A city in the sky:
A cheaper space station from Bigelow
Vocabulary
• BA-2100: A Bigelow module. Volume: 2,100 m3.
Weight: 100 mT. Crew: 16, Cost: $500M.
• BA-330: A Bigelow module. Volume: 330 m3. Weight:
25 mT. Crew: 6. Cost: $125M.
• Falcon Heavy: An expendable launch vehicle from
SpaceX. Payload: 53 mT. Cost: $150M.
• Propulsion Bus/Docking Node (PB/DN): A unit used
to reboost the space station due to orbital decay
coupled with a module that allows Bigelow modules
to be attached together. Weight: 17 mT. Cost: $75M.
• Space Launch System Block I-A (SLS I-A): An
expendable launch vehicle from NASA. Payload:
105 mT. Cost: $750M.
Narrative
To live and work and be productive in space, you
have to have a place to call home. While the Earth is
certainly a great place to go home to (free air! free
water! free - well, you get the point), it would become
very expensive indeed if every time you knocked off
your shift in space you took a ride back to Earth, and
then got up the next day to fly back into space again!
The obvious answer is to place your home, your city if
you will, in space.
Shopping around for what’s available to use to build
our city, we happily find Bigelow Aerospace, makers
of the famous BA-330 and BA-2100 space station
habitat modules (the names of the modules denote
the pressurized volume of each unit). These inflatable
modules go into space, where they, well, you know,
inflate. Astronauts then move into what is essentially a
balloon in space (aren’t all space modules really just
that?). Ah, but what a balloon!
Crew capsules can dock at either end, and power is
derived from solar panels, while excess heat is dumped
into the biting cold of space using radiators. It even has
windows! Home sweet home, indeed.
Analysis
To launch these excellent habitat modules into
For a more in-depth treatment of this high
school project by Joe Maness & Rich Holtzin
visit www.stemfortheclassroom.com.
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space, we obviously need a launch vehicle. Once
again, shopping around for what’s available to use
to launch our city we find two Expendable Launch
Vehicles (ELV). These rockets haven’t been built yet, but
so long as funding continues they will be one day. The
two ELVs are the SLS I-A and the Falcon Heavy.
Since the SLS I-A ELV can carry 105 mT into Low Earth
Orbit (LEO), and one BA-2100 weighs 100 mT, it can
carry only one unit at a time. We will call this the “BA2100 Stack.”
The Falcon Heavy ELV can lift 53 mT to LEO, and
each BA-330 weighs 25 mT, so it can carry 2 units at a
time (assuming, of course, that it could fit in a payload
shroud). We will call this the “BA-330 Stack.” The PB/DNs
each weigh 17 mT, so 3 units will fly on the Falcon Heavy
ELV to LEO. This will be called the “PB/DN Stack.”
BA-2100 Stack
• Cost: (1) SLS IA + (1) BA-2100 = $750M + $500M
= $1,250M
• Weight: (1) BA-2100 = (1) 100 mT = 100 mT
• Volume: (1) 2,100 m3 = 2,100 m3
• Crew: (1) 16 = 16 Astronauts
BA-330 Stack
• (1) Falcon Heavy + (2) BA-2100 = $150M
+ (2) $125M = $400M
• Weight: (2) BA-330 = (2) 25 mT = 50 mT
• Volume: (2) 330 m3 = 660 m3
• Crew: (2) 6 = 12 Astronauts
PB/DN Stack
• (1) Falcon Heavy + (3) PB/DN = $150M + (3) $75M
= $375M
• Weight: (3) 17 mT = 51 mT
So let’s build us a city in space, shall we? Hey, if
the high school students at The Learning Community
Charter School (www.tlcnm.net) in Albuquerque NM
can have fun with this, then so can we.
Example
The folks at Bigelow Aerospace have made it easy
for us: they’ve already designed a very nice space
station! It’s called the “Hercules Resupply Depot,” but
we’ll just call it “Home.” Thanks, Bigelow!
www.RocketSTEM.org