KSP Community CubeSat

[K^2]

( A lot more discussion here: http://forums.mossat.org )

So, at the writing of this, the thread is nearing 150 pages of discussion. The poll is largely irrelevant to what was decided to be the first mission, but I can't remove it, so it stays. I'm going to post the rough outline of what we are working on. For a bit more details, some of the work is being organized in this document. Keep in mind, however, that it is very much WIP, and none of it is set in stone.

Mission Objectives

• To construct a 1U Cube Satellite that adheres to standards necessary for launch, and have it launched and deployed to a stable Low Earth Orbit.
  
• To establish regular communication with the satellite via ground station. Be able to receive data, including images, from satellite.
  
• To gather data from an experiment that has some value to the scientific community.

Standards

General standards for CubeSats are available from CubeSat.org, but stricter criteria are likely to be imposed by the launch provider, which is to be decided.

Standards of NASA's CubeSats Initiative can be referenced as a general guideline.

Communication

There are two main options for the on-board transceiver, both having amateur bands we can use.

• S Band - This is what people more conventionally think of when they think about communication with satellites. Unfortunately, all of the necessary hardware is insanely expensive. The ground station will also require a satellite dish to track the satellite as it passes overhead, which is very challenging to construct or very expensive to purchase. Either way, this option would require much better funding. The advantage is primarily in the data rate. If we want to be able to stream live video from the CubeSat, we have to go S Band.
  
• VHF - We would be limited to 200W on relevant bands, but this is sufficient to get the range we need. The hardware can literally be soldered together at home, and if we are worried about radiation, a VHF FM transceiver can be literally wired together with radio lamps that are rad hard by default. Cheap, reliable, and there are amateur radio operators using these bands all over the world that we might be able to ask for help if we lose the satellite. The disadvantage is that we'll be basically limited to a typical FM radio band, which will give us something like 50kbps - 100kbps. It's enough to beam down images, but we will not be able to do video.

Experiment

We are still working out details, but the most likely option is growing moss in hypogravity. A lot of experiments have been conducted on plant growth in hypergravity, and a number of experiments in microgravity have been conducted on the space stations. However, no experimental data is available for the 0g - 1g range. Certain mosses have very strong response to gravity, and there is interest in scientific community in obtaining some real data on that.

It wouldn't be a huge contribution, but it would be something entirely unique that will result in some publications. Unfortunately, none of the people actively involved in this program are experts in the field. Hopefully, that will change.

Hardware

• Frame - Commercial CubeSat frames are available, but very expensive for what they are. We are discussing possibility of custom tooled parts for the frame, but we need to make sure we can satisfy all testing requirements with these.
  
• Main Board - That will almost certainly have to be custom built, but fortunately, there are plenty of PCB printing services out there.
  
• CPU - There are a lot of options. The main limiting factors are cost vs ability to withstand radiation of LEO. If we can't afford it, off-the-shelf CPU/MCU will do, but rad-hard is preferable. Assuming we go with VHF option, which doesn't require a CPU capable of high data rate, I propose using 8051. First, because rad-hard versions are available for reasonable price, under $2k. Second, because garden variety of these is dirt cheap, and we can experiment with them as much as we like. Finally, they are easy to work with. There is a huge amount of development tools available, including C compilers and emulators. If we need to, a custom emulator can be written easily. Power consumption of just over 125mW is also a plus. The largest drawbacks is that it can only execute 1M instructions per second, limiting data rate it can directly beam to the ground station, and the fact that it can only address 64kB of memory. That's enough for everything but streaming video, though.
  
• Memory - Ideally, rad-hard stuff. The fact that we only need 64k with above is a plus, because that stuff also get very expensive. On the other hand, rad-hard memory isn't as critical as rad-hard CPU, so long as the code is written to take possible failures into account.
  
• Solar Panels - This is the place where we cannot go cheap. We will have to buy space-rated solar panels for a number of reasons. They are most exposed to solar radiation, they are a critical point of failure, and they can't shatter during ride to orbit. All of that adds up to panels designed specifically for space operations, and that means lots of money. Other than the launch, it is likely to end up the single most expensive part of the project.
  
• Batteries - LEO gives us 45 minutes of almost total darkness for every 45 minutes of sunlight. Battery must be capable of withstanding large temperature variations, frequent recharges, and still be able to power the satellite on the dark side. We will also most likely rely on the battery to provide power for the transmitter, since that's likely to draw way more power than solar panels can provide. It does seem, however, that we can find standard batteries for that, rather than reach for space-specific stuff. So while not exactly cheap, this should be relatively inexpensive.
  
• Navigation - We will need a GPS receiver on board. It needs to be unlocked to operate at LEO altitudes and velocity, but such units are available.
  
