One of the more interesting modules that was originally going to be part of ISS was the Japanese-built Centrifuge Accomodations Module (CAM). The CAM was designed to provide the facilities for testing the impact of reduced and hypergravity–over a range of 1 milligee up to 2 gees of acceleration–on various biological specimens. Tests on these specimens, up to and including rats, would give us valuable information on the impact of gravity levels we might encounter on other planetary surfaces than earth, as well as giving us some data on what levels of artificial gravity might be required to prevent the debilitating effects of microgravity on people.
ISS Centrifuge Accomodations Module (Credit: NASA and Wikipedia)
As I’ve discussed before on this blog, our knowledge of the impact of gravity levels other than microgravity and 1 gee are almost virtually nonexistant. We have billions of data points at 1 gee, and we have hundreds of data points in microgravity, but we have a few tantalizing hints from the six Apollo lunar landings–nowhere near enough data to make responsible projections. It may turn out that only a little bit of gravity can go a long way (if the negative effects are driven by fluid distribution in the body like I think it is), or it could turn out that even Martian gravity isn’t enough.
This is the kind of information we really need to learn if we’re ever going to be a spacefaring society, and CAM would have provided that data. Unfortunately, in 2005, the partially completed module was canceled, due to budget overruns and issues with trying to schedule a launch before the Shuttle was to be retired. The module has been sitting outside at a space center in Japan ever since.
At the time, that may have sounded like a reasonable decision, but now that it is looking like ISS won’t be splashed in 2015/2016, and with the new emphasis on manned deep space exploration, it would be nice if that decision could be undone. The Augustine Committee mentioned research on the impacts and mitigation of reduced gravity effects on the human body as one of the reasons for extending the ISS’s operations to 2020.
Unfortunately at this point the team has been disbanded for long enough, and the hardware exposed to the elements long enough that resuscitating the CAM is probably not in the cards. More importantly, like most other ISS modules, CAM was designed to be launched on the Space Shuttle. While it is possible to develop an adapter for EELVs that could allow ISS modules to be launched on them, such a system has yet to be funded. So for now, it looks like restarting the CAM project as originally formulated is probably a dead end.
So here’s my crazy idea. What about modifying a Dragon capsule to house the centrifuge experiment and its supporting equipment racks?
Dragon Berthed at ISS (Courtesy NASA and SpaceX)
Most of the volume in the CAM design was actually storage rack–10 of the 14 ISPRs in the module were set aside for storage, and only 4 were planned for science.  The actual centrifuge itself was about 2.5m in diameter, but not very thick. Looking at the Dragonlab datasheet, I wonder if it would be possible to make another copy of the centrifuge assembly itself and fly it as a payload on a DragonLab flight to ISS. Looking at the available volume, it looks like you could fit the centrifuge and possibly as many as 1-3 of the 4 payload racks that were originally slated for the science mission. I’d need to do a quick CAD model to see if the ISPRs would fit as-is, or if you’d need to go with some other science rack configuration. And such a setup wouldn’t have all the capabilities that the original CAM had, but it would give you some of the most important functionality. Also, being part of a reenterable spacecraft, there would be the benefit that you could bring the setup back to earth to repair, modify, and upgrade it from time to time.
Looking at the sizing, this might require a dedicated Dragon airframe for the project. The centrifuge assembly itself is too big to fit in the door in one piece! It might actually be necessary to build the capsule around the centrifuge. But there’s enough experimentation that would need to be done over the years, that it would probably make sense to do it that way. The duration of DragonLab missions are listed as up to 2 years. At that rate, you could do long-duration experiments, but still have the thing back down for maintenance, upgrades, and refitting frequently enough that it might allow you to make some design simplifications. Also, basing the CAM inside a Dragon capsule would mean that the team designing the science hardware could focus just on the experimental apparatus, instead of having to design a full spacecraft like the original CAM. That might save a lot of time and money compared to trying to complete the original CAM. Lastly, the Dragon capsule can be either docked to the station, or can serve as a freefloater, whichever makes more sense scientifically.
[Note: It might also, just barely fit with the Orbital Sciences Cygnus spacecraft. I don’t have internal dimensions for that, but judging from the external dimensions, there’s a chance. If someone who has data on what the layout of the usable volume for Cygnus is, that would be helpful.]
By offloading all of the work other than the apparatus itself, and by using a relatively inexpensive launcher, this could be a way for international partners to contribute. Either Japan could provide the apparatus, or if they’re not interested, this could be a way to involve India or China in the ISS program. It would also be something well within the capabilities of Canada or the UK as well.
In fact, it might even be possible to do this entirely as a commercial venture or as a privately funded not-for-profit venture. A commercial venture would be risky, since you would need some sort of guarantee that someone would actually pay for the data.   A not-for-profit with a wealthy benefactor who would be willing to subsidize the experiment, (much as has been done for many university science labs, telescopes, and other not-for-profit scientific facilities) might make more sense. Imagine the Stanford or Caltech or MIT Orbital Centrifuge Lab, or the Bill and Melinda Gates Orbital Centrifuge…
As far as a spacefaring society is concerned, CAM would’ve been one of the most useful experimental hardware on the ISS. It may be too late to restart the CAM module as originally conceived, but Dragon–if successful–may provide another chance at making the ISS truly relevant.
Jonathan Goff
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Good idea. The centrifuge could also go into a Bigelow module. That module could simulate an interplanetary journey by parking it at L1 or L2.
Yeah, since the module in this case would be in the form of a movable spacecraft, you could attach it to whatever you want (or just use it as a free-flyer).
~Jon
Brillinat idea Jon!
It’s not too difficult to imagine the advantages that an entire space station composed of many Dragon capsules docked to a ‘backbone’ could deliver: Flyback capability, extensive re-configurability, and cost-savings from basing many modules on the same spaceframe — as opposed to one-off custom modules.
