christok

Remember that we must have at least two complete and identical satellites as per testing requirements. I'd like to plan for three because otherwise we have no backup if something were to happen in construction. The test satellite(s) can be used as control(s) and then handed to some Kickstarter backer(s) with too much money on their hands. Those rad-hard parts could get expensive quickly. I'm willing to go with your choice of CPU. Anything we pick should be something with free tools so that we can share our work. I understand there already exist community-created cubesat boards with freely available Gerber files. It may be prudent to use or modify something that is flight-proven, even if it isn't our first choice of CPU. I found nothing in the cubesat specs prohibiting biological payloads. It will complicate thermal bakeout but I don't see that much of an issue. We will naturally start discussing this with Cal Poly and potential suppliers when we have a better idea of what we want. I'm against simulated regolith. An experiment can't study too many variables at once. In DIY satellite platforms: Building a space-ready general base picosatellite for any mission (2012. O'Reilly. ISBN 978-1-449-31060-8. p. 9), Sandy Antunes claims that for his project in the making (using a BasicX-24 computer), of less than 3 months projected flight time, radiation damage isn't a major concern. Although single event upsets are likely to scramble the sensors and crash the computer from time to time, I'm perfectly fine with not having 100% uptime in exchange for two orders of magnitude cost reduction if we can get away with it. Is your "weeks" expectation an educated guess, or do we perhaps have data for 8051 survival in LEO/something similar?

Patience. We're all still thinking over the numbers. Edit: K^2 is a ninja.

Light-hearted and yet so true: I'm still cool with a hinged solar panel deployment by centrifugal effects. Especially if the hinge is somthing simple along the lines of a length of fabric or flexible plastic rather than cold-weld prone metal hinge. (We'd need to choose a good material that won't become brittle and break after launch but that should be doable.)

I assumed we maintain spin based on the experiment we have been discussing. I had assumed the craft would spin up very slowly, although I may be guessing wrong about how much torque you want from those magnetos. I agree. We'll need hinges that won't cold-weld, for a start. Like Mazon Del, I still feel we should have some solar panels pointing out in the packed configuration. That would work if we had a second joint, but it does of course add complexity if we move them with servos. I am also not comfortable with servos repeatedly deploying and re-deploying in flight; that's bound to fail over a multi-month timeframe. (Possibly necessary depending on our thermal conditions.) I am also afraid of overheating in the sunflower configuration. If more of the craft is in the solar panels' shadows, that should improve our ability to heat-sink the experiment. I want to avoid garden-variety motors as much as possible. They're highly prone to failure in spaceflight conditions and there are all sorts of issues with things like lubrication, cold welding, etc. (Non-spaceflight) COTS motors are out of the question. Anything with a decent probability of working (especially repeatedly) is expensive to buy and we have too high a chance of mission failure if we try and design it ourselves. If it is problematic to deploy the panels with spin, I have two alternative ideas. 1: We release them with (very weak) springs before spinning up. 2: We add a few small coils of wire and deploy with electromagnetic repulsion. The nice thing about number two is that we can also retract the panels easily for night-time insulation, although we will need a mechanism to keep them in position without draining power. I'd definitely want to put the biosphere in a (flattened) cylinder. I'm thinking that this will encourage currents of air and water to compensate for our very small biosphere by distributing nutrients and heat as well as help compensate for asymmetries in mass distribution about the axis of rotation. Plants also grow towards the light. I think we should be more interested in how the organisms respond health-wise to partial gravity than the directions they grow in.

