NERVAfan

Probably somewhere in the ballpark of two or three weeks, limited both by orbital decay and moss survival...

Ah! Well, that's because we're taking about two totally different things. Spirulina is a cyanobacterium ("blue-green alga") not a moss. The lower numbers (15-25 C) I just posted apply to the moss Physcomitrella patens. CubeSat LEO orbits tend to decay fast enough not to present a debris hazard. The recent KickSat cubesat (deployed from the ISS) burned up in a few weeks. Endersmens started to set up a website: https://sites.google.com/site/kspcommunitycubesat/home

I think solar electric propulsion for higher thrusts might be more feasible if you had large areas of very light thin film panels mounted on a very light structure. JAXA proposed a mission like this as a follow-on to the IKAROS solar sail, but I haven't heard anything new since so don't know if it is still planned.

Where does the 36 C number come from? A range of 31 C - 41 C sounds rather too hot from the (admittedly limited) information I have been able to find. "Even tropical bryophytes seem to do poorly above 25°C (Frahm 1990), where their net assimilation rate decreases drastically, respiration rates are high, and they fail to reach their compensation point" "Indeed, for most bryophytes, the optimum is near 20° C and for many it is much lower." "Physcomitrella patens developed capsules best at 15-19ºC, " Hohe et al. (2002) found that the highest number of sporophytes in Physcomitrella patens were produced at 15ºC, with numbers dropping greatly at 25ºC. Vegetative growth, on the other hand, was best at 25ºC. " Glime, Janice M., 2007 Bryophyte Ecology http://www.bryoecol.mtu.edu/ . "the lethal cold temperature for 50% mortality (LT50) for P. patens protonemal tissue is around -2 C" Annual Plant Reviews, The Moss Physcomitrella patens [Protonema = the shoot that sprouts from a moss spore] So maybe we should be shooting for more like a 15-25 C range. But we should talk to someone who actually has experience growing this species. Growing conditions information doesn't seem to be easily available online.

OK, so is this the general concept? (Excuse the MS Paint...) I guess there should be some oxygen/CO2/humidity sensors in there somewhere too? EDIT: this is meant to be just the plant part of the cubesat, not including reaction wheels, communication equipment, solar panel etc. - I know we need those things too. But it would be nice to have the plant-part designed early so some of us can try out a similar design for growing stuff on Earth.

Unfortunately, creating sugar through photosynthesis consumes water.... 6 H2O + 6 CO2 -> C6H12O6 + 6 O2

Daedalus is nuclear pulse propulsion too, just a version not involving actual nuclear bombs. (although to be fair, a real Orion would use nuclear devices optimized for propulsion. It's not REALLY a matter of grabbing nuclear warheads off a military base and pitching them out the back of a spaceship). I do think nuclear pulse is the best interstellar technology, as it allows really big ships and thus heavy shielding - I'm skeptical of the light laser/microwave/whatever beamed sail craft that are proposed surviving interstellar dust collisions. EDIT: best that doesn't require any major breakthroughs, that is. Antimatter rockets or Bussard ramjets or FTL drives or whatever would be better.

Yeah, I don't understand why this isn't in the stock game.

Jet engine thrust is way too high... I was playing around with putting them on wingless rockets and they are IMO way too good for vertical takeoff. They should not be competitive with standard rocket engines for wingless, vertical takeoffs.

I think the real problem for life in Venus' clouds is lack of water (water vapor content of Venus' atmosphere is only like 20 ppm). There are super-acid-resistant microbes on Earth, such as those involved in acid mine drainage.

OK, so what has been obtained and what still needs to be obtained? And who will be launching it, and from where? If the launch is US, I believe there is a weight limit below which you don't need FAA permission.

Yeah, cubesats in LEO deorbit pretty fast. Not just the lack of propulsion, but also (if I understand it correctly) there's a square-cube law thing where drag has more effect on smaller objects. The KickSat cubesat deorbited in just a couple of weeks.

OK so if we're going with moss instead of Spirulina.... ...where would we get samples of this moss? It would make sense to grow it on Earth first in a similar environment... what will the moss-containing part of the cubesat be like? How much space is left over after the electronics and insulation etc.?

New Horizons launched directly into a solar escape trajectory on rocket power alone; it did do a Jupiter gravity assist to speed up later, though. The third stage is also on a solar escape trajectory... So I'm pretty sure existing rockets could do it for an unmanned probe, theoretically. But... Yeah, exactly. Maybe we'll have fusion engines by the 2080s; that could reduce the trip to a reasonable length. Also, medical technology may have advanced by then to the point that cancer isn't really an issue. (You'd still need some kind of shielding for solar flares though.)