• Attitude Control - RCS is not really an option. Fortunately, we don't need to maneuver. Only adjust attitude. Magnetotorquers are available for that. Again, commercial units are unreasonably expensive, but I think we can handle coiling some wire. Mass distribution of the CubeSat will be designed so as to allow relatively complicated attitude adjustments. The CubeSat will constantly spin on one of the axes, which will allow for better stability, attitude adjustments via precession, and will provide small amount of artificial gravity for the experiment.
  
• Cooling/Heating - Some components are temperature-sensitive. We might need a thermoelectric cooler on board, attached to external radiators. Other than that, making sure that most of the sat is reflective should reduce temperature variations.
  
• Camera - It sure would be neat to get some pictures from up there. An external camera for cool shots would probably be a good idea. If sensible, an internal camera to watch over the experiment can also be added. It has been suggested that a microscope might be a good idea, which might be possible to swing. All of these will have to withstand radiation of space. Odds are, however, that we'll simply go for off-the-shelf versions and keep our fingers crossed. Typically, about a week of operation is to be expected from non rad-hard cameras, which should be sufficient to get a few cool pictures and get most of the relevant experiment data.
  
• Other Sensors - We can make use of accelerometers and light sensors to help hold/change attitude. Temperature sensors will probably need to be littered through the whole CubeSat to make sure we are aware of any problems early. Experiment will probably require a suit of its own sensors. (More precise temperature, pressure, humidity, O2, CO2, etc.)

Software

Almost everything has to be custom-written. I'm currently working on a simulation to help determine some of the requirements. In particular, these for navigation tolerances, mass distribution, amount of power we'll need for attitude control, and typical comm ranges to be expected. That simulation will also be used later to help develop software for the cubesat itself. If we are going with 8051, that will be coded on the very low level, with direct access to all the hardware on board. I will also work on software for tracking and communicating with the satellite, which we will try to make available to as many people as possible using amateur radio equipment.

Funding

Eventually, this will probably become a KickStarter project. We will need money to buy the parts, probably to pay for at least some of the testing, and finally, pay for a ride to LEO. That last one alone can be anywhere from $30k - $100k. There are, however, certain programs that give free rides to qualifying projects. We will look into that.

No money will be taken from anybody until we finalize design, however. So hold your horses. All in good time.

Edited December 19, 2014 by K^2

[Aethon]

Well you know we are unanimous in this. I'll help anyway I can.

To SPAAAAACCCEEEE!

[GluttonyReaper]

Voted for Phobos mission. I figure, if we can somehow get the additional funding and a free launch, we may as well try for something no-one else has achieved yet, rather than just another generic mission that doesn't really tell us anything we don't already know. Science for reals, guys!

EDIT from the far, far future: In hindsight, this wouldn't really be feasible at all, don't really know what I was thinking. Phobos still would have been cool, though.

Edited November 20, 2015 by GluttonyReaper
Change of opinion

[RRG]

Phobos is a good idea, but what could we do there with a cubesat beyond landing? And how exactly would we get there?

[K^2]

Phobos is a good idea, but what could we do there with a cubesat beyond landing? And how exactly would we get there?

Honestly, no idea what to do there after landing. Not like we could bring an actual drill along. Might be possible to blast the surface with some gas and do mass spec on it for composition. It'd be kind of expensive, but not unreasonably so. That's the only thing I can think of that can be done with landing, but not with orbiter.

Getting there is easier than one would think. Still not exactly easy, of course. The launcher would put cubesat on a GTO. Almost immediately, the main propulsion would kick in to change GTO to LTO. This would cost less than 700m/s of delta-V. That puts us on the course for Lunar fly-by. Except, at the top of LTO, the cubesat would be barely moving. Moon would sweep by and toss the cubesat out into interplanetary space going just a touch slower around the Sun than the Earth. Almost exactly a year later, Earth would catch up with the cubesat again. That's the Earth fly-by. If done correctly, that can toss the cubesat onto trajectory to intercept Mars. About half a year later, cubesat reaches Mars. Trajectory can be adjusted for Mars fly-by to have inclination that matches Phobos' orbit. A close fly-by allows aerobraking against Mars' atmosphere. That will take the cubesat from an escape trajectory to an orbit around Mars. A light boost at apoapsis would prevent further decay of the orbit. The most delicate part is the apoapsis itself, however. If it matches orbit of Phobos, the cubesat is already, effectively, on transfer orbit to Phobos. With a few adjustments and a bit of waiting, Phobos intercept is achieved. If all you want is Phobos fly-by or impact, you're basically there. If you want to orbit/land Phobos, you'll need to match its orbital velocity. From Mars transfer, that's 580m/s of delta-V. Total budget for lander/orbiter is under 1.5km/s from GTO to Phobos orbit. Total mission time, close to 2 years.

[RRG]

There is still the problem of the engine ISP and fuel fraction.