Microcosm has it for $100 (http://www.astrobooks.com). I can assure you they have everything we need (since I bought so much of it already ) but you can always check if Amazon et al. have a better deal. Speaking of which, we need to really start digging into the literature. I'm currently checking C.D. Brown's Elements of spacecraft design (2002. AIAA. ISBN 1-56347-524-3) to see what sorts of margins we will need in our initial design. - The closest to our category of spacecraft of a completely new design needs to count on a 50% mass increase from the initial bidding stage. (p. 26) - Our design should also not exceed 50% of the throughput capacity of the computer we choose. (p. 37) - Our thermal design needs the ability to handle 35C higher than the expected temperature maximum we calculate and 35C lower than the minimum we calculate (10C on either side for the "flight allowable" temperature, another 10C for our qualification and an additional 15C for the difference between what we design for and what we qualify the satellite at). We should calculate the thermal requirements on a per-component basis rather than a craft average. (p. 37) I am particularly worried about thermal design. As this satellite will carry living organisms with definite temperature requirements, without the battery capacity for any significant heating on the night side and with a very high surface:volume ratio, we will need to take care. - 40% margin on battery capacity. (p. 38) - 100% force/torque margin on the worst-case performance of mission-critical deployables. (p. 38) These numbers are of course not based on cubesats so we may have to fudge a little here and there but it's good to learn from what has already been done. Looks like we have our work cut out for us. Deployables are of course always a problem on spacecraft, especially cheap ones, but I was thinking something regarding our solar panels. We can significantly increase our power budget if the panels point towards the sun. Perhaps we can initially have panels on four sides of the cube, facing outwards so as to provide a smaller amount of power as long as any of them face the sun. When we are ready to spin up, we rotate the craft so that one of the other two sides faces the sun. On that side, the panels are hinged (without any motors) and the opposite side is attached with a once-off release mechanism. We then release the panels and spin the satellite up, allowing centrifugal effects to extend the panels. I'm sure someone in the industry has already thought of (and used) this, does anyone have any info? Edit: Mazon Del, I was paying so little attention I didn't even notice that's exactly what you proposed for the experiment. Not intended as an insult. I think it is better suited to the panels than the habitat but feel free to post counter-arguments.

This isn't lack of infrastructure, it is a deliberate choice. Cattle in general and cows in particular are holy in Hinduism, which is why India's first atomic bomb was also transported by cow.

When you lock microorganisms in a closed space, there is an initial extinction event as the local ecosystem goes towards a new equilibrium (the process is called "succession") but then the microbial density often goes up*. In general, the simpler organisms tend to survive more while the more complex organisms are likely to die off during succession. Over time the culture becomes senescent and mostly dies off, a process which unfortunately can take vastly different amounts of time for seemingly identical cultures**. However, the culture will survive essentially indefinitely if the entire range of metabolic features is present from the start***. A quick trip to your local pond can get you everything you need, although you want to be very careful in handling the resulting culture. A culture of potentially pathogenic organisms is far more dangerous than the few you had contact with when collecting the samples. This may make an ISS deployment problematic. Which is sad, because an ISS-launched cubesat can sometimes be recovered for ground-based study. In a monoculture, the process of growth and die-off is divided into five phases, known as the "lag phase" (initial adaptation in which bacterial numbers are stable), "exponential growth phase", "stationary phase", "death phase" (in which bacterial numbers decrease exponentially) and "survival phase" (the long tail of the death phase, theoretically never reaching zero and not mentioned separately by all sources)*. If we think our sat could survive for months, it might be good to go with some variation of a standard ecology experiment called the "Winogradsky column". (It is a diverse ecology in mud and nutrients, with aerobic and anaerobic microorganisms, some autotrophic and others heterotrophic, and possibly some plants.) The gravity gradient will be extreme with such a small centrifuge so I'm not sure how accurate it would be but any data is better than what we have now. In particular, I am concerned about the fact that plants would be at the top where the gravity is lower and that we might not get a long enough column for the anaerobic layer to survive. I'm not sure if any culture could survive very long without that anaerobic layer. * M.V. Kilgore, Jr., A.T. Mikell, Jr. & D.L. Pierson, Microbiological issues of space life support systems. (In S.E. Churchill, ed. Fundamentals of space life sciences. Vol 2. 1997. Krieger. ISBN 0-89464-051-8.) pp. 289, 297 **R.B. Thompson & B.F. Thompson, All lab, no lecture: An illustrated guide to home biology experiments 2012. O'Reilly. ISBN 978-1-449-39659-6. p 88. ***M. Nelson, Bioregenerative life support for space habitation and extended planetary missions. (In S.E. Churchill, ed., Fundamentals of space life sciences. Vol 2. 1997. Krieger. ISBN 0-89464-051-8.) p. 318.

My concern about using plants is that I'm not sure they'll survive the direct sunlight they need for photosynthesis. UV is pretty extreme up there and we may have to use an opaque container with artificial lighting. Or maybe not. But we'll have to research this so it doesn't lead to embarassing failures.

Man, that was a lot of reading for such a young thread. I love that so much. Pity it's just too ambitious for now. There just has to be a way to combine this with a biological experiment within the available mass/volume. There isn't much research on partial-gravity biology so it would be Real Science (33 points? I never really paid attention) if we pull it off. In case it isn't obvious, I'll contribute some cash at the very least. I'm worried about the containers being suggested for biological experiments. Being able to withstand the pressure difference isn't my concern, but rather at what rate they leak air and how that number will stand up to vacuum exposure, extreme UV radiation and large temperature fluctuations.

This is The Science Labs. Please don't bring your facts in here.

