KSP Community Cubesat Project: The Experiment & Moss survival conditions, etc.

[NERVAfan]

TO attempt to make the huge (currently 189 page) KSP Community Cubesat project/thread more readable, Newt suggested we should create separate threads for different parts of the project.

So here we go.

(Introduction for those not familiar with the project: The current plan is for a 1U Cubesat (10cm x 10cm x 10cm, maximum mass 1.33kg) in Low Earth Orbit. The experiment will involve spinning the satellite to create centrifugal "artificial gravity" and observing the response of moss grown inside the satellite to low gravity levels. Funding will probably be by Kickstarter, but we need a good plan and design first.)

Original thread, which is currently mostly covering 3D models and how to place the parts within the Cubesat:

http://forum.kerbalspaceprogram.com/threads/86010-KSP-Community-CubeSat/

General project Google Doc:

https://docs.google.com/document/d/1jR2B_M67cITTBtV_PDMoioVQp3bnCTR85ecQeVKmpWI/edit

This thread is for discussing the experiment itself - the moss, the camera and sensors used to measure it and its growing conditions, the environmental control needed to keep it alive.

Mazon Del was discussing the experiment with an actual scientist who studies moss. The leading contender for a moss species to fly is Physcomitrella patens (Is that still correct?)

[Mazon Del]

I'm not 100% certain about that moss, I need to check my notes. I'll edit this response later once I get the answer.

Right now regardless of moss, the most important sensor for this experiment will be the camera(s). Minimum of one camera, ideally two from perpendicular angles (so we can observe vertical AND horizontal growth).

Required Sensors: Temperature.

Other sensors that would add great value to the project: Humidity, O2/CO2 detection, pressure.

The current main idea under discussion is to have a ring that holds the samples (either in sample capsules mounted on the ring, or in chambers that are part of the ring) inside of a pressurized volume with one camera pointing 'out' from the inside of the ring and another pointing 'across' the ring. The camera pointing 'across' the ring is the more important of the two, as it will provide us with vertical data about the gravitometric response of the moss (how it reacts to gravity). The horizontal data (from the camera inside the ring) is useful for the moss bred for horizontal gravitometric response, but we cannot guarantee without the vertical data that it isn't just following the flat plane of its container.

Also under discussion is the idea of having all sample containers be their own pressurized containers. However at this time I believe this will provide us with more trouble because most of the data we can get from non-visual sensors (the temperature, humidity, etc) will generally not be collected usefully.

One of the major points of this experiment is to see if the moss can sense gravity at the low levels being tested. About 0.1G (the moon) and about 0.3G (Mars). If the moss cannot determine which way is up in the 0.1G or 0.3G settings, this tells us important things for food production in space, as this means the plants will have greater difficulty living and growing correctly.

[Bunsen]

Thanks for the summary! I took a look at the cubesat thread many months ago, got frustrated with 75% of the comments being from people not reading the thread and posting the same crap that had been posted and answered a dozen times over, and gave up after about 20 pages. There's no way I'd survive slogging through nigh 200 pages of that. [edit: having glanced at the last couple pages of the enormothread, I notice that I kinda did that myself. Mea maxima culpa.]

Sensors for humidity, pressure, and O2 are all small, cheap, common, and consume extremely little power. I don't know about CO2 off the top of my head, but I think those are similarly easy. I would be concerned about temperature variation -- a 1U doesn't have a lot of thermal mass for its surface area, and its temperature can swing pretty wildly between sunlight and eclipse. I'd want to check that 90-something minute temperature cycling doesn't mess up the moss.

Otherwise, you're going to need to stabilize its temperature somehow -- I see two obvious options: (1) design the craft to give the sample chamber a natural average temperature below what you really want, insulate it well to slow down heat exchange, and provide heaters (you really don't want to deal with the power consumption of active cooling, which is why I suggest designing it to need heaters) or (2) use a phase-change thermal buffer (basically a capsule of wax chosen to have a melting point near your desired stable temperature) which would passively limit temperature swings, but would provide no direct control.

