K^2

Interrogative mood is a tricky one, though. In English, it's pretty simple, indicated by certain grammatical structures and some key words. But in a lot of languages, it's completely down to intonation in a lot of cases. Try to ask someone a question in another language while knowing just a few phrases and not knowing the key words associated with asking questions in that language. You'll probably resort to making statements that explain your situation and hope the other person understands, rather than manage to ask a direct question. This might be the case with our attempts to communicate with other species. Or it might be that interrogative mood itself is a higher level linguistic constructs, so it's not natural in their native communication. I'd expect dolphins to have an equivalent concept. So I think it should be possible to organize a communication scheme where questions can be asked both ways.

Educated guess. And yes, random restarts are fine. Like I said, we can even add some extra checks to force a restart if something looks fishy. Maybe have canaries in RAM for the simplest check. ECCs for more important stuff. I did not realize that we need to submit a copy for testing. Does it have to have all functional components? That sounds excessively and unnecessarily expensive. We can build multiple sats, but it feels wrong to waste money on functional, space-hard photovoltaics and ICs. I plan to have off-the-shelf equivalents for every component. I can even come up with photovoltaics that are operational in rad-safe conditions. Will that do for testing? That's an order of magnitude in costs of the test sat, at least. Could you point me to the specific document that requests second sat for testing? Maybe I can find some loopholes. 8051s have been used. In fact, I think some of the commercial CubeSat CPU/RAM boards are rad-hard 8051-based. But I'd rather build a custom board for this. We can build several copies and even several iterations of the board and do all sorts of testing with it to make sure it's good. There are tools for doing some virtual testing of the board during design stages, there are good emulators for 8051, and we can outsource printing the actual board. Maybe even have basic components and sockets machine-soldered with something that will have good thermal ranges for the final series of builds. (I don't mind spending a few hours with a soldering iron with the first prototypes.) We'd talk to a number of potential launch opportunities before putting KickStarter up, and run the actual page by the top choice for sure. We have to know in advance all the options and what we can promise. And it'd still be nice to try and find a free ride from NASA or someone else.

Impossible to say. Expectation is on the order of weeks, but it could be much less or much more. Depends on solar activity, magnetosphere dynamics, and pure dumb luck. There are a ton of variations on 8051. I can see if some are going to be better than others at surviving radiation. But only rad-hard CPU will survive for a few months relatively reliably. (A good solar flare can knock out even one of these, so there is still an element of luck.) If no electronics fail, with ISS launch we might be able to count on about a year before orbit decays. So I agree that CPU should be a priority. And as I think I've mentioned earlier, that would be the #1 entry on the upgrade list. But if we have a ride and all other components, I don't think we should scrub the mission just because we can't make that final push. And a more manageable base goal on a KickStarter goes a long way towards getting funded, and having a chance to get extra funding before the launch. The other factor is that, like I said, 8051 is easy to obtain, cheap, and has a lot of tools and software developed for. A big part of why I want to go with that CPU is so that we can start prototyping the board and testing things without spending money on expensive equipment and risk ruining it.

It's not serious to try and ask people how much they can contribute until there is a concrete plan. Calm down. All in good time. General RFC. I'm putting together a shopping list. In principle, if we go with off-the-shelf CPU/MCU, we can go pretty fancy. But I think we are much better off by relying on architecture where any part can be swapped out to rad hard if funds become available. With that in mind, I propose using an 8051 CPU. It's easy to work with. There is a huge amount of tools available. It will make floating-point computations a bit tricky, but honestly, everything we need can be done in fixed point. It also has very low clock rate, so we wouldn't be streaming any video. (Not that I was counting on that.) It will be plenty for navs and attitude control work, and it will be able to handle communications with ground stations and transmit images. Best part, the off-the-shelf 8051 costs $10. So we can burn through a stack of them during development and testing without costing us. On the other hand, I've found rad-hard version of the same chip (UT69RH051) for $1,275. Expensive, but it's the sort of funds we might even find at the last possible moment, and still be able to swap out the off-the-shelf 8051 for a rad-hard one. I'm still looking at memory and other components. But it looks like I'll be able to make an absurdly affordable base package which we will be able to expand into something far more reliable with a very reasonable stretch goal.

Sat needs to expose eco-chamber to the Sun, which means that side panels will be poorly illuminated. We could get more power out of 4 0.5U panels that deploy to face the Sun, then from 4 full 1U panels fixed on the four sides. In fact, with deployment, it might be enough to just have two 0.5U panels. Seeing how solar panels are the most expensive part of the basic setup, I think it's worth extra complexity to try and keep the cost down.

