Spacecraft Design and
Sizing
Dr Andrew Ketsdever
MAE 5595
Lesson 14
Spacecraft Design and Sizing
Sizing Introduction
• Big Picture: The Mission
drives the Payload and the
Orbit, which drives the
Spacecraft Design
Spacecraft Design and Sizing
Overview of Spacecraft Design &
Sizing
Spacecraft Design and Sizing
Principal Requirements & Constraints for S/C
Design
Spacecraft Design and Sizing
Principal Requirements & Constraints for S/C
Design
Spacecraft Design and Sizing
Weight Budget
Spacecraft Design and Sizing
Spacecraft Configuration Drivers
Spacecraft Design and Sizing
• Can use
historical data for
next block of
same S/C, or to
generalize within
a mission type
Spacecraft Design and Sizing
Mass Distribution for Selected
Satellites
Spacecraft Design and Sizing
Spacecraft Design and Sizing
Mass Distribution for Selected
Satellites
Spacecraft Design and Sizing
Top-Down Sizing Example
• Given: navigation mission with mP/L = 50 kg
• Find: subsystem masses and mdry
%m P / L
mP / L

 0.2122
mdry
%m propulsion  0.0319

 %m ADACs  0.0561
 %mTT &C  0.0471
mbus 
 %m EPS  0.3206
 %mTCS  0.0986

 %mstructure  0.2345
Check : mbus  m P / L  mdry

mdry  235.6 kg
m propulsion  7.5 kg 
m ADACS  13.2 kg 
mTT &C  11.1 kg 
  185.7 kg
m EPS  75.5 kg 
mTCS  23.2 kg 

mstructure  55.2 kg 
Spacecraft Design and Sizing
Top-Down Sizing Example
• Still need other masses to permit eventual
launch vehicle choice
mwet or mloaded   mdry  m propellant
minjected  mwet  mkick
mboost  minjected  madapter
• mkick is apogee kick motor – if needed
• madapter counts against booster performance
#s
• Need to include margin
Spacecraft Design and Sizing
S/C Budgets
• For top-down designs, allocate so much of a
quantity or capability to each subsystem
• Types of budgets
–
–
–
–
–
–
–
–
Mass
Power
Communication bandwidth
Volume
Reliability
Pointing error
Cost
Schedule, etc
Spacecraft Design and Sizing
Mass Budget
• See previous navigation S/C example
→ Now add mass margin into calculation
mdry w / m arg in  mP / L  mbus  mm arg in

mdry
w / o m arg in
• Margin covers the uncertainty in our
estimates
– Typical range from 5% to 25%
– Larger margin for new S/C, or earlier in design
phase
– Smaller margin for known S/C, or as design
progresses
Spacecraft Design and Sizing
Preparing a Power Budget
Spacecraft Design and Sizing
Typical Power Consumption by Module or
Subsystem
Spacecraft Design and Sizing
Propellant Budget
• List v’s
• Use ideal rocket equation to convert  v to
propellant mass
 mi
v  I sp g 0 ln 
m
 f




Spacecraft Design and Sizing
Propellant Budget
Spacecraft Design and Sizing
Estimating Spacecraft Equipment Compartment
Dimensions