Temperature cycling becomes a non-issue if you can swing a sun-synchronous orbit, but there are far more launch opportunities to lower inclinations, and sun-sync orbits require some real attention to thermal management to avoid overheating things.

Edited December 17, 2014 by Bunsen

[Creature]

Also under discussion is the idea of having all sample containers be their own pressurized containers. However at this time I believe this will provide us with more trouble because most of the data we can get from non-visual sensors (the temperature, humidity, etc) will generally not be collected usefully.

Either way presents some pros and cons. Going with multiple pressurized containers you lower the risks of seal breaches. There are more possibilities for it, but the effect is dramatically reduced if it happens. However this shouldn't be an issue because the container needs to be tested and manufactured so well that breach is not even a real possibility. On that thought, one mission critical thing to consider is what sort of regulations the launch provider has for pressurized containers. It's probably doable with just one bar of air inside but it may affect the design so it should be cleared as soon as possible (unless someone already has?)

I've never cultured plants (unless growing chilies counts) but I'd imagine that atmospheric variables are a factor in growth. As a rule of thumb with biologicals is that you need to know everything. If there's no growth somewhere, it helps ruling out at least the most obvious factors.

On the other hand if you have shared atmosphere but you're actually studying individual growths, then if there's early and/or strong growth, can this affect the growth of others by affecting the shared atmosphere and could it be an issue?

Another issue is with temperature measurements. It would be good to measure it from the inside of the growth chamber so that you can tell what the true ambient temperature is, not to mention the gas sensors which need to be in contact with the atmosphere. Obviously due to weight considerations you can't do this with individual cells, the wiring alone would hog several percentages of the precious weight budget. Additionally you need to find a way to get the wiring through the chamber wall while keeping it airtight. This might cause some headache, especially with multiple chambers.

To me it seems that you can either choose isolated chambers if you don't necessarily need all that data from the sensors and free up some weight budget or choose shared chamber if you want that sensor data and the interference isn't an issue.

Or go with some kind of hybrid solution? Divide the chamber in two separated parts, both with their own heating element and sensors. This way you could keep the other half at low temp where the moss hibernates (guessing around 5 degrees celsius?) and keep the other half at growth temp at the first g-force level. Once the first experiment is finished, spin up to the second gravity condition and start heating the second block. This is of course supposing that hibernating moss starts growing in a reasonable timeframe. As a bonus you could see what happens to the first growth when changing the gravity.

One more thing popped into my mind. Was there a spesific reason this experiment is done with the cubesat instead of inside the ISS (apart from the coolness factor)? It would also be interesting if identical experiment was done aboard the ISS using a small centrifuge. That would be a valid control as the conditions inside the station don't change and if the satellite-based experiment performs identically, it would also double as a proof of concept for cubesat based experimenting.

[Mazon Del]

The regulations for pressurization of the cubesat said something that ends up being "no pressure vessel can contain more than 1.2 atmospheres of pressure" or something to that effect. However, this is only true of the sat while it is on board the vehicle. Technically once the cubesat is free, they don't really care what you do. With the future ground based testing, we'll be able to see how much (if any) pressure increase we get from the plant growth over our estimated time tables. It likely won't be much, mostly because the size of the plants is so small, but additionally we don't have the issues that the Mars One crew would have. In the MO situation, they are giving the plants water external to their environment, of which the oxygen ends up released into the room, slowly increasing the pressure. Considering that the plants will be utilizing the very light amount of water that is soaked up by the agar/sucrose, we most likely will not have to worry about this.

We could theoretically have two different chambers as you suggested, though that will increase the mechanical complexity quite a bit. Personally I really don't think that sealing the chamber is going to present much of a difficulty at all. Getting the data/power lines through is not an issue. Once we figure out what we need in terms of power/data lines, we can buy connectors rated for vacuum operations ('expensive' but only in the range of like $15-$20 expensive). Cut the precise hole, put the connector in place, secure it. It would come with vacuum rated O-Rings and such. I've had to do just a little bit of that in the past.