Mazon Del, we are talking about total of less than 400ml of volume. What you suggest sounds a bit too complex for that. If there is budget for an inflatable, that would be something to try. But that presents all sorts of new issues and new ways for the whole thing to fail. christok, good arguments. If centrifugal deployment is really that much more reliable, I can work around it in the spin-up procedure. It will be a very gentle spin-up either way, since magnetotorquers will take time to get the thing up to speed.

There are a couple of minor problems with that. First, it requires spin to be maintained. That might be fine, as attitude control I have in mind sort of assumes it as well. The other part is that during deployment, that will change moment of inertia tensor rather suddenly. That can be trouble. These might be lesser problems than trying to articulate the panels, however. And by now, I'm also thinking that the craft should be a sunflower, with side panels deploying to face back, so that the craft can be oriented to expose both the eco-chamber and the solar panels to the Sun. Alternative deployment can be done with a pair of servos at the corners. Each one can extend two panels adjacent to that corner. The 10g micro-servos will be able to do the job just fine.

Should be possible with magnetotorquer. That's one of the cases where I could use axis tumbling to actually make the sat do what I want. But I'll need to do some sims to make sure. Basically, I want a principal axis running along the length of the sat, and magnitotorquer across. Torquing it towards parallel and anti-parallel with Earth's field will cause sat to spin along longitudinal axis. Axis tumbling will take any spin around mag field lines into longitudinal or radial spin, and I can adjust these with the torquer using a modified PID. Alignment with the sun can be done using a second magnetotorquer. Once the sat is spinning, it will work like a gyro. So a longitudinal torquer will cause rotation about the field lines, allowing the sat to orient itself towards the Sun. So the entirety of attitude control consists of a pair of coils with ferrite cores and amps to drive them. But again, I'll check that it all works in simulation first.

That's a lot of paperwork. Noted and bookmarked. Thanks.

The only advantage this could have over ISS and Earth experiments is low-G exposure. They've done microgravity on ISS, and hypergravity has been done on Earth. But it doesn't look like there have been any hypogravity experiments. No guarantee that it'd be useful, but at least, it fills in the gaps in the data. We could probably run it with Moon's gravity and maybe even get it up to Mars to see how viable hydroponics on Lunar/Martian bases could be. Radiation shouldn't be too bad in LEO, but at least one candidate species should be something that is particularly likely to do in strong UV. With NASA, the most likely ride would be via ISS, which would give us a very good starting orbit with as much as half a year before it decays. But it's likely to be extra strict on biologicals. A routine sat ride would probably not care what you put up there, so long as it's not harmful to humans if it's accidentally released. With ISS, things would definitely need to be checked with NASA on case-by-case. The container will be sealed. Exterior can be sterilized. But they might still want demonstration of ability to have nothing in the jar other than what's on manifest. That probably means we'll need help from a university bio lab equipped to handle something like that. But that, in itself, isn't tricky to get assistance with. I'm sure there are plenty of unis that wouldn't mind giving students some exercise in whatever's the bio equivalent of clean room procedures. What I mostly need to know from someone who's bio savvy, is what's the minimal diversity needed for a closed system to survive for up to half a year? What I need in there to get the ball rolling? And what temperature ranges should be maintained? Ideally the temperature range should be as high as possible. That will probably affect the choice of the species. One more thing. Before we can get sat in orbit and establish the hypogravity environment, the container will undergo significant over-G followed by considerable length of free fall. I'm sure whatever's inside can weather it out, but mostly that's to point out that what we have inside can't rely on gravity or its lack for staying put. If jar isn't completely filled with water, that water will slosh about. So will any loose soil. I suppose, a solution is to simply deal with the volume being completely filled with water, but that will both increase the mass of the sat, and will reduce impact of hypogravity. It'd be more interesting to see how plants can grow above "surface", I would imagine. But it might be possible to have something like a clear sponge to act as "soil" and have some algae or other organisms in that sponge. Anyways, just some thoughts and technical limitations. P.S. Bonus points if the plant or full ecosystem could actually be useful to a Lunar/Martian base. Naturally, growing crops is out simply because of available volume.

Charging despicable batteries. It might be a good idea to have them angle a little. But not, strictly speaking, a requirement. I think it's about time to put together a "shopping list" and see. I'm still hoping to be under $10k for the base unit. But that doesn't include launch or ground support. I'll find out what requirements are from NASA for an ISS launch or similar, and see if there is any way this mission can qualify for a free ride. So I'll get back to you with some numbers shortly.

