KSP Community CubeSat

[Lunniy Korabl]

Avatar as requested! Tweaked it to be more legible that a direct resize of the patch.

[henryrasia]

Awesome! Already using it.

[Nicholander]

Do we have to use the new avatar? I'm pretty happy with the one I already have.

[henryrasia]

You don't have to do anything. I put mine because I didn't have any. On the other hand promotion is good, so the signatures definitely will help. Also, I changed my "title" to "Cubesat Project Member", again because I was just using the default one.

What we really have to do is finish up a rough preliminary design design REAL soon. Maybe I can get concept sketches done, but don't rely on this and definitely do not expect quality drawings...

[Treldon]

I did a bit or searching about the cubesat our university sent up (MaSat-1)

Couldn't find schematics, but here is the main site, and here is a brief description of it (might have some useful info)

Quick rundown:

- it was launched in 2012, has been up for almost 3 years now, should deorbit sometimes next year

- it uses magnetic torquers for stabilization

- input power is 1.2-2.2 W (power is supplied by solar panels on all 6 sides)

- communication is via Half-duplex on 435-438 MHz with >1200 bit/s, the transmitter is 100/400mW

- development time 4+ years

- cost of launch ~$100.000 (launched through Arianespace), cost of building ~$150.000

OFF: for a bit of flavor

[henryrasia]

Damn, 4+ years of development and $150k for building only...

If we ever are going to do this we're going to seriously break some records in development time and building costs... As well as professional qualification (or lack thereof ). But maybe we can make it cheap enough (to build) it will be the most inefficient space mission ever! (only one petri dish, and a camera)

Good things we're crowdsourcing development (that's us! ), funding (kickstarter), tracking (amateur radio stations), and probably the whole mission (in the event it outlives its usefulness but is still functional). Best business strategy evah!

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Just to be clear now, we're discussing power consumption, solar panel configuration, and battery specs/regimes, right?

Edited November 18, 2014 by henryrasia

[Treldon]

Luckily we don't have to make our own up to the same standards.

The MaSat is pretty much the official space program of a (small, but technically savvy) european country, built in its largest university. It must work.

Ours is a hobby project built in a garage. As long as it does anything we plan it for, Mission Accomplished

[Mazon Del]

While I hesitate to set the bar too low, if all we manage to do is get a hunk of metal into orbit with KSP written on the side, Mission Accomplished. Ideally though we would of course like the hunk of metal to DO something.

[Nicholander]

Wait, WHAT!?!?! How the heck do you end up using $150,000 to make 1 little CubeSat?!? I mean like, ArduSat asked for $35,000, and SkyCube's goal was $82,500. So I have no idea how they ended up using $150,000, beats me.

[Mazon Del]

Depends on what they were actually bringing up. If they used rad-hardened electronics and they were bringing a lot of electronics, that number is pretty believable. Especially if they went through some crazy quality controls on the ground.

[Engineer of Stuff]

If you guys want some advertising, I could put the project logo in my signature.

[Nicholander]

Still, I don't think that we need that much money to just build the CubeSat.

[LvL]

Yeah. I'm with you there

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On another note, I Possibly may be able to get my hands on some of the moss, and do some basic testing on it... but what tests do we need to do on it?

[LordQ]

Hey guys, sorry I've.not been around. I've just finished my final semester of university, so I've been incredibly busy. I was wondering btw whether we have an IM group we can use to communicate and do work in real time? I think if we got one, our productivity would probably increase. I mainly use Skype, so I would prefer that if you guys are alright with it. My Skype id is lord..q, so feel free to add me.

I've just done a course on the basics of spacecraft engineering, so hopefully I'll be able to make some solid contributions. To add to that, I'd probably say that I'm most confident with structures, and I have some CAD expertise.

[NERVAfan]

Yeah, I don't think $150,000 is at all typical for building a cubesat.

Since rear face will always be shade-facing, I propose using it as a radiator by painting it black and insulating it from the rest of the sat, except via a thermocouple. We can then use the later to control heat flow out of the craft. On the day side, we'll probably be wasting some power to actively push heat to the radiator panel, and on the night side, cut that flow down. This isn't something that most cubesats have to worry about, but it might be critical for a bio experiment. I'll do estimates on expected heat flows later.

Yes. Thermal control will be absolutely critical. Do you think this radiator will be enough to keep temperatures within a tolerable range in sunlight? We might need a heater as well...

