KSP Community CubeSat

[Nicholander]

Designing/Engineering it first, but K^2 hasn't finished the sim yet.

[astropapi1]

Sorry, make that 4 books, here's his page:

http://www.oreilly.com/pub/au/4997

Someone willing to buy it?

(and yeah, we need to get building soon, or at least designing)

Four dollars per book? hnnnnnnnnng! I wish I could get a credit card.

[xenomorph555]

Hi guys, I haven't checked out this thread in ages. I was here when it started but I didn't think it would come to anything, but surprisingly it seems to have become quite popular.

May I ask what progress has been made on this project.

[henryrasia]

Hey xenomorph555, I'm glad you joined us!

In what comes to progress, we've bounced ideas back and forth and have generally agreed that for a first mission (emphasis on first) will be a 1U cubesat spinning for 3 weeks growing moss in simulated Moon and/or Mars gravity. Details are vague (much more than I'd like, let's get a shared google doc up!)

Concrete progress? None at all

(to be fair though, there's a mod out there for KSP with 1U cubesats, marketting I guess?)

[Bobnova]

Given that nobody has landed anything on Phobos, survivable landing or impactor, I think that hitting Phobos with something is a perfect goal.

Any engineers here that can design something convincing enough to get someone (Elon Musk I'm looking at you) to throw half a million bucks at it?

Can you imagine the look on people's faces if a group of KSP players manage to land something safely on Phobos for less than a million bucks? That'd be incredible.

[NERVAfan]

Sorry, make that 4 books, here's his page:

http://www.oreilly.com/pub/au/4997

Someone willing to buy it?

Yes. I'll see what I can find that's relevant.

[Nicholander]

Bobnova, our first mission will be a 1U CubeSat that will be in LEO that will have artificial sub-gravity. It will have that sub-gravity by spinning, and I say "Sub-gravity" Because it will only spin to Mars and Lunar gravities. There will be moss in a pressurized area in half of the CubeSat, and we will see how it grows, develops and reacts to the Lunar and Martian gravities.

[henryrasia]

How can we do both Mars and Moon gravities in a 1U cubesat, though? Any tiny change in position, curvature of petri dishes, and rotation speed will make huge differences in artificial gravity at that small scale.

[astropapi1]

How can we do both Mars and Moon gravities in a 1U cubesat, though? Any tiny change in position, curvature of petri dishes, and rotation speed will make huge differences in artificial gravity at that small scale.

I don't think making the cubesat rotate at such speeds is a good idea. Some kind of counterweight would be far better IMO. Here's a little graphic I made in Paint.NET just to show how I think it could work:

[xenomorph555]

Thanks for telling me about the project guys .

Unfortunately I doubt I could help that much although I do know a bit about engineering and my granddad owns a large amount of engineering machines and machining tools (he used to work as an engineer and freelance engineer before he retired). I guess I could maybe build something simple, like the counter weight (assuming it's literally a pure block of metal with a few specifications).

I am also training at college to become a coder (and other IT things) so in the future I could also create software for the satellite (25% maybe, 75% probably not) but at the moment I can't do much for you since I started in September.

Also Astropapi1 the probe will need an RCT (only 1 needed) and a tank for fuel (I recommend high concentration hydrogen peroxide for RCT fuel).

I also recommend 2 cables (made of steel) for the connector between probe and counterweight, just to be safe so it doesn't snap.

[Nicholander]

We don't need fuel (I suppose you mean RCS), was we will put a magnetorquer instead, and honestly, I don't think we need a counter weight, I think it is stable spinning at Mars gravity. Feel free to correct me, though.

[xenomorph555]

Ah yes that would work

[Nicholander]

Which do you mean? The magnetorquer or the Mars gravity spin stability?

[Bobnova]

Bobnova, our first mission will be a 1U CubeSat that will be in LEO that will have artificial sub-gravity. It will have that sub-gravity by spinning, and I say "Sub-gravity" Because it will only spin to Mars and Lunar gravities. There will be moss in a pressurized area in half of the CubeSat, and we will see how it grows, develops and reacts to the Lunar and Martian gravities.