This idea seems so obvious that it surely must have already been proposed elsewhere.
If Dragons are eventually produced in the same numbers as Soyuz capsules, that would lead to greater savings compared to those of building just three US Nodes or MPLMs, both of which rely on a very expensive launch vehicle. Furthermore consider that if the Soyuz and its docking mechanism were designed such that the orbital module could remain at the station after the separation of the re-entry module, the ISS would have a lot more habitable volume by now (provided there were sufficiently many attachment points). A space station built from modules essentially identical to the very vehicles used to visit the station might simplify it’s overall design.
Good topic Jon. For an organization that basically exists to make humans live in space, they spend surprisingly little money and effort making that happen. You’d think someone in power would say hey guys, maybe we should spend less money on bigger rockets and space ships, and figure out how to not die in space because we cant grow food or survive radiation. Or live there without turning into jellyfish. Or have sex without risking creating an abnormal baby. Or operate on someone who is hurt.
Even the last MPLM PMM could be modified with some sort of centrifuge before it is sent up. Only the slow speed of unmotivated government workers means it won’t happen.
Jesse,
To be fair, there are some real costs to modularity. Something like this might make sense for an important experimental apparatus that can’t be done as a regular module anymore, but the overhead of dealing with tons of tiny capsules shouldn’t be overlooked.
~Jon
Ralph,
To be fair, this option has only really been available for a short while. Actually, to be technically accurate, it isn’t even really available yet. SpaceX still has to prove out the Dragon (or OSC prove out the Cygnus) before this is feasible. Before that happens, the difficulty of getting a small module up without the shuttle, and with the non-existence of off-the-shelf tugs, makes it a lot harder to do something like this. It isn’t that NASA’s lazy, some of this stuff really takes time. It’s just that a new opportunity is on the horizon that might allow us to fix the mistake of canceling CAM.
~Jon
Launch the centrifuge module on an Atlas or HTV using the Cygnus spacecraft for the berthing. It’d be a lot easier to change the Cygnus pressure vessel diameter than to modify the Dragon.
Of the spacecraft available in the near future, Dragon seems the least well suited for this. The HTV might be a better option. How heavy was the centrifuge, and could the H-2A launch it? Could the HTV be modified for long-duration flight?
FYI, I meant to write H-II, not HTV, in my previous post.
From what I understand one of the issues with science on the ISS is the vibration environment. Would it be practical to load experiments into a Dragon or Cygnus, then use the arm to place it back into it’s “safe” area, where the spacecraft has to stop to be captured?
Then you could do fragile experiments, without the vibration issues of the ISS. Once the experiment is done, the space craft could be recaptured. Any vehicle used this way would still have it’s fuel if for some reason it drifted.
A full Dragon capsule contains some very expensive systems that a space station module does nor need. These include independent power, a full oxygen handling sub-system, guidance system, heat shield, star tracker and others.
I wonder if it would be worthwhile separating the systems just used during launch and rendezvous into a reusable section that returns to the Earth after docking?
Another option: European ATV. There is some discussion of linking several together for an ad hoc space station. I don’t know if the could be upgraded for a longer on station life of two years however.
Using a Bigelow module would be interesting if we, or our partners, could manage the muster of purchasing a module.
my 0.5 cents….
J
I have some concerns about testing on very small diameter centrifuges and then extrapolating to humans – due to the Coriolis forces, .
I have heard it said that above a few rpm people become disoriented, could this be adapted to? For people to live comfortably in space at one gravity might require a centrifuge a couple of kilometers in diameter. This suggests two modules with a tether between them, more modules can then be added incrementally (bootstrapped).
Should an experimental centrifuge preferably be designed around a long tether? Perhaps one that could be varied in length, so as to be able to vary Coriolis forces?
@Pete
We probably want the forces on the heat and toes to be within 1% of each other. For a 2 metre man (6’6″).
x * 1% = 2 giving x = 2 * 100/1 = 200 metres
For a small (5 cm = 0.05 m) animal
y = 0.05 * 100/1 = 5 metres
The main questions to answer are whether .38G Mars gravity or .16G Lunar gravity allow relatively normal mammalian living and development. How do we answer that?
Jon’s proposal is very similar to my own solution but with regard to the Mars Gravity BioSat instead of the CAM. Space biology has always been hard to fully fund regardless of scientific importance or funding source. The most successful missions like this were the old Soviet Bion flights. The suggestion of HTV or other cargo tug also has interesting possibilities. The flight of a Mars-gravity rodent mission needs to have a high level of public engagement. How to bring the public into the mission?
Dr. Thaddeus Fulford-Jones wrote his PhD thesis on the habitation section of the BioSat. In it he describes a centrifuge with a very short spin and how to account for it. MIT tested a prototype on a parabolic aircraft in 2008. They pushed the concept far beyond the original Mars Society proposal. Their design is very rigorous science using mice sequestered in individual pods.
What CAM equipment still exists? Was the centrifuge built? Where is it or similar hardware? Reusing grounded hardware might be possible.
Nice idea but is it really a requirement that one can’t build the apparatus from pieces that fit through the hatch? And since the apparatus will be new anyway one can scale the completed centrifuge to fit the max internal diameter without having to use a special version of the vehicle.
Pete you might find this page interesting:
http://www.artificial-gravity.com/sw/SpinCalc/SpinCalc.htm
About half a kilometer diameter should be a conservative “minimum” option for 1g assuming the Earth-based testing is truly relevant. It might not be, it could be that it’s far too conservative, particularly because people adapted fairly well in the Earth-based testing.
Tethers –especially long ones– seem to have issues in space, needs some cheap thorough testing to be validated before being used on expensive stuff imho.
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