The ISS as an engineering test bed

Last week the Expedition 32 crew celebrated their successful spacewalk to repair a Main Bus Switching Unit outside ISS. This spacewalk followed one the week before that failed to complete the same task. Hundreds of people spent the days between the two EVAs building and testing tools and procedures and replanning the whole timeline to allow for the success that we had on September 5th. The optimist will celebrate the ingenuity and resolve of NASA to get the job done – the pessimist or cynic will lament all the time wasted on ISS maintenance when we should be doing science. Clearly, my pessimist (perhaps a strawman, I admit) is missing the point.

I often get frustrated trying to justify space exploration, and especially the ISS, to people that do not share my innate love of spaceflight. Most space enthusiasts – I’m sure many readers of my blog – know what I’m talking about. Much like skeptics debating young Earth creationists, we have a lot of practice and have developed some nice lists of great talking points (most effective when delivered by Neil DeGrasse Tyson). Nevertheless, people that aren’t impressed by spaceflight are still often hard to sway – even when you explain that spending on the space industry isn’t just launching money into space, but is investing in technology and business here on Earth. I’m going to make an argument about the value of the ISS here, but my argument already assumes you agree that spaceflight is worth it, and that we should eventually send humans to impressive destinations like the moon, asteroids, Mars, and the moons of Jupiter (so Lawrence Krauss will not be impressed). If you still need to be convinced that these things are worth it, then I send you to Carl Sagan.

What I want to point out to those that question the ISS as a useful step in humanity’s road to the stars is that it is about more than just crystal growth, microgravity fire, and spiders in space. ISS research is interesting, and has real returns, but to try to justify the scale and cost of the project over the last 3 decades by just the science being done is to miss the point. Of course, the fact that there are humans in orbit all day every day every year is a philosophical point that you can’t put a price on – maybe not enough of humanity knows about ISS for this fact to make an impact. But what I want to talk about is the engineering value of ISS. Do not be fooled by the people that want to convince you that ISS has us “stuck” in Low Earth Orbit (LEO). The technical ranks of the ISS program are filled with people that dream of Mars and see what we are doing now as a way to get there.

You can’t send people to Mars without making the spacecraft and its crew significantly more independent than the Apollo spacecraft or the ISS. With Apollo, you could always just run home if you have a problem (like we did on Apollo 13) and on ISS much of the system operations and troubleshooting is done by ground controllers in real time – not to mention the Soyuz can serve as an escape capsule in a pinch. On an interplanetary cruise, if your systems don’t work and work well, you’re dead. Scary and simple.

For instance, a Mars mission with our current life support technology would be dicey. ISS has the first attempt at a real closed loop life support system (we call it Regen ECLSS). It works, but we do a lot of maintenance on it, more than would be feasible on an interplanetary flight with no hope of new spare parts or tools. I think of the ISS as an ECLSS test bed for these future missions. I would expect the next generation of hardware to vastly improve on the ISS systems as a direct result of lessons learned. It makes the time and money spent troubleshooting the ISS systems worth it, although we don’t see those returns now.

As the ISS ages, more things will break as a matter of course. In the summer of 2010 we had to replace a cooling pump that had been running for years, followed by the decade old MBSU we fixed last week. Both of these repairs took 2 EVAs or more (the pump module took 3). We are going to quickly improve our techniques for doing these repairs while also getting better and better at spacewalks and learning lessons that will make the designs of these components better in their next iterations. Take a look at Wikipedia’s list of cumulative spacewalking records.

ISS repairs gain EVA experience

The MBSU repairs for Williams and the cooling pump for Wheelock have earned them a huge amount of EVA experience. We can only expect this trend to continue over the next decade of ISS operations. Certain repairs are expected and there are many working groups at NASA who are already preparing “next-worst-failure” plans for how we will tackle them. Hopefully no daring Bruce Willis style spacewalks will ever be needed in future missions, but it would be folly not to plan for needing to go EVA while on interplanetary cruise. When the ISS program ends (be it in 8, 15, or 20 years depending who you ask) we will be well prepared with a vast pool of experience from the Space Shuttle and ISS programs to press on to the future. To be sure, the Orion program is already taking our hard earned lessons into account.

When you also consider that ISS will surely be used for Mars analog missions and endurance spaceflights before it is done, it is clear that ISS is an important learning platform. Every generation wishes that it will be the one to go to Mars, so it is understandable that there is more disappointment lately than optimism. I am confident that when we do finally go we will know what we are doing, thanks in great part to lessons learned as the ISS ages.

Ad astra!

September 9, 2012 3:02 pm

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