KSP Community CubeSat

[B787_300]

nice little report on nano and micro sats and launches

http://spaceref.biz/company/spaceworks/spaceworks-releases-global-launch-vehicle-market-assessment-report-for-nano-and-microsatellites.html

[KSat]

Hello fellow Kerbonauts,

yes we might be able to help you. Time is limited to everyone of us, so we might not be able to put that much effort into your project, but I like to overlook your mission plan for feasibility. I also have access to a number of space flight experts that are able to answer trickier questions.

Can somebody be so kind and give me a summary of what you are exactly planning to do?

As the 66 pages are a lot of segmented reading...

Another project done by my team and other european students was the european student moon orbiter. The project survived a PDR before it was cancelled by ESA.

Cheers,

KSat

[Mazon Del]

In general what we appear to be shooting for is a cubesat (seems like people say 1U, but if additional funding, up to 3U) that would have a chamber for the purposes of growing plants. This cubesat would be spun to produce 'gravity'. We are currently leaning towards a 0-1g range as experiments on Earth have already done >1g growth. Desired sensors currently involve 2 cameras (internal, external), temperature, humidity, light, oxygen content.

[AngelLestat]

Hello fellow Kerbonauts,

yes we might be able to help you. Time is limited to everyone of us, so we might not be able to put that much effort into your project, but I like to overlook your mission plan for feasibility. I also have access to a number of space flight experts that are able to answer trickier questions.

Can somebody be so kind and give me a summary of what you are exactly planning to do?

As the 66 pages are a lot of segmented reading...

Hi Ksat, any advice that you can give us would be very welcome. Thanks for your time.

I guess K2 is the right guy to give you a summary of the main ideas.

The idea most studied so far would be plants growth in microgravity environment. Following the Mary Musgrave´s reasearch.

http://today.uconn.edu/blog/2009/08/the-effects-of-gravity-on-plant-growth-and-development/

K2 or other forum fellow can give you more details over this.

My concern and personal question would be this:

What you would recomend as our first mission?

For example I was look at the possibility to use a smartphone to cut expenses. It would be advisable with a mission lifespan not longer than a month?

What are your thoughts about Electrodynamic Tethers?

If we rely on this paper: http://enu.kz/repository/2010/AIAA-2010-8844.pdf

Maybe we can test a 2U 1600m tether (total 1,1kg for all tether components and systems) or 1U (with shorted tether) to test this technology as propulsion system, gravity gradient and energy harvesting.

Edited July 23, 2014 by AngelLestat

[Rakaydos]

There is also a minority of us looking into a technology demonstrator for a cubesat based mission beyond earth's sphere of influence.

Using a Geosynch Transfer Orbit ride and burning under our own power to a Lunar Transfer Orbit to slingshot out of the earth/moon system. Idealy, we would like to target a solar orbit with a 1 AU semimajor axis, which would be nessisary for a timely earth-slingshot, which would be considered a total succeed in our primary mission. This slingshot capability would demonstrate the capability to (hopefully affordably) send cubesat-based hardware to Venesian or Martian sphere's of influence, without requiring independant launch hardware. (it being a cubesat piggyback on a commercial geosynchonus orbit launch)

Currently, we (the minority interested in this advanced project) are looking at a 3U with at least 600 m/s of delta V and sufficient guidance capability to make the required burn, and a basic heatshield to practice aerocapture with (either after a 1-year orbit, or at a more distant destination). Any mass we can reserve for advanced projects, we may be able to sublet to other interested parties.

(The "Phobos mission" group is an interested party here on the forums, but the D/v + TWR requirements are a bit steep for what we can fit in a 3U, and requires everything else to go perfectly first- so certainly not something to go on the first mission.)

[RocketmanRower]

Hey guys. IRL I go to MIT and my professor and lab research head is working with the Time Capsule to Mars project (http://www.timecapsuletomars.com/). The electrospray ion thruster are relatively simple and I can find out more info about the cost. They only require 150 grams of fuel to have the delta-v for a transfer from LEO to Mars. I also know people in astrodynamics who could help with aerobraking and transfers at Mars; some of my friends and I could work on it for our dynamics modelling class next semester for our final project I bet. At least we'd get the skills necessary to make a rough outline. A lot of tech development is currently happening for this sort of thing, it just comes down to money (like every problem in space flight). Someone should start to organize a type of kick-starter/a fundraising campaign.