The big hatch ends up being the only 'difficult' part. But even then, it isn't THAT difficult. A nice large O-Ring, some bolts integrated into the structure of the sat, tighten those down nice and good. Bam!

As far as why we are doing this in a sat instead of the ISS, the ISS was supposed to get a module for this, but that didn't end up happening (it's in a parking lot somewhere). We are doing it for a cubesat because why not? If nothing else it could give us useful experience for when it comes time to send something out of Earth orbit in the far far future. It would be kind of funny for a blob of moss to be the furthest biological matter from Earth.

[sndrtj]

Hi there, Molecular Biologist/Bioinformatician here. P patens is probably indeed the species you want since it is the moss model organism (i.e. intensively studied). Furthermore, mosses come in two different shapes; a gametophyte type and a sporophyte type. The sporophyte is for sexual reproduction, but gametophytes grow significantly better so you would probably want to use a colony of gametophytes.

As other have said, I'd reckon temperature control is going to be a major issue. Humidity probably plays a far smaller role (P patents being native to temperate regions, which can be alternatingly wet and dry), but you probably want temperature to be as stable as possible. Futhermore, there's the issue of light; it seems that light is necessary for proper tip growth.

[henryrasia]

From what I recall the chosen moss was good because it grew in the dark, which is important because it's easier to seal the sat for constant pitch bblack than it is regulating lighting inside the sat (orbital day-night cycles aren't exactly natural). The imaging would be done with flashes once every so long (moss doesn't grow that quickly, so we'll do a timelapse).Furthermore all moss samples will be identical and used mainly for redundancy. Though if we could hibernate them individually then Creature's suggestion would be very valuable, observing different gravities discreetly as opposed to one following the other.

Finally, I don't even know of the ISS has tiny centrifuges. They definitely did experiments with plants before, but those have always been in 0 g, not in the 0-1 g range we're shooting for. BTW we chose this experiment exactly because no one has done it before and it's not so simple to be done on earth as opposed to space. And yeah, this is mostly to get the know-how of space exploration, which isn't really accessible to the public (not even hobbyists) right now. Our ultimate mission is to land something on Phobos (we'll figure out what exactly it would do there later ) just because it's cool.

" We choose to go to Phobos in this decade and do the other things, not because they are easy, but because they are hard, because that goal will serve to organize and measure the best of our energies and skills, because that challenge is one that we are willing to accept, one we are unwilling to postpone, and one which we intend to win, and the others, too."

[MBobrik]

I've got an important question about the moss spores. If we launch through ISS, the cruise will take a few days, during which the sat will be inactive in a cold dark container exposed to vacuum. Can the moss spores survive this ?

Can for example the initial succrose moss spore mixtute be desiccated and then reactivated after a few days/weeks by releasing a droplet of water onto it ?

Edited December 18, 2014 by MBobrik

[Moss]

I'm honoured that you guys chose to launch me into space. I promise I'll do you proud.

[Bunsen]

From what I recall the chosen moss was good because it grew in the dark, which is important because it's easier to seal the sat for constant pitch bblack than it is regulating lighting inside the sat (orbital day-night cycles aren't exactly natural).

Forgive me if this was also discussed, but I don't see "tiny encapsulated atmosphere" being compatible with "growing in the dark." If it grows in the dark, it must get its energy from metabolizing something, and that usually requires either taking oxygen, getting rid of carbon dioxide or something, or both. If you want an organism to grow for long in a small, closed atmosphere, you have to provide some continued energy input. Otherwise, there's going to be a pretty tight limit on how much interesting stuff can happen before the chemistry hits a wall.

[Newt]

It is generally decided that we are going to move this topic to a new forum, rather than try to clutter the Science Labs on KSP's site with our discussions on the cubesat. If people are interested to continue this conversation, I would suggest that you could head on over to this thread, on the new KSP Community Cubesat Forum, and comment there. Thanks.

Edited December 19, 2014 by Newt
updated link after domain change