For dV=1500m/s and 1/2 Cubesat's mass of fuel: Isp=220, but to get this mass fraction we would probably need a 3U or 6U Cubesat, wich would need a lot of funds but it would be easier than reducing the fuel mass fraction.

For dV=1500m/s and 1/3 Cubesat's mass of fuel: Isp=370, wich migh be easy to do in a 3U but would need too high an Isp.

So to escape Earth's SOI we would either need a very good (and, I imagine, heavy) liquid fuel engine, or an Ion engine.

[Whirligig Girl]

Awesome. New thread.

[cantab]

If it can go interplanetary, I reckon Venus impactor is the most interesting idea. There hasn't been a probe enter Venus's atmosphere since 1985. With some suitable modern instruments we could learn new things about its atmosphere. It's also more forgiving in terms of precision than trying to aerocapture into orbit.

And yes, I think electric propulsion is required. This company (literally the first result I got for "cubesat propulsion" on Google) quotes 410 m/s in a 1U: http://www.busek.com/cubesatprop__main.htm

[Whirligig Girl]

I still vote for Geosyncronous Transfer Orbit (Using the launch stage, not the CubeSat itself), with an Estes booster to raise the Perigee or Apogee when needed. But One thing's for sure: A Kerbal Space Program Community Publicity Stunt needs to have an Estes motor. A C6-P motor would provide plenty of impulse, and it's be dirt-cheap. An Electrostatic Propulsion system for a 3U cubesat would increase the cost immensely, not the least because the CubeSat itself would cost much more.

If we can't go for GTO, a Moon flyby with an eventual gravity-assisted De-orbit would be cool. Especially with a camera to observe the Moon.

I really don't think we should aim too high for a publicity stunt. But if you insist on breaking the boundaries, Then Phobos would be the ideal mission, but we would need to accommodate the extremely expensive Electrostat.

Best case scenario we land on Phobos and we take pictures from the surface. Even better if we can manage to do some mass-spectrometer and take some sample of the surface.

If only Earth had a Minmus orbiting it. Then we could throw a Cubesat at Miinmuus.

If Asteroid Redirect Mission happens IRL before we complete even building the CubeSat, We could rendezvous with the Asteroid.

L1 or L2 wouldn't be at all fitting for a Kerbal Community mission, for Kerbin has no Lagrangian points.

And, as the Official Jebediah Kerman of the Community Space Program, I DEMAND Model Rocket Engines!

Edited July 15, 2014 by GregroxMun

[The Carrot King]

I think if you're serious about this and wouldn't mind the extra work, you could totally do this on kick starter. I've supported like minded project(https://www.kickstarter.com/projects/longmier/cat-launch-a-water-propelled-satellite-into-deep-s) and I'm sure with Squads support this could get big fast, plus it would be great for advertising.

[Tommygun]

Well if you eventually put it up on Kickstarter, the funding level achieved could determine the mission?

But there are still a lot of things to sort through first.

[Aethon]

Yeah, that was one of our ideas. Here's a link to some stuff we've talked about.

http://forum.kerbalspaceprogram.com/threads/85858-Pocket-SpaceCraft

[Aethon]

If it can go interplanetary, I reckon Venus impactor is the most interesting idea. There hasn't been a probe enter Venus's atmosphere since 1985. With some suitable modern instruments we could learn new things about its atmosphere. It's also more forgiving in terms of precision than trying to aerocapture into orbit.

And yes, I think electric propulsion is required. This company (literally the first result I got for "cubesat propulsion" on Google) quotes 410 m/s in a 1U: http://www.busek.com/cubesatprop__main.htm

Love it! Venus is fascinating.

Closer than we we're 5 days ago, but so far from a reality. This'll be a long haul!

[Rakaydos]

I think we should bill it as "The Kerbal Space Program Space Program."

And if we dont get enough to shoot for the moon on the first kickstarter, we send up a basic "Kerbal 1" mission, toot our horns, then immediately set up a SECOND kickstarter, for the Kerbal 2, with a higher minimum accept, but the knowlege, aerospace working relationships, and spare cash left over from the last kickstarter.

[K^2]

Yes. I was thinking that as well. It might be much easier to get the $200k+ for extended mission after doing a simple LEO one. But it's never too early to plan ahead.

There is still the problem of the engine ISP and fuel fraction.

For dV=1500m/s and 1/2 Cubesat's mass of fuel: Isp=220, but to get this mass fraction we would probably need a 3U or 6U Cubesat, wich would need a lot of funds but it would be easier than reducing the fuel mass fraction.

For dV=1500m/s and 1/3 Cubesat's mass of fuel: Isp=370, wich migh be easy to do in a 3U but would need too high an Isp.

So to escape Earth's SOI we would either need a very good (and, I imagine, heavy) liquid fuel engine, or an Ion engine.

