Analysis: CM
y – int2 = 9386 – (– 30.75)(15) = 9386 + 461.25 = 9, 847.25
Spacecraft habitat weight depends on many
factors, such as the number of astronauts needed
or the duration of the mission. Some CM component
weights will vary depending on these factors (such as
Environmental Control and Life Support Systems), while
others will weigh the same no matter what (such as the
CM structure itself).
The Space Tug CM graphic shows that a crew of
Therefore, the two linear equations for the Boeing
Space Tug CM are:
the CM would have weighed 9,386 pounds, whereas
would have included the weight of the crew). These
numbers look suspiciously like points on a Cartesian
graph, which means that they may be linear equations.
variable. Therefore we get the points (3, 50) & (15, 2)
and (3, 9755) & (15, 9386). We can thus calculate the
slope and the y-intercepts of the two linear equations.
2 – 50
–48
Slope1 = ––––––– = –––– = –4
15 – 2
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Example
Suppose you want to take a crew of 10 astronauts
on a space mission to the Moon. What would be the
what is the weight of the CM?
Using the linear equations that we just derived, we
plug in Crew = 10 into the equations.
Mission Duration = – 4(10) + 62 = 22 Days
So for this particular design, a crew of ten would
have allowed the spacecraft to stay aloft for about
three weeks, and would have weighed under 10,000
pounds. Very nice!
Slope2 = 9386 – 9755 = –369 = – 30.75
–––––––––––––
–––––
15 – 3
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www.RocketSTEM .org
WeightCM = –0.75Crew + 9847.25
WeightCM = – 30.75(10) + 9847.25 = 9, 540 lbs
y–int1 = 2–(–4)(15) = 2 + 60 = 62
Diagram of the Boeing Space Tug Crew Module (CM).
Mission Duration = 4Crew + 62
Credit: Boeing
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