Well, batteries need to last for half an hour at the most. And in fact, it's not a tragedy if the thing resets due to bad batteries. Just means we wouldn't be able to test things on the dark side. So I wouldn't stress over it too much. If we have the budget for better batteries, something designed for space, we'll go for it. But controller and memory would come before that on my "must upgrade" list. Again, pending availability of the funds. Base budget can be designed around an off-the-shelf MPU. Like I said, I'll look into some software error-correction options. Error-correcting memory is awesome, but it's pricey, and rarely includes anything more fancy than a parity bit. I can build an architecture with a co-processor whose sole job is managing memory in Zp using polynomial error correction. But that will slow things way down if each read/write will have to go through a separate processor. Anyways, can't go cheap on solar panels. Then first to upgrade are MPU/memory, then battery and sensors. Finally, cameras. I suspect rad-hard cameras to be very expensive. And then we can look into expanding experiment. Tethers, 2U, that sort of thing.

Centrifuge won't cost anything, because the entire sat will spin. I'll just need to figure out how to make that happen with magnetotorquers without causing it to tumble. Most likely will be down to balancing all of the components very carefully. And I honestly can't say yay or nay for any suggestions on flora or fauna. You can suggest cats, and I'll be all, "Yeah, that's awesome. They'll have to be tiny cats, though." If you ever need an example that proves that publication on cellular biophysics does not make one an expert on biology, feel free to point in my direction. I will definitely at least talk to someone from bio about this, though. Sensors, lights, and anything else hardware related can go on the hardware side of the cube. There'll be some room there. Plus, it's easier to just stick everything onto a single printed circuit board. But yeah, it's part of the reason why I'm not sure about oxygen sensor. These things tend to be bulky. In cars, at any rate. I'll look into that. So the .5U should be just the jar with the plants. I'd like to have glass jar, but that might be problematic. In which case, perhaps, acrylic? Or plexiglass? That will be like a an open gate for radiation and UV, however. Might be a bit much. On the other hand, figuring out what will and will not survive space rad is part of the experiment, I believe.

Hm. I think, amount of chlorophyll can be estimated by exposing plants to UV (while on the dark side, using UV LEDs) and measuring red/IR light intensity. An oxygen sensor is also not completely out of the question. And there is visual, of course, from the rear-facing camera. I'll poke at some biologists as well, but it'd be nice to have someone from community.

With ionizing radiation, the only thing that matters is center of mass energy. Not the type of particle that delivers it. Granted, at moderate energies, a proton will deliver higher CoM energy in collision with an electron simply due to its mass. So that could be a factor. The other thing is that there might be more charged particles than energetic photons coming in from the Sun. But otherwise, the two types of radiation are the same. Looking at some info on Wikipedia, it looks like most dangerous radiation is going to come from Solar Particle Events, which results in up to 10MeV proton bursts. That's heavy ionizing radiation, but the protons themselves are going to be strictly classical due to their mass, traveling at roughly 1% c. If you try to deflect these with a mag field, cyclotron radius formula applies. p = Bqr. At 1 kGauss, that's over 30cm turning radius. I'm having hard time picturing a stronger field around a cubesat. So no, I don't think magnetic shielding is viable. Tethered centrifuge is significantly more complicated to pull off in terms of attitude control. I also can't picture it anything other than a 2U mission. That could be a budget+ option. But for base, I'd go with a jar fixed within the body of a 1U, with about half of the volume taken by a 10x10x5 pill box jar, and the other half with electronics and attitude control hardware. Sensors can go into corners around the jar as well. Solar panels can then probably go on the sides. Back wall would be open, allowing sun light. Two cameras can be installed on the board, one pointing forward, the other back through the jar. If we want to generate up to about 1m/s² of artificial gravity in the jar, we can just spin the whole sat at roughly 30RPM. Spinning much faster than that would make it difficult to track rotation with horizon sensors. And I doubt we can completely avoid axis tumbling or some excess torques. Hopefully, however, the whole thing can be corrected with magnetotorquer. How does that sound for basic mission? Because this we can probably put together on minimum budget. I know bugger all about biology, however. I know people have made some completely enclosed mini-biospheres with some algae and plancton. But I've got no clue what one would need to set this up. I can add anything we need to control temperature and lighting to the shopping list. As well as a Geiger counter. But I'd need someone to tell me exactly what the parameters should be. Anyone here has a green thumb and/or some biology know-how?

