Designing Space Science Experiments
Space is a very unusual environment, so the experiments that fly in space
face some unusual engineering challenges. This document gives you an overview
and introduction to some of these challenges. The aim is to help scientists who
want to propose an experiment understand the environment and engineering issues
so we accelerate the learning curve.
I'm writing this document based on my understanding of space flight and space
science, and the exposure I've had to some of the Soyuz, Mir and ISS science
equipment, but I'm not a space engineer. Fortunately we have access to a
phenomenal team of very experienced space engineers - possibly the most
experienced team in the world - in the form of the Energia corporation. As part
of my flight contract we have included the requirement that Energia will assist
with the design of our science experiments. They have more time in space than
any other country or company.
But we don't want to waste time, so this document serves to brief you on the
fundamentals so that you aren't surprised at what can and what cannot be done.
Character of Space Science Equipment
Space science equipment doesn't look very impressive. It looks old-fashioned,
and downright simple. That's because it is! Contrary to popular belief, the
latest and greatest stuff doesn't often fly in space. Because space is a very
tough environment, and because it's so expensive, and because it takes years to
design the equipment, and because everything has to be guaranteed to work for
many years (15-25) without replacement or repair, the equipment is engineered to
be robust, light, SIMPLE, predictable, and accurate.
If you've every worked with cutting edge equipment you'll appreciate this.
Think about it! The latest and greatest stuff is usually fragile, temperamental,
leaky, needs specialists just to keep it working, doesn't last very well, breaks
in unpredictable places and unpredictable ways, and usually isn't particularly
compact. So space equipment is extremely well engineered, extremely expensive,
but usually not very impressive. Don't be surprised when you read the specs of
the equipment that's already there if it doesn't measure the latest gee-whiz
parameter or offer the most up-to-date facilities.
The point of space science is to explore qualities of materials that are
unique to space. ANYTHING that CAN be done on earth should be done on earth.
ONLY stuff that uses the unique properties of space makes sense to do in space.
It costs around $50,000 per kilogram to put anything into orbit. That's
just the launch! It costs a lot more to keep it there during the lifetime of
the equipment. There are fundamental limits on the amount of mass that a
shuttle or Soyuz or Progress can carry, and the ways that mass can be
distributed. Experiment equipment should be as light as possible.
The ISS and all the launch craft are very small. Soyuz can barely fit three
adults, ISS is pretty cramped too. Every cubic centimeter of space is
accounted for. Equipment needs to be as compact as possible.
Astronauts work flat out. Every minute in the day is accounted for and
planned in advance to the greatest extent possible. Because human time in
space is so limited and so expensive the experiments are designed to work with
minimal human intervention. An astronaut might switch it on and switch it off.
But try to avoid having to have an experiment that needs constant observation.
The astronauts tend to be generalists rather than specialists, so experiments
need to be able to be operated by people who are new to the field. There's
time allocated to science training, but it's limited time since the astronauts
also have to handle all the space flight crew training in the lead-up to a
For example, say people want to observe the behavior of a microbe in
weightlessness. The astronauts might take up a sealed tube containing a
deep-frozen specimen. Once there, the astronaut would thaw the tube by
removing it from the freezer and store it in a specified place for a specified
time, then freeze it again by putting it back in the freezer. That's it. The
frozen sample is returned to earth and only THEN would the tube be opened up
and all the observation work done. The sealed tube makes it safer (nothing can
leak) and simpler (no interaction required).
Power is a big issue on the ISS and in space. The station has to carry it's
power station along with it. Equipment has to interface to the station power
supplies very carefully... you don't want to go tripping power supplies, or
potentially damaging other equipment that draws on the same source of power.
Ideally, if we design any equipment to fly to the ISS for a short duration
flight, it would carry its own source of power (windup? batteries ;-) and not
need this interfacing.
Space equipment has to survive the G-forces (very rapid acceleration causes
stresses) of launch and descent. In the Soyuz this can mean man G's (up to 12
in an emergency, but 5 is normal). There's lots of vibration and shudder too.
Space equipment might be subjected to jolts and bumps if there is a collision
between the station and another craft. And equipment might be banged into
other equipment during use. The equipment must be super-rugged and designed to
withstand these sorts of stresses.
Even more important, if there are any dangerous chemicals or biological
materials on board, these must be contained in such a way that they will not
become a problem if there is a catastrophic failure during launch or failure.
In other words, don't spray dangerous things around if the rocket blows up or
the capsule parachute doesn't deploy.
So space science equipment is very sturdy, very simple in its design.
Equipment that is sent to the station has to survive many years without
breaking. The station is designed to last 15 years... Mir was designed to last
5 but flew for 15. So the ISS might end up flying for longer than the planned
15 years... and the equipment is built to last. Knobs and dials are very
chunky and robust... they might be switched on or off every day for 15 years
and a failure would be extremely expensive and disruptive.
If something does break it is better to fix it in space than to have to
schedule a replacement or repair flight. So equipment is designed to make this
feasible if it is at all possible. Again, the astronauts aren't necessarily
specialists in the field, so it needs to be possible for them to fix as much
as possible without that specialized knowledge. That takes a tremendous amount
of careful thought during the design of the equipment.
Any space vehicle is a sealed unit - we hope. That means that any leak is
effectively trapped and has to be dealt with in place... one can't just open
the windows to air the place out. No air. So any leak of gas or fluids can
become a major problem. All the air in the station is recycled and there's a
limited supply of it, so a poisonous gas leak creates an immediate crisis. Any
corrosive liquid will float around until cleaned up.
So any equipment that will contain fluids has to be assessed for safety and
the effectiveness of its containment. The simpler and more robust, the better.
Almost anything could fly to space, but the containment strategy has to be
adequate for the substance, and the level of risk if something goes wrong
means that dangerous substances have to pass many years of analysis and
We hope that all goes well, but emergencies happen. Space equipment needs
to be able to behave predictably and safely during an emergency situation. For
example, if the capsule or station depressurized, the equipment should not
leak or explode or do anything else unexpected. When the station comes down to
earth eventually, the equipment inside it will burn up and should not release
very dangerous substances such as radioactive dust.