[Nicholander]

KSat, too bad the ESMO was canceled. Also, great RocketmanRower! those MIT guys will be great help for our project. Also, I think someone should make thing in Orbiter of our CubeSat (Both the Phobos and LEO), I would but I have NO IDEA how to mod Orbiter.

[KSat]

Hello fellow Kerbonauts,

I will post here some comments about the plannend stuff. But although I have some knowledge in spaceflight and spaceengineering, I might get some things room or have overseen some details.

In general what we appear to be shooting for is a cubesat (seems like people say 1U, but if additional funding, up to 3U) that would have a chamber for the purposes of growing plants. This cubesat would be spun to produce 'gravity'. We are currently leaning towards a 0-1g range as experiments on Earth have already done >1g growth. Desired sensors currently involve 2 cameras (internal, external), temperature, humidity, light, oxygen content.

Spinning to produce gravity:

You will need to spin to create 1g on the outer edge of the spacegraft

for 1U: 14 rad/s or 2.23 1/s

for 3U: 8 rad/s or 1.285 1/s

How are you going to generate the momentum for the spin?

Reactionwheels certainly can help but are comparable heavy and use a lot of volume.

Magnetorquers are pretty weak but might be able to do it, you need attitude sensors and controllers to power the magnetorquers at the right time to spin up.

Cold gas thrusters. Easy to do, but as far as I know only low pressurized gas tanks with inert non toxic gas is allowed, which limits the ÃŽâ€v.

Sensors:

Cameras - cool , small and cheap , if you have the bandwidth to transmit the pictures/videos best you can do.

Temperature - mandatory. It does not matter what experiment you are planning you need Temperatures sensors. You have electric components producing heat and the sun from one side providing substantial heat flow. When you are near earth the temperature of the earth adds up to the heat flow as the reflection from sunlight of the earth onto the spacecraft. So at every moment you need to make sure that your spacecraftcomponents are within the acceptable temperature range.

Humidity - should be easy , as every cheap thermometer contains one.

Light - is already done with camera

Oxygen - should be of the shelf

I have some questions/concerns how to realize the experiment.

How do you think to sustain the pressure of your experiment?

You will probably have a lot of probes and stuff going in and out, making it leaky.

So some atmosphere will get lost, replacing it is tricky as only low pressure tanks with inert gas (not oxygen, better CO2) is allowed.

"No pressure vessels over 1.2 standard atmosphere shall be permitted. "

How do you make sure your experiment set up survives till orbit?

I envision a containment with soil as the ground and seed in the soil that are able to break trough the foil(?) into the pressurized part of the containment.

If so how to make sure that the g-load during launch will not rupture said foil, or spread the soil all over?

You probably already have seen this document, but to be sure:

Cubesat Requirements

http://cubesat.calpoly.edu/images/developers/cds_rev13_final.pdf

Cheers,

KSat

Edited July 24, 2014 by KSat
forgot cubesat requirement link

[KSat]

Hello fellow Kerbonauts,

I will post here some comments about the plannend stuff. But although I have some knowledge in spaceflight and spaceengineering, I might get some things room or have overseen some details.

For example I was look at the possibility to use a smartphone to cut expenses. It would be advisable with a mission lifespan not longer than a month?

Smartphones are a cheap alternative to space qualified bord computers and have already flown.

https://en.wikipedia.org/wiki/STRaND-1

https://en.wikipedia.org/wiki/PhoneSat

For a missision of less then a month radiation should not be that harsh, but some shielding should be implemted. In general sensitive parts are placed in a spacecraft, where it is shielded by other less sensitive parts. Also from your orbit you can expect an increased radition flow from prograde direction (electrons).

What are your thoughts about Electrodynamic Tethers?