I like that idea.

Has anybody done the calculations to see how fast it'll need to spin to simulate those gravities? I'm curious how fast it'd have to spin.

[NERVAfan]

I like that idea.

Has anybody done the calculations to see how fast it'll need to spin to simulate those gravities? I'm curious how fast it'd have to spin.

Well, a 1U cubesat is a 10cm cube.

This artificial gravity calculator (http://www.artificial-gravity.com/sw/SpinCalc/SpinCalc.htm) suggests 53.5 rotations per minute to produce 0.16 g with a radius of 0.05 m. That's less than one rotation per second; doesn't sound TOO insane.

Well, we can't do both at once in the same cubesat*. We could switch partway through, but this experiment is probably sharply time-limited due to orbital decay. Maybe we should just do Moon gravity, and if we have enough funding follow it up with a Mars gravity "Kerbsat-2" or whatever?

*well, I think technically a rotating object will have 0 rotational gravity at the axis of rotation and maximum at the edge, so yes, you can have different rotational g's in the same spacecraft. However, that sounds really ambitious for something this small.

For 0.38 g (Mars) I get 82.4 rotations per minute with the same calculator.

[henryrasia]

My issue with the experiment in a 1U cubesat is that the divergences in g-forces experienced will vary greatly with very little change in position. For instance, using that calculator, and assuming the moss grows on a petri dish that has, say, 5 mm of "dirt" (I know it won't be actual dirt but I forget the name of the gel) The difference between the top (radius 0.045 m) and the bottom (0.05 m) is between 0.34 and 0.38 respectively. The divergence is then of 0.04 g, or 0.392 m/s^2. In comparison the variation of gravity on Earth is at most 0.052 m/s^2 (source: http://en.wikipedia.org/wiki/Gravity_of_Earth don't judge me). Is this acceptable? I wouldn't think so.

Added to that, the fact that the centripetal force will be circular, a flat petri dish will have even greater variances between its center and its sides, as well as the direction being crooked. A solution would be to have a curved petri dish, which I think is feasible, but we'd have to have it custom made. On the other hand, if it is custom made we can add stuff like passive temperature control systems and sealing it against vacuum with everything already inside.

A solution to both these problems would be using a larger cubesat (2U or 3U, maybe even more), but that'd be expensive and wasting resources (unless we made it do many trials at once, since it's bigger anyways). Another would be a deployable counterweigh, which could be streched as far as we need it to. I don't see, however, that working. Can anyone do some math on the rotation of a cubesat with strings attached to a weigh?

Edited October 10, 2014 by henryrasia

[Bobnova]

That actually sounds like a really interesting experiment to observe, and one that will be relevant if we start trying to grow plants on a space station that is spun for "gravity".

[NERVAfan]

My issue with the experiment in a 1U cubesat is that the divergences in g-forces experienced will vary greatly with very little change in position. For instance, using that calculator, and assuming the moss grows on a petri dish that has, say, 5 mm of "dirt" (I know it won't be actual dirt but I forget the name of the gel)

Given that Mazon Del was talking about the entire petri dish being 5-10 mm tall, the phytoagar might be thinner than that.

The difference between the top (radius 0.045 m) and the bottom (0.05 m) is between 0.34 and 0.38 respectively. The divergence is then of 0.04 g, or 0.392 m/s^2. In comparison the variation of gravity on Earth is at most 0.052 m/s^2 (source: http://en.wikipedia.org/wiki/Gravity_of_Earth don't judge me). Is this acceptable? I wouldn't think so.

Well, it's still a much better approximation of lunar/Martian gravity than you can get on Earth, so for a first experiment, yes, I think it's quite acceptable.

If this goes well and we get more funding we can do a later experiment with a 3U which is spun so the long axis is the spinning diameter, if we want to.