[K^2]

Yes. Thermal control will be absolutely critical. Do you think this radiator will be enough to keep temperatures within a tolerable range in sunlight? We might need a heater as well...

You can always use magnetotorquers for heat in the worst case. It's just as efficient as any other electric heater.

[dharak1]

Wouldn't we need to run lots of current through them to do that? Could we supply the power for that?

[K^2]

Possibly, but that's kind of irrelevant. Can't heat at more than 100% efficiency. We either have enough power, or we don't. Dedicated heaters won't make a difference.

[NERVAfan]

1. 4 side pannels open 90°. 5 panels total exposed to direct Sun light. 10W production. Rotation axis connects centers of front and rear faces.
   Advantages: Lots of power.
   Drawbacks: Mechanical complexity.
   
2. 3 "front" faces covered. 3 panels at 58% exposure. 3.5W production. Rotation axis connects opposite corners.
   Advantages: Best usage with fixed geometry.
   Drawback: Trying to pack everything around a diagonal.
   
3. 4 side panels covered. 1 to 2 panels at 0% to 100% exposure. 2.5W production. Rotation axis connects centers of opposite faces and is perpendicular to Sun light.
   Advantages: Standard axis.
   Drawbacks: Very poor cost efficiency and nightmare to control.
   
4. Front panel only. 1 pannel exposed to direct Sun light. 2W production. Rotation axis connects centers of front and rear faces.
   Advantages: Simple. Cost-efficient.
   Drawbacks: 2W. That's 1W averaged over night/day, which barelly keeps us operational.

How will we decide which solar setup we go with? Are we going to vote? I think we need to decide soon since the power available will determine lots of other things.

Also, are we going to lose enough heat through the radiator panel to keep the moss alive in sunlight?

[henryrasia]

If we choose components based on power we're going to be severely limited by our own doing. We need to first determine "tiers" of power consumption to then decide on solar panels. This way we can eventually make "stretch goals" to get the extra power and components in.

And no, we shouldn't vote because this is a mission-critical decision, we should find the best option and reach consensus. So what's the power requirement?

[heng]

correct me if i'm wrong, but probably one of the most power consuming tasks would be thermal stability. could it a) be possible and/or cost effective (weight/mass consideration against power usage) to use a 'water' (or something) cooling system?

the thing i have in mind is as follows:

you have a collector, exposed to sunlight - basically just a black, heat conducting surface - and opposite, exposed to shadows, a radiator. could be identical, which would simplify construction. heat is distributed throughout the cube via tubes - aluminium [sic!] comes to mind - and a small pump. obviously water is not the medium of choice, but maybe it would work with gaseous nitrogen or liquid freon or similar? yes, no gravity, reduced convection, it has to be active.(*)

the key point are adjustable covers over the collector/radiator. if it is too warm, cover the collector. if it is too cool, cover the radiator. as simple as that.

pro: no expensive, complicated electric heating, adjustable radiators prevent cooling out too fast.

cons: i have no engineering background whatsoever, this is just a crazy idea in a crazy mind (and now a crazy forum ;-))

PS: you guys all have seen the Cubli flywheel?

is this a usable concept for attitude control? or too complicated for a cubesat?

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(*): on second thought, the thing has to be pressurized internally anyway, right? so maybe heating the air inside would suffice?

Edited November 20, 2014 by heng

[Nicholander]

Cubli? That is only useful for moving around on the surface of a planet, so no. We're sticking with the magnetotorquers

[henryrasia]

Those are some seriously OP reaction wheels for our purposes 0.o

But yeah, magnetorquers should do the trick, at least in LEO. Also, can they serve as heaters? Wouldn't that be too much wear and tear? Especially if we build it ourselves...

So, how's power consumption looking? I can see burst usage vs continuous usage, maybe even a sleep regime? We'll have a transmitter, MCU, camera, and LEDs that'll have consumption peaks and thermal control, that'll be continuous. How much will each of these take continuously? Because peaks can be dealt with a battery, as long as it recharges quickly. From these numbers well get a solar panel configuration, not the other way around.

[Nicholander]

LEDs? I thought we were going to have it be pitch black inside the pressurized area, and see what's going on using night vision. (And we would use something else to substitute photosynthesis for the plants)

[henryrasia]

That's why I put it into burst use. We're only going to flash the moss for pictures, which I don't think will change it's photosynthesis. It's just that I don't know what kind of data we're looking for, and so visible light would be best. Mazon Del should know better, though.