NASA donated ISEE-3/ICE to the Smithsonian many years ago. I don't see their permission anywhere so... Yarr!

Yes it would, and that is precisely the reason. Interstellar dust does little damage to a solar sail because the sail is thin enough for dust to pass through without imparting a significant amount of energy. (A spacecraft body, on the other hand, could need potentially mission-killing amounts of shielding.) The bigger concern is actually at perihelion since the environment very near the sun is not (last time I checked) understood well enough to know if the dust density is survivable.

The existence of the belt is deliberate. When a satellite nears the end of its useful life, it must be moved out of the most heavily populated orbits so as not to pose a threat to other satellites. Since equatorial GEO is the most coveted space but old satellites don't have enough dV to deorbit or escape completely, they are put in a nearby graveyard orbit (about 200km farther out, typically). The satellites in these graveyard orbits suffer natural perturbations, which cause their inclination to oscillate since active stationkeeping no longer takes place. Each individual satellite has its inclination vary between 0 and 15 degrees over a period of about 55 years*. Since the positions of the sun and moon are the same for all satellites, their orbits tend to form an approximate ring structure at similar inclination. * From J.R. Wertz, Orbits and astrodynamics. (In J.R. Wertz, D.F. Everett & J.J. Puschell, Space mission engineering: The new SMAD. 2011. Microcosm. ISBN 978-1-881883-15-9.) p. 219.

Antimatter isn't just normal matter with the electric charge reversed. It has the opposite charge in every respect. Except (probably but this is difficult to measure accurately) mass, which is it's own opposite. For example, an antineutron is perfectly well defined (and can be created) although it is electrically neutral. This is because its other quantum numbers (e.g. baryon number) are the opposite of the neutron's. Antimatter was proposed by Dirac and is best understood in terms of the motivation behind the proposal. The Dirac equation permits corresponding negative solutions for all positibve energy solutions (E^2 = p^2c^2 + m^2c^4), which would lead the state of any system go deeper and deeper into the negatives, since lower energy states are preferred. Dirac proposed that all of the negative energy states are already filled, by an infinite vacuum sea of particles (e.g. electrons) which exerts no net force on anything because it is uniform. The Pauli exclusion principle prevents "normal" electrons from lowering themselves to the negative-energy states of the vacuum electrons. Whenever one of the particles in the sea was knocked into a positive-energy state, the Pauli exclusion principle would no longer prevent a positive-energy electron from falling into the so created "hole", which would mutually annihilate with the electron when they encounter one another. (The electron lowers itself to the now-available negative energy state by radiating energy. The system is then in the vanilla vacuum state.) The modern interpretation of this theory is the Feynman-Stuckelberg formulation, which reinterprets the negative-energy holes as positive-energy "antiparticles". I used some details from D. Grifiths' Introduction to elementary particles, 2nd ed. 2008. Wiley. ISBN 978-3-527-40601-2. p. 21.

I said interstellar precursor mission. That's a mission to the interstellar medium, not a mission to other stars. Every year you add to the mission time increases complexity, cost and component failure probablities. Let's just say that spiraling out to Jupiter doesn't take a year or two on a solar sail. You make assumptions about the type of sail and method of deployment. That would negate all mass benefits of using the sail.

To be completely fair, I should actually have said additional solar panels. The payload will usually require less power while en route so you can use some of that power--but electric propulsion is still comparatively power-hungry. In any case, electric propulsion and solar sails aren't a case of either/or. One proposed way to do an interstellar precursor mission* is to use an ion drive to lower your perihelion, deploy a solar sail very near the sun, ditch the sail after a final solar-powered orbit adjustment about 5 AU out and then switch to the ion drive for any further adjustments. Or alternatively keep the sail, ditch the ion drive and point a big laser at the sail. The initial sunward dive would take too long to execute with the sail only (you don't actually want to lower your aphelion). * Refer to W. Seboldt & B. Dachwald, Solar sails--propellantless propulsion for near- and medium-term deep-space missions. 2008. (In C. Bruno, A.G. Accettura, Progress in astronautics and aeronautics, vol. 223: Advanced propulsion systems and technologies, today to 2020. 2008. American Institute of Aeronautics and Astronautics. ISBN 978-1-56347-929-8. pp. 443-445) for a discussion of how this could be used to study the Pioneer Anomaly. That particular problem has been solved but the proposal remains interesting.

That's not how you do the comparison. You should compare the total propulsion system to the total propulsion system. The mass of a solar sail plus all related structures (booms, tethers, whatever else you use) should be compared to the propellant, tank, engine and, importantly, solar panels needed to run an ion engine. They need a lot of juice and you need to include it in the mass budget.

