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Apparent Flight Mach
4
3.5
3
2.5
2
1.5
1
0.5
MIPCC
off
MIPCC on
0
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5
Actual Flight Mach
Figure 13: Apparent Mach Number Experienced by Turbo Machinery as a Function of Actual Flight
Mach Number[6].
As these figures indicate the MIPCC system engages at Mach 0.9 and continues to
operate throughout the trajectory. At Mach 4 and 88,000 ft the engine performs as if it is
operating at an altitude of 24,000 ft and a Mach number of 1.6.
Unfortunately the MIPCC concept does have drawbacks. First the increased
weight of the oxygen and water carried increases the vehicle size. Also these propellants
have to be stored in separate tanks and therefore further increase the vehicle dry weight.
Also the Isp of the engines cannot be computed from a simple translation of the TBEAT
data. As the tanked water and oxidizer flow rate increases, the Isp of the engine must be
adjusted to account for the additional mass flow. This was accomplished by first
calculating the MIPCC propellant flow rate as a function of SLS fuel flow rate according
to Figure 14. This data was then curve fit so the MIPCC propellant flow rate could be
calculated at every Mach number and altitude. This curve fit was broken up into four
regions two for each type of tanked MIPCC propellant. In three of the four cases a linear
fit produced a good representation of the data, but for the initial water injection profile a
cubic polynomial was used to fit the data. These curve fits are also provided in Figure
16