Earth escape can be done in under 700m/s with Lunar fly-by. The 1.5km/s is what one would need for the Phobos orbiter/lander mission.

But you are right either way. With bipropellant options not practical for a cubesat, this will require an ion drive of some sort. Most likely, an electrostatic thruster, which can give you 600s+ I_SP. Unfortunately, most of these come with fuel pre-loaded and have pretty low total impulse. It might end up having to be a custom build. Hence such a huge gap in costs of the LEO and Lunar fly-by missions. But even 1.5km/s is achievable with an electrostat. So if we can get the budget, the option is on the table.

Still, we need more ideas for what to do in LEO if we can't do a Lunar fly-by.

Edit: The main problem with Venus impact mission is that a cubesat is not going to survive in that atmo very long at all. We'd be lucky to get one good data burst with mass spec from the outer most atmosphere. It's better than nothing, and would still make for the very interesting mission, but it wouldn't be my first choice. Of course, if Venus capture is the only good opportunity in the launch window we can get, then atmosphere analysis is probably the best mission we could do.

Edited July 15, 2014 by K^2

[Nicholander]

K^2, as I think it was suggested before, we could do a debris deorbit tech demo. Though the challenges are both 1), RCS and nav computers and navigation are probably not cheap and compact, and 2), I don't know the chances of us finding some debris smaller then a CubeSat, that's on an inclination that another NASA/ESA rocket is coincidentally going to. Also, 3), I think this is going to at least require a 2U size CubeSat, and maybe even a 3U.

[Aethon]

Yep.

The 'debris could be a detachable piece of the cubesat. Let it drift away, re rendezvous and either de orbit both, or whatever -it doesn't matter at this point, but this would be a valuable tech demo/ proof of concept.

Edit- Tho it seems to me this would require world wide tracking capability and some sort of autonomous, on board RADAR tracking capability, which sounds expensive... Unless we can come up with something 'outside the box'.

Edited July 15, 2014 by Aethon

[Nicholander]

I think another idea for an ultimate goal could be a Europa or Enceladus orbiter, though those fit into the Jupiter/Saturn Moons goal, I think those 2 moons are pretty different form the other moons, because the possibility of LIFE!!!. Though they are essentially impossible to achieve, I mean Europa/Enceladus orbital insertion is probably at least 1,000m/s delta-v!

[Robotengineer]

I know this is nigh on impossible, but a Titan or Europa impact, (or lander would be even better) would be much cooler and more likely to be funded then a LEO Sat. IMO.

[Nicholander]

Lander? I think it's barley Possible to land a U3 CubeSat on Phobos, let alone Europa or Enceladus. Though Titan does have an atmosphere, but what would we put on it that's not too heavy?

[cantab]

In terms of stuff within LEO, one thought is propulsion tests, developing the technologies that could propel cubesats to bigger and better things. I wonder, how hard can it be to make an electrical thruster?

Another idea might be a study on how the radiation environment affects off-the-shelf electronics. There've been a few cubesats controlled by smartphones, but I don't know if there's any formal investigation of how they perform.

Heck, I wonder if you could build a PC capable of running KSP and fitting in a cubesat

Yet another general idea would be some sort of long-term, sufficiently small zero gravity experiment. Might not be the most flashy, but I'm sure there are some useful things that haven't had the chance to go on the ISS.

Edit: And a final one, that perhaps has maximum cool factor: our very own space telescope! Small aperture means it will have modest capabilities, and attitude control will be a challenge, but I reckon some great images could come out of it.

[Rakaydos]

Lander? I think it's barley Possible to land a U3 CubeSat on Phobos, let alone Europa or Enceladus. Though Titan does have an atmosphere, but what would we put on it that's not too heavy?

a toothpick kerbal flag.

[Rakaydos]

Hmmm... for our electrostatic drive, what do we use for reaction mass? Hydrogen?

Random thought, but perhaps we could make a Venus Balloon.

[Nicholander]

Hmmm... good idea. Though the Soviets already did it with there Vega 1 and Vega 2 missions, I see no reason why not. But how big, heavy, and expensive would the balloon be?

[K^2]

cantab, good ideas. For propulsion, it'd probably have to be someone else's project. We can see if there are people who want to build/test something. A computer can be put into a cubesat, there are laptop mobos small enough, but we wouldn't be able to stream images back down.

Rakaydos, anything that enters dense enough atmosphere will burn up. We don't have mass reserves to do heat shield or burn away enough delta-V.

Anything with atmosphere is a valid target for an orbiter, however. Some, like Titan, are going to be extremely challenging, but simply due to the number of maneuvers it involves. In terms of delta-V, it's almost free.

But a landing can only be done on something with very small surface gravity. Which is a problem, because that means no atmo to aerobrake against. That severely limits potential targets. Phobos is nice, because it has very low gravity, but orbits a planet with atmosphere. But there could be some other targets within reach.