Tethers are great, but not that much tested yet.

What you can do with a tether?

Propulsion: You transfer some electric energy of your spacecraft into the orbit energy of your spacecraft. You therefore need some equipment that already has that electric energy.

Gravity Gradient: Totally passive and no problem, especially not for a cubesat. The tether makes sure that the craft always points "down" to earth gravity center.

Energy harvesting: Reverse process of propulsion. You trade your orbit energy for electrical energy. For example you can start a deorbit with a tether when you are able to dissipate the electrical energy into heat.

It depends on your mission. If your starting orbit is high enough, you might be able to feed on your orbit energy until you start reentry. Therefore no other power generator would be necessary. If you plan a longer stay solar cells are needed and you would be able to maneuver in earth orbit.

But one major concern. The elecitrical power by a tether is big and a cubesat is small, if you go for the tether you need to make sure you can survive the power output of the thether.

Resistors would produce a lot of heat so probably a shorter tether is the easiest solution when power is to high.

Cheers,

KSat

[KSat]

Hello fellow Kerbonauts,

I will post here some comments about the plannend stuff. But although I have some knowledge in spaceflight and spaceengineering, I might get some things room or have overseen some details.

There is also a minority of us looking into a technology demonstrator for a cubesat based mission beyond earth's sphere of influence.

Using a Geosynch Transfer Orbit ride and burning under our own power to a Lunar Transfer Orbit to slingshot out of the earth/moon system. Idealy, we would like to target a solar orbit with a 1 AU semimajor axis, which would be nessisary for a timely earth-slingshot, which would be considered a total succeed in our primary mission. This slingshot capability would demonstrate the capability to (hopefully affordably) send cubesat-based hardware to Venesian or Martian sphere's of influence, without requiring independant launch hardware. (it being a cubesat piggyback on a commercial geosynchonus orbit launch)

Currently, we (the minority interested in this advanced project) are looking at a 3U with at least 600 m/s of delta V and sufficient guidance capability to make the required burn, and a basic heatshield to practice aerocapture with (either after a 1-year orbit, or at a more distant destination). Any mass we can reserve for advanced projects, we may be able to sublet to other interested parties.

(The "Phobos mission" group is an interested party here on the forums, but the D/v + TWR requirements are a bit steep for what we can fit in a 3U, and requires everything else to go perfectly first- so certainly not something to go on the first mission.)

This plan is at least hardcore. You probably have in some simulation tool made already an example of a trajectory that could fit that.

But the Computer simulations are always a simplistic version of reality. The gravity fields of moon and earth are not spheres and not even ellipsoids.

On your interplanetary journey you have disturbances by solar wind and radiation pressure. You have burn errors, that are small (impossible to avoid) while burning, but they matter big in the end. Also the atmospheres are highly dynamic and the aerobreaking maneuver therefore highly uncertain. For example the upper atmospheric density depends on the solar activity, which will change during your mission time.

All in all, this is very tricky and you would need alot of equipment that is able to detect and correct trajectory errors and safety margins for fuel.

Also for interplanetary communication you would need acess to the Deep Space Network.

Heatshields are a topic for themselves, ceramics are expensive and ablators are tricky to calculate.

Conclusion: Slingshots maybe. Aerocapture hard.

Cheers,

KSat

[K^2]

Spinning to produce gravity:

You will need to spin to create 1g on the outer edge of the spacegraft

for 1U: 14 rad/s or 2.23 1/s

for 3U: 8 rad/s or 1.285 1/s

How are you going to generate the momentum for the spin?

I don't actually think 1G is a reasonable goal. I've mentioned before that 1m/s² is quite doable with a 1U. It gives rotation slow enough to get a few sensor readings per turn, which allows for correction of any tumbling that might develop.

For torque, magnetotorquers. Just a square coil per face. It's very simple to build, and it will provide enough torque both to spin up the cube initially, to adjust rate of rotation if necessary, and to re-orient axis of rotation by having it precess around the magnetic field. It's simple, cheap, has few things that can go wrong with it, and we can do everything we need to with it.

I have some questions/concerns how to realize the experiment.