I don't think it's a "fly a payload" opportunity; it appears to be a contest for people to submit ideas for what kinds of payloads NASA could use to replace the balance masses.

Arabidopsis thaliana is not a moss, it's a flowering plant in the mustard/cabbage family (Brassicaceae). It is also probably too large for a 1U cubesat (Wikipedia says "usually growing to 20-25 cm tall") if it has any time to grow. Cool, if it can survive long enough in the dark. OK, that sounds promising. Hmm, OK, the moss is sounding a lot more viable than I had expected.

Yeah. Spirulina is potentially useful for life support systems and apparently has fairly broad environmental tolerances. It's actually a cyanobacterium (aka 'blue-green alga') rather than a true (eukaryotic) alga, by the way.

Yeah, that sounds super interesting! What is its status?

I would certainly be willing to buy and grow it, but what exactly will we be testing? Just growing it won't help much -- we would want to e.g. replicate the container/habitat that will be used on the spacecraft, or the lighting/temperature conditions, etc. But those parameters haven't been decided on yet. It's definitely a step we should take (given the price!) but not quite yet... let's get a bit more of a design first. --- Also, potential Cubesat launch opportunity to Earth Escape in 3rd Quarter 2016 (price is $750k for a 3U, though!): http://www.parabolicarc.com/2014/09/11/spaceflight-offers-deep-space-rideshare-opportunity/

You can buy live spirulina cultures from Amazon: http://www.amazon.com/Algae-Research-Supply-Spirulina-LiveCulture-010/dp/B00C4VMF4W/ref=pd_sim_indust_5?ie=UTF8&refRID=1RAN748MFDG42D3HM7HR http://www.amazon.com/Algae-Research-Supply-Algaekit-002-Kit-Spirulina/dp/B00E9OFSKA

On spirulina temperatures - from an FAO document on spirulina farming (http://www.fao.org/3/a-i0424e/) "Spirulina shows an optimum growth between 35 and 37 °C under laboratory conditions. Outdoors, it seems that an increase in temperature up to 39 °C for a few hours does not harm the blue-green alga, or its photosynthetic ability. Thermophilic or thermotolerant strains of spirulina can be cultivated at temperatures between 35 and 40 °C. Such a property has the advantage of eliminating microbial mesophilic contaminants. The minimum temperature at which growth of spirulina takes place is around 15 °C during the day. At night, spirulina can tolerate relatively low temperatures. The resistance of spirulina to ultraviolet rays seems to be rather high (Richmond, 1986). " Also possibly interesting... "Alkaline, saline water (>30 g/l) with high pH (8.5 – 11.0) favour good production of spirulina, especially where there is a high level of solar radiation at altitude in the tropics" "The higher the pH and the conductivity of the water, the greater is the likely predominance of Spirulina spp. This is the case in the lakes of the lakes of the Rift Valley of eastern Africa, where pH can reach values close to 11 and sodium carbonate is abundant. Spirulina platensis was isolated from waters containing from 85 to 270 g of salt per litre, and optimum growth occurred between 20 and 70 g of salt per litre. " Well the Atomic Rockets site says eating a diet based on it could cause gout. I don't know if that has ever happened though.

Spirulina is interesting. The Atomic Rockets website has a big discussion on its use in life support systems; apparently it's pretty awesome, but a Spirulina-based diet might lead to gout. (I'm not sure if anyone has ever actually done that though. The Wikipedia article links to experiments where they fed rats tons of Spirulina, but rats and most non-human animals IIUC aren't really susceptible to gout*) *Although T. rex apparently was.

It's not a matter of "trust", IMO, since fun is different for different people. I think it would be awesome, but maybe most people wouldn't. The point isn't to bring it back to Kerbin/Earth to sell, but to use it in space. (And Planetary Resources seems to think they can mine platinum group metals from asteroids profitably.)

Makes sense. So can we get good gravity results with plants/algae suspended in water?

Yeah, the growth thing is one of the tricky bits. There are quite a few options that would be great (endures sunlight, dryness etc.; fits in a tiny space) except for being slow growing (lichens, living stones...) Well, SpaceX plans Mars first too... That's a good question. What do other cubesats use? What's the temperature tolerance of the electronics in, say, a PhoneSat smartphone?