EDIT: also, I think the gravity difference will be less at Lunar gravity, and since we really won't have time to test 2 different gravity levels (due to orbital decay of the satellite) and get much data for each one, I think we should just stick to Lunar.

[dharak1]

I agree that we should stick to lunar. Less power needed to get the cubesat up to speed and it's much more likely to actually have useful data because the Moon is so much closer than Mars and is more likely to be used as a trial run for food growth.

[Nicholander]

Seriously, we should also do Mars gravity! I've already explained how we'll do both gravities before, so I don't need to say it again for the 5th time.

[henryrasia]

Sorry, wrong data, here's a recalculation:

The divergence in the phytoagar (thanks NERVAfan) would be of 0.392 m/s^2 while the maximum divergence on Earth is of 0.0698 m/s^2, maximum (between peak of Nevado Huascaran and surface of Arctic Ocean). Still that's more than 5 times the divergence! And while I don't know the physics of it (does anyone here?) the difference between center and sides of the petri dish.

Also, less than 5 mm? Any biologist here to confirm this is possible?

Edited October 10, 2014 by henryrasia

[henryrasia]

Here, I've created a google doc to get our ideas down, the link allows commenting:

https://docs.google.com/document/d/1jR2B_M67cITTBtV_PDMoioVQp3bnCTR85ecQeVKmpWI/edit?usp=sharing

This is by no way final, ANY suggestions are welcome!

[livefree75]

Name suggestion: KSPRL (KSP Real Life) (sorry if that is somewhat lame)

[NERVAfan]

I think we may have serious thermal control issues:

[in LEO] you can expect a floating object to experience a range from -160 C to 200 C (as a rough estimate). By clever thermal design â€â€described below, and using tricks like rotating your craft to distribute heat more evenly and using insulation, you can cut this to a range of -100 C to 100 C. This is still outside the range most off-the-shelf electronics can handle. If you minimize your radiative properties (choosing white or reflecting casings)

to reduce both heating due to the sun and re-radiating that heat in the dark, and you assume there is some on-board heating of your components due to being in use, you can achieve a temperature range of -30 to 90 degrees as typical.

Assuming a 10cm x 10cm Cubesat profile, that means it gets about 14 Watts of direct heating on its surface [in the sunlight]

So it sounds like we are going to need MUCH more thermal control than the "typical" cubesat, since we probably need to keep the moss between -- at the most -- 0 and 25 C, and probably between something like 10-25.

[Sky_walker]

Until then, however, we're starting with a LEO cubesat with an actual scientific experiment so we can make the most out of it AND maybe hitch a free ride from NASA, cutting ~$60k from the costs.

Well then, you have a problem. Or two problems, actually.

First one being that the experiment you propose was already done in space, including by far more in-depth and interesting analysis than anything you proposed here. It was done more than once, on far more interesting topics than just "growth". One interesting fact here: ill-fated Columbia (yes, the one) took moss in Petri dishes analyzing it's growth in space: http://www.sciencedaily.com/releases/2003/01/030115065325.htm (if you really want to know - moss didn't survive).

So I very much doubt that sending moss in space and snapping some photos of it would in any way increase your chances of having a free flight. You don't even have any idea of which aspect of moss you'd like to study, not to mention anyone with education background in biology to at least make you some ground work on a topic. What you are doing is not an actual scientific experiment, it's just an excuse to send a cubesat into space. An excuse that might not really work well, as your project in it's current form will most likely be perceived as nothing more than a private mexican company wanting to pull off PR stunt for US taxpayer dollars (yea, sounds harsh, but people judging your project won't do you any favors either)

And secondly - that excuse is very fault-prone. You rely on many very crucial components working in extreme environment with no experience working with any of them. I'm not really into the whole cubesat hobby thing, but I heard about simpler and more reliable cubesat-based experiments failing (read about PW-Sat and it's failed solar tail experiment). You should really read stuff about KISS rule.