# ENAE 483/788D

Principles of Space Systems Design

Fall, 2002

Question 7:

Assume that the two-stage Saturn V augmented with four Space
Shuttle Solid Rocket Boosters from Problem 5 could carry 200,000
kg to low Earth orbit. (I'm not saying that this is necessarily
the right answer to Problem 5, just that you should assume it
for this problem.) Your task is to design an upper stage for this
launch vehicle which will maximize the payload injected into a
Mars transfer orbit. The upper stage you are designing will use
LOX/LH_{2} propellants with an I_{sp} of 455 sec.
The payload of the augmented Saturn V will consist of the upper
stage and the Mars payload. Once in low Earth orbit, your upper
stage will have to provide a delta-V of 3.644 km/sec to inject
the Mars payload into the proper trans-Mars trajectory.

a) Assume the inert mass fraction for the upper stage is 0.08.
Calculate the stage inert mass and propellant mass, and the mass
of the Mars payload.

b) Using the mass estimating relations from Lecture 10, find
the following system masses:

- Oxidizer tank
- Oxidizer tank insulation
- Fuel tank
- Fuel tank insulation
- Forward fairing
- Intertank fairing
- Aft fairing
- Avionics
- Wiring
- Rocket engine(s)
- Thrust structure
- Gimbals

__Clearly__ list any and all design choices or assumptions
you make. Some details you will need for the design process:

- The second stage to which you attach has a diameter of 10
meters. The payload has a diameter of 7 meters. You do not have
to account for a payload fairing (the aerodynamic shell around
the payload is taken care of by the payload), but you do have
to have adapter sections so that the two ends of your stage are
the same diameter as the components they connect to.
- Assume an initial T/W ratio of 0.5. The expansion ratio is
50:1. The chamber pressure is 2500 psi.

c) Tabulate your results, and incorporate a 30% margin for
growth. Calculate the new payload mass, and calculate the actual
value of inert mass fraction this represents.

d) Sketch the internal layout of your stage.