How do you think to sustain the pressure of your experiment?

Good question. Depends a lot on duration we can plan for. If it's a low altitude launch with cheap hardware, it won't live past couple of weeks. Seal-and-forget might be the way to go there. Pressure will drop, but within acceptable levels during duration.

If we get at least an ISS orbit launch, and especially if we can get the electronics that will survive for many months if not years, then we definitely need a way to sustain the pressure. It'll have to be a gas generator of some sort. It'd be nice to find a fluid with vapor pressure ~1bar in relevant temperature range which is also inert and non-toxic, but that might be asking for too much. Otherwise, perhaps something that can be decomposed into harmless gasses at high temperature. Again, preferably a liquid. I'm going to look at some options.

Of course, before settling on something specific, it'd be nice to build a prototype of the eco chamber and see how long it holds pressure.

On your interplanetary journey you have disturbances by solar wind and radiation pressure. You have burn errors, that are small (impossible to avoid) while burning, but they matter big in the end. Also the atmospheres are highly dynamic and the aerobreaking maneuver therefore highly uncertain. For example the upper atmospheric density depends on the solar activity, which will change during your mission time.

For anything that leaves Earth system, we'd definitely need serious external help with tracking. It should be possible to get some radio telescope time via some education outreach programs. I've done some basic experiments while in school that way. That would, at least, take care of the communication, as well as some rough telemetry. For more precise telemetry, DSN might be the way to go, yes. But I have no idea how hard it'd be to get access to that. On approach, final corrections would have to be done by visual localization. That's probably the only way to get precise enough fly-by with something like that, and certainly the only way on aerocapture. Aerobraking would also require adjustable airbrakes, weather data from target body, and a good deal of luck.

In any case, this is something with a whole different sort of budget. We'll see how much money we can get. Maybe even look at doing a second mission once the first one is successful to see if we can get better funding. But it's good to have ideas like that in mind, to always have a bigger, better goal out there.

[Nicholander]

One: I can't connect to the internet sometimes (I'm in vacation in Australia and i'm sometimes in houses with no internet), so don't expect me to be able to post all the time until I say i can.

Two: Did any of you notice my thing about the Orbiter thing?

[Aethon]

This is gonna happen.

The Kerbal Space Program Space Program. (KSPSP)

So what are you saying- that were redundant- that we repeat ourselves- that we state things over and over again??

[christok]

I've been thinking about the experiment. I'm still really uncomfortable with exposing it to direct sunlight. Here's what I have in mind:

- We divide the experiment into two or three equal-volume concentric rings. Each of these will experience different levels of artificial gravity.

- Our experiment should be to sprout some seeds. I'm thinking of the bean-sprouting experiment for kids, which is simple and gives us lots of educational potential. We can measure which plants sprout "correctly" with the root growing down (=out) and the stem up (=in), as well as the growth rate. These should be affected by the gravity in each ring.

- Coriolis effects may also cause the plants to grow at an angle. This would give us some cool photographs for public outreach/education.

- Because we don't want to sprout the seeds weeks before launch, we'll need some way of watering them during or after launch. I think some kind of fragile water reservoir would work well; designed to break during launch. We would need an exception to put a new water reservoir and seeds in after vibration/drop testing, but I think we could motivate it successfully.

- We don't expose the experiment to direct sunlight. Instead, we have a small amount of light provided either by one or several LEDs or by reflections off the structure of the spacecraft incorporated into the design, or perhaps sunlight filtered through other spacecraft components that are semi-transparent. This not only prevents us from cooking the plants on the day side but also provides better insulation on the night side.

- The light is mainly for the camera to see the experiment, but will also allow us to observe the plants grow (and photosynthesise) beyond the initial experiment. We'll need to design it carefully so that we don't give more light to either the outer or the inner rings if we do it this way.

- We don't need a complex biosphere because the main experiment is quite short. Anything we get after that is a bonus.

- It's easy for all forum members and the general public to test the basic conditions (common seeds in a small closed space) at home.