Not really. At relevant energies, it's just about having electrons to scatter from. Be it charged particles, beta or proton radiation, or gamma radiation. Now, in terms of neutron radiation shielding, yes, things are different. But neutron radiation isn't as significant. Until you get into heavier elements, electron density is basically proportional to mass density. So you get same protection from equal weights of water and air. About 1atm worth. Lead ends up being a bit worse, because it has more neutrons in the nuclei. But it's pretty close. It does, however, provide better neutron shielding. High density makes it more compact as well, which is why it's a common material for shielding. Just as above. Because density is lower, you need a bit thicker layer. But weight of lead shielding or titanium shielding will be about the same. And you can dual-purpose your heat shield as radiation shield, yes. There are some interesting differences at lower energies, but these tend to be absorbed even by the thin skin of the sat and don't cause as many problems. It's the rare, but very energetic particles that usually screw things up. A few people suggested an inflatable biosphere. I'm worried that it might be a bit too prone to failures. However, a jar should be easy enough. Even with magnetotorquer and a gyro for attitude control, most of the space in the 1U frame can be left empty. That can easily have a jar with some plants in there. Maybe even some plankton or similar in a liquid solution. I really like the idea of setting up artificial gravity in there. I'm pretty sure it'd have to be much less than 1G, but that only makes it more interesting. I don't think anyone has done any studies on plants in low gravity. Unless there has been some centrifuge experiments on ISS that I'm not familiar with. (I'm half-expecting someone to jump in with, "But there have been!" link right about now.) Anyways, that's pretty doable, and there could be some interesting things to do with it. Inflatable might still be viable with better funding, but how about "life in a jar" for basic? It's something that can be done on the target "under $10k" budget, and it might have some value as an actual research project.

AngelLestat, this project needs low level localization and navs code. Compared to that, writing a few drivers for the sensors and servos is child's play. We will find a team of capable people. Don't worry about that. But even if I would have to write software myself from scratch in my free time, it's a matter of a few months to get the framework ready. It will take longer to get all of the necessary clearances, find quality hardware, and begin construction. As for batteries, they don't need radiation protection as much as processor and memory do. Battery will degrade from radiation, but it will do so gradually. It's not something that will just randomly quit on you after a random time interval. Battery's temperature needs to be regulated, however. That might be where the talk of insulation comes from. That has nothing to do with radiation. Just the fact that you are working in a vacuum with a short day/night cycle.

It takes ten meters of water to provide same kind of radiation protection that our atmosphere gives us. You don't need that much, but reasonably, you need a few inches of lead to make a significant difference. Good luck. Having written code for MCUs, having participated in robotics competitions, having written computational code for superclusters, and having a software engineer job lined up, I'll take my chances with the software.

Just matter of luck and Solar activity. It takes one gamma through the wrong part of the chip, and it's out. Tends to be matter of weeks, if not days. But it could all end a lot sooner, so it'd be a risk. And yeah, I think I've heard of a cubesat with a Raspberry Pi before. At least, in planning.

Fortunately, it's relatively easy to obtain an unlocked GPS unit. So like I said, the only real advantage of a phonesat is easy access to camera, and Sky have demonstrated why even that can misfire against us. Might as well just build all the electronics/software from scratch. Neither needs to be all that complicated. In fact, the simpler, the less the chance that something goes wrong, under the circumstance.

Logic and manufacturing techniques are different. Rad-hard CPUs are typically built on different substrate with more redundant elements and some ways of catching errors. Shielding just isn't going to cut it. Sufficient shielding would simply weigh too much for a cubesat.

Part of why I don't like idea of a phonesat. Even if it can be rigged to auto-reboot on crashes, it's going to take time. For an MCU, custom code can be written to do some error-checking/correction on the fly and reboot automatically and quickly on any critical crash. But it's still going to be just luck whether the thing last an hour or a month from there on. I would very much like to have an option to spend a few $k on a good rad-hard CPU, though. Compared to other costs, it's fairly reasonable.

I'm basically going to see if I can build an S-band ground station and have it communicate with something already in orbit. (A number of cubesat projects have open comms protocols.) Almost all of the components are going to be salvage, so it's dirt cheap, but it might take a bit of time putting everything together and writing control software. S-band is a good choice if we end up going with a phonesat, but there are a number of high quality s-band transceiver options as well. So it's a pretty safe choice. We really should try and see if there is a good 1U free LEO ride option we can get in on, because that's going to be the most expensive part of the basic mission. Everything else can be done on a modest budget.

Simplest way would be to have a USB MCU on board that talks to the phone. Though, to be honestly, the only advantage of the phonesat is working with a camera. For everything else, it'd be better to just have a better MCU that controls everything. Phone GPS would probably be useless in orbit, since they are usually locked to within certain velocity ranges. And accelerometers are cheap either way.

Most of the components are absurdly overpriced. Only a few should be purchased from specialized cubesat vendors. It should be possible to fit within $10k for a unit with solar power, comms, and attitude control. Propulsion would be extra. Of course, if propulsion is basically the experiment we want to do, then there's that.