The speed of light is not a measured quantity. It is the definition of the metre. 1 second = 9 192 631 770 oscillations of a caesium atom in an atomic clock, by definition. 299 792 458 metres = distance light travels in 1 second, by definition. 1 day = 86400 seconds, by definition (for scientific purposes). It isn't, of course, equal to a solar day (which varies in length) but it is a nearby and historically justified round number which may be used with SI values. I must be a real nerd. I didn't look any of those up. According to the Big Orange Book*, one light-year is "the distance travelled by light through a vacuum in one Julian year: 1 ly = 9.460730472 * 10^15 m". * B.W. Carroll & D.A. Ostlie. An introduction to modern astrophysics. 2nd ed. 2007. Pearson. ISBN 0-8053-0402-9. p. 58. (It's considered by many to be the standard textbook in astrophysics.)

Solar sails are hands-down faster than nuclear propulsion for long-distance missions. Low thrust doesn't matter much when the competition has to coast along 99.99% of the time anyway.

Starting point, in fact. Once you get to the bottom of the decision tree, it's an IFO.

It feels like something is missing. Perhaps a flashing banner with the promise of a prize once I enter my banking details?

The Planetary Society says its new "LightSail-1" prototype is ready for launch and promises a major announcement on the 9th of July (10th if you go by UTC). http://www.planetary.org/blogs/mat-kaplan/20140627-lightsail-ready-launch.html It ought to be interesting.

Much progress is being made behind the scenes. For example, one of the biggest problems with landing a probe on Venus is in cooling the electronics. NASA has many interesting papers on the topic of high-temperature semiconductors. I've linked to this search result https://solarsystem.nasa.gov/search/index.cfm?Criteria=high-temperature%20electronics in another thread; well worth looking at. In short, silicon carbide (and to a lesser extent gallium nitride) transistors are under development for use on Venus and (probably later) high-temperature environments in industry on Earth. These should operate nominally at temperatures exceeding Venus ambient and can already run for periods of over a year. The idea isn't to shrink the technology until we can run a hugely complicated computer on the surface. Instead, a surface probe could be given just enough computing power to be mostly remote-controlled, with the bulk of the computations performed by a satellite. Metallurgy has also advanced a lot from those days. When you read older books on high-temperature alloys (I have one lying on my desk at work; can't quote anything in this post) you'll see that much of the knowledge from the early days of solar system exploration was a mixture of partially-understood experimental data and hypothesis. Today's alloys are absolutely amazing in comparison. As a cool example, have a look at a jet turbine. Nowadays, the blades are made from special single-crystal nickel steels. (Normal steel is actually a mixture of ferrites/austenites/carbides/martensites and has a microscopic grain. This has no grain at all and is single-allotrope--I think austenite.) Such a steel can be (and routinely is) heated to more than 95% of its melting point* and spun at thousands of RPM, all without appreciable creep. For comparison, normal metals tend to creep an awful lot at around 50% of the melting point. Robotic surface exploration of Venus is within our grasp. But in my opinion we should hold on just a little longer before we can really do it properly. * I.e. about twice the absolute temperature on Venus.

The UN doesn't require it because the UN doesn't normally write laws. The requirement is part of the 1975 Convention on registration of objects launched into outer space.

According to the Outer Space Treaty: - Governements are responsible for the actions of their citizens in outer space. - Any objects launched into outer space remain the property of the launching nation. (Which propably has the property rights of the amateurs encoded in its local laws. If you launch illegally, your craft could probably be confiscated on the basis that it was used to commit a crime.) There are no salvage rights, even if it crashes in another country or gets blasted into space junk by an impact. - All spacefarers are envoys of humanity. They may not be detained but must instead be returned to their country. (This basically amounts to diplomatic immunity. Your own country could still arrest you for whatever you did, so don't get any funny ideas.) - The launching nation is liable for any damages caused by e.g. a spacecraft crash. (Your country would presumably slap you with a big fat fine and/or civil damages depending on local laws.) - You will certainly need permission from your local civil aviation authority as well as that of any nation whose airspace you intend to enter. Note that some greedy (non-spacefaring) countries near the equator try to claim that their airspace extends to GEO. You probably want to avoid those. - You probably need permission to handle explosives in large quantities for whatever propellant you use. - You will need a launch site. Probably be some military installation since you need completely clear airspace. This is often easier to arrange than it may sound, just by asking nicely and going through the channels. Also: The Secretary General of the UN must be informed of every launch, including planned trajectory. So at least you don't have to worry about being mistaken for an ICBM. Hopefully.