- If we use beans, we get a plant that comes with its own nitrogen-fixing bacteria and is a food crop.

[RocketmanRower]

So if we use electrospray prop, which isn't that expensive relative to other options and I have access to through my lab at school, we could get ISP of 3500. Just lower thrust

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.

[AngelLestat]

So at every moment you need to make sure that your spacecraft components are within the acceptable temperature range.

Hi Ksat, is good to have someone with experience and knowledge in the field to guide us.

If we find that in fact some components are overheating, what we can do about it?

We can not use radiators or insultation if we dont have some attitude control with respect the sun.

Any good insultator would be a bad radiator and vice versa.

I know that this is not a easy question, but maybe there is some base designs to help us deal with this without much knowledge in thermal engineering.

You probably already have seen this document, but to be sure:

Cubesat Requirements

http://cubesat.calpoly.edu/images/developers/cds_rev13_final.pdf

I dint, thanks. There is a doubt that I have with respect to this.

I saw many videos where cubesats are inspected in special facilities which commonly work for the launch provider.

You have an idea or estimate of this inspection and testing cost?

For a missision of less then a month radiation should not be that harsh, but some shielding should be implemted. In general sensitive parts are placed in a spacecraft, where it is shielded by other less sensitive parts. Also from your orbit you can expect an increased radition flow from prograde direction (electrons).

Yes, we can keep our cubesat-tether normal to earth surface, but I am not sure yet how control the spin on that axis.

I will make a research to know if there is another passive way to achieve that.

Then know how to distribute the electronic load-shield is simplified.

It depends on your mission. If your starting orbit is high enough, you might be able to feed on your orbit energy until you start reentry. Therefore no other power generator would be necessary. If you plan a longer stay solar cells are needed and you would be able to maneuver in earth orbit.

This altitude difference may increase the launching cost mostly due to possible lifespan as debris in case the tether system fails?

But one major concern. The elecitrical power by a tether is big and a cubesat is small, if you go for the tether you need to make sure you can survive the power output of the thether.

Resistors would produce a lot of heat so probably a shorter tether is the easiest solution when power is to high.

Yeah,I will try to contact anyone who is studying this, I know that there is already software simulation to calculate space tethers, I will ask how much they cost or if there is a free version to students.

Also there is the Nasa issue with this experiment, when apparently they receive a voltage peak out of their predictions.

For torque, magnetotorquers. Just a square coil per face. It's very simple to build, and it will provide enough torque both to spin up the cube initially, to adjust rate of rotation if necessary, and to re-orient axis of rotation by having it precess around the magnetic field. It's simple, cheap, has few things that can go wrong with it, and we can do everything we need to with it.

You would use some kind of tether (or the same conection wires) to increase the long and quality of the gravity simulation?

Because if you dont do it, the gravity in the plant root would be higher than the plant top.

You plan to use solar light to the plant growth or artificial? Because the intermittence due to rotation can be an issue too.

Depends a lot on duration we can plan for.

That is something that we need to ask to Mary Musgrave.

The plant species chosen, the time needed to growth, the light and conditions needed. All cubesat components depends on that.

It'd be nice to find a fluid with vapor pressure ~1bar in relevant temperature range which is also inert and non-toxic, but that might be asking for too much. Otherwise, perhaps something that can be decomposed into harmless gasses at high temperature. Again, preferably a liquid. I'm going to look at some options.

I know what you mean, but so many variables needs to fix and so few liquids to choose.

The positive side is that it would not take you long time to know it.

Of course, before settling on something specific, it'd be nice to build a prototype of the eco chamber and see how long it holds pressure.

You mean test the sealed that you would use with higher pressure inside to mimic the pressure difference in space?

For anything that leaves Earth system, we'd definitely need serious external help with tracking.

As I comment in my first post, this would be an option only if launch cost fall at least 5 times or more before try to do an interplanetary mission, If this happen cubesats components cost would fall too.

Two: Did any of you notice my thing about the Orbiter thing?

What post are you talking about? You mean use orbiter as simulator?

- We divide the experiment into two or three equal-volume concentric rings. Each of these will experience different levels of artificial gravity..

