIGURES OF MERIT
Several
figures of merit (FOM) have been invented to combine the effects of
specific
impulse and propellant density into a single "measure of goodness".
All
have their limitations, usually attributable to omitted hardware and
mission
considerations. Three such FOM are
offered in the Isp program, which
cover a
range of applicability, rigor, and amount of hardware and/or mission
input
specification.
These
FOM are NOT a part of the standard output.
They can only be obtained
as
output by calling for them from the "CONDENSED SUMMARY OF OUTPUT"
under
"INPUT/OUTPUT
OPTIONS" menu item.
The
simplest SPECIAL FIGURE OF MERIT is the density-Isp (ISP*RHO), obtained
by
multiplying the specific impulse and the propellant bulk density together.
The
only necessary additional input is a specification of the Isp to be
used--not
its value, but its location in the standard output. Recall that
there
are two rows of Isp:
Isp at P(ambient) = P(exit)
Isp at P(ambient) = Vacuum
and an
entry for both under each exit station.
.
.
For
most applications, ISP*RHO overstates the importance of density. It is
most
applicable for non-accelerating cruise missions that are volume limited.
DELTA V
The
second SPECIAL FIGURE OF MERIT is the DELTA V, sometimes known as boost
velocity. It is obtained by solving the integrated
form of the momentum
equation
for mass ejection at constant ejection velocity:
DELTA V = Ve * Ln (Mi/Mf)
where
Mi is the vehicle initial velocity, Mf is its final velocity, Ln is the
natural
logarithm, and Ve is the exit velocity of the combustion gases. Ve is
equivalent
to the Isp times the gravitational constant, gc, 32.174 ft/sec in
engineering
units.
DELTA V
becomes related to propellant density by assuming that there is a fixed
hardware
mass for each unit of enclosed propellant volume. This ratio of mass
to
volume has units of density and may be taken as a hardware figure of merit.
If it
is assigned the same units as the propellant density, the DELTA V
equation
can be put in the form
DELTA V = Isp * gc * Ln (1 +
RHOP/RHOH)
where
RHOP is propellant density, and RHOH is "hardware density", as
explained
above.
DELTA V
requires the specification of the location of the Isp to be used and
the
value of the "hardware density".
The default value of RHOH is
.12
grams/cc. The value of RHOP is calculated
from the ingredient densities
and
their amounts in the propellant.
Note
that the first DELTA V expression (using Mi/Mf) is rigorous for a
drag-free,
gravity-free accelerating mission. In
its second form its accuracy
is
burdened by an additional assumption.
Not all the hardware encloses
propellant,
and so not all the hardware mass will scale with propellant volume,
as
assumed. A rough justification for this
frequently made assumption is that
other
mass terms will also scale with propellant volume, albeit for different
reasons,
and in more complex ways. The usual effect of the assumption is that
the
calculated DELTA V will overstate the importance of density.
One of
the drawbacks of the DELTA V figure of merit is that the hardware mass
includes
any payload carried, confounding the desire to define inputs that
depend
only upon the propulsion system. The
default input for RHOH, for
example,
is typical of a propulsion stage without a payload, and the derived
DELTA V
is thus for a payload-less rocket. This
drawback is overcome in the
next
figure of merit with only a relatively minor additional complication:
M(payload) /
M(booster)
Shortened
in the program to PAY/BSTR for output purposes. One use for this
parameter
would be to assume it as an input and use the it to refine the
calculation
of DELTA V. This seems more arbitrary
than turning the action
around,
and selecting a DELTA V characteristic of some mission of interest.
The
calculation of PAY/BSTR then follows from a re-formulation of the DELTA V
equation
PAY/BSTR = ( R/(F-1)
- 1 ) / (R-1)
where R = RHOP / RHOH
and F = exp ( (DELTA
V) / (ISP * gc) )
The parameter
PAY/BSTER is preferable to the previous two figures of merit,
but it
also suffers from the assumption that RHOH/RHOP is a constant. The
assumption
is probably least offensive for solid propelled rockets, in which
the
propellants are enclosed by a high pressure vessel (the combustion
chamber),
whose mass does scale with propellant volume and is large enough
to more
nearly dominate other terms. Also,
solid propellants do not vary
across
such large density ranges. There is
thus some hazard in using the
PAY/BSTR
parameter for comparing solid and liquid rockets, or liquid storable
rockets
with less dense liquid cryogenics. The
errors introduced again tend
to
overemphasize the importance of density.