Is not a bad idea, but the cost growth significantly, the space is also an issue, how much the plants needs to growth?

-------------------------------------------------------------------------------------------------

I guess we should made teams to research and give an estimation of the components/cost needed, to evaluate different mission requirements.

We can do it making extra topics, maybe new KSP field specialist will joint us.

For example I will study the electrodynamic tether approach. Who want to help me in the research?

Then K2 and others can team up to study the biologic microgravity approach.

Extra teams can joint to study different approachs. Then we go back here with numbers, good estimations and more knowledge about the experiments to compare our options. Then it would be easy to see what approach we may discard or look with more attention. Once funds are collected. We do a final choice.

[Mazon Del]

Unfortunately with doing the concentric rings approach, we really don't have a lot of space inside the cube. You might get away with having a second ring.

But the real problem with this is you have to take into account how the experiment is going to be oriented with relation to the forces the sat will be under during launch. During pre-launch you will have 1G "down" (down being predictable because of the requirements for how cubes are packaged in the P-Pod and and how that ends up relative to the launch vehicle itself). During launch you will have something like 4+Gs to deal with. So if we make a cylinder and line it with soil, half the soil is going to be trying to 'fall' with the 4+Gs, and the rest is going to want to move "sideways".

A possible solution to this is to have two trays, one on top of the other facing each other, pressed together. While pressed together there is no room for the soil to move. Once in orbit, the two split (one is anchored, the other moves) and move to opposite sides of the space. This solves the balance problem that I had been worried about (If you have one tray and you spin the sat, everything is unstable. It is how the vibrator in your phone works) and ensures the soil doesn't spray everywhere during launch. I like KSat's idea of having foil or something there on top of the soil to help keep it in position during the zero-g. This would end up being one sheet each for the two trays (sandwiched between them). What wouldn't be too hard is actually to have a single tiny motor that peels the foil material back once the craft is under rotation. I would be a little concerned with having the foil remain in place as it is an impermeable barrier which would make it more difficult for the plants to be watered.

Speaking of water, how do we intend to really do that? We will only be able to carry so much with us. My original idea for the life in a jar concept had ignored the need for continued watering simply because the type of life in a jar I was discussing was those closed loop systems that were watered once years ago and just recycle their own water/air.

Currently the list of material consumables for this mission seem to encompass the following:

Water

Carbon Dioxide

Electricity

To date I believe we have primarily discussed electricity. I have a chemist friend of mine I am going to speak toabout the CO2 problem. He might be able to suggest a safe and efficient chemical reaction that we could utilized. Say mixing two non-pressurized chemicals together? Something like that. Mary Musgrave (whom I have had difficulty in contacting. I will try more tonight or tomorrow) identified that one problem the plants get is that they suck in all the CO2 and then suffocate because there is only O2 left in the air.

[PlonioFludrasco]

Shall think about the structure, too.

I' ve seen that you can buy already assembled main structures, at a cost not below 1000$.

Could be an option to build our own, considered that the raw material (anodized Al 7075, for example) costs way less?

[K^2]

You would use some kind of tether (or the same conection wires) to increase the long and quality of the gravity simulation?

Because if you dont do it, the gravity in the plant root would be higher than the plant top.

You plan to use solar light to the plant growth or artificial? Because the intermittence due to rotation can be an issue too.

The axis of rotation would point towards the Sun. (Not necessarily directly at it, but in general direction, at least.) So illumination would simply have the 1h:30 day/night cycle (ISS orbit) due to being in Earth's shadow for half of the turn.

Tethered version would be nice to try, but that's considerably higher funding. It would require better attitude control on both the primary and counterweight. The base mission would simply have 0.5U of "cargo" space, and the entire cube will rotate. That's sufficient for 0.1G. Tethered version would allow 1G+, of course, which has advantages. For a funding++, I could even see tethered system of several trays at different G levels, with two 0.5U on the ends for control. But that'd require a 2U-3U unit that would unfold. Tricky stuff.

In the basic unit, however, we can set up several tiers of hydroponic nets. Looking at root growth of germinating seeds at different G levels would be a really cool short-term experiment. Something we can definitely do, and it would have some value. I'll see what research has been done on the subject. Plus, if the camera or even CPU bites the dust in a week, we'd already have useful data. Ideally, however, it needs to be something that would be interesting to observe for a few months, if hardware survives that long.

On your tethered drive idea, I've looked at the sizes of aluminum foil rolls available. It should be possible to get a narrow, continuous strip that's almost quarter of a mile long without having to get it custom made. It wouldn't be very strong, but barring any foo bars with attitude control, it doesn't need to be. I'm going to re-run the numbers with this in mind. This might be viable after all. It still feels like a riskier mission, but any sort of a propulsion idea appeals to me personally.

Could be an option to build our own, considered that the raw material (anodized Al 7075, for example) costs way less?

Yes. We've discussed some custom machined parts in this thread. There are definitely options there that would give us better flexibility and lower price tag.

[Mazon Del]

Propulsion ideas are quite enticing, but if we do I'd say we would probably have to abandon the idea of the life in a jar. Mostly because if we kept the budget low, we certainly wouldn't be able to do both at the same time easily. But if we had the budget and we upped to a 2-3U, we could make it work. The trick is that if we are actually going with any sort of propulsion system, then we'd have to up the budget on the rad hardened equipment, simply because we'd likely get months-years of use out of the sat.

Also, one thing to note for those who haven't read through that pdf, the cube sat is not allowed to generate additional debris, so no fairing separation type stuff going on. Propulsion exhaust is 'probably' allowed. I haven't finished reading myself yet.

[K^2]

Gaseous exhausts are definitely allowed. There are plenty of propulsion systems designed specifically for cubes.

And yes, the tethered ideas are higher budget, and most likely exclusive with bio experiment. I have nothing against doing theoretical work for both until we have some sort of an idea on the budget, however.

[Mazon Del]

Indeed, nothing wrong with that.

Though admittedly it would be quite fun to lob a life-in-a-jar (of my original low maintenance type) out into a solar orbit and take the world record for most distant confirmed life away from Earth. Just occasionally getting back images from the satellite as it floats around, its own little world made by us. ^^

Wouldn't that be a fun record to take from NASA?

Edited July 26, 2014 by Mazon Del

[Nicholander]

The orbiter thing I was talking about was to do what ESRO did in that youtube video, making the CubeSat in Orbiter and showing at as a thing to get more attention, as visualizing it would certainly raise interest in it.

Oh, and about the teams. I would be more a electrical main systems guy I guess you could say, I mean things like MPUs, CPUs, maybe the cameras, the memory/hard drive, etc. So basically, non-Biological stuff.

[K^2]

Got any experience coding in machine language and/or assembly?

[KSat]

Hello K^2,

I don't actually think 1G is a reasonable goal. I've mentioned before that 1m/s² is quite doable with a 1U. It gives rotation slow enough to get a few sensor readings per turn, which allows for correction of any tumbling that might develop.

I'm sorry that I was not able to read all the previous posts and you needed to repeat yourself. 1m/s^2 sounds better to me.

For torque, magnetotorquers. Just a square coil per face. It's very simple to build, and it will provide enough torque both to spin up the cube initially, to adjust rate of rotation if necessary, and to re-orient axis of rotation by having it precess around the magnetic field. It's simple, cheap, has few things that can go wrong with it, and we can do everything we need to with it.

Yes, I think magnetotorquers are the way to go for LEO cubesats. On our MIRKA2 Mission we are also going to use them.

It'll have to be a gas generator of some sort. It'd be nice to find a fluid with vapor pressure ~1bar in relevant temperature range which is also inert and non-toxic, but that might be asking for too much. Otherwise, perhaps something that can be decomposed into harmless gasses at high temperature. Again, preferably a liquid. I'm going to look at some options.

Liquid CO2 could be an option, it would degas itself, sustain pressure and for plants a 100% CO2 atmosphere is like fertilizer. Liquid nitrogen could be an option but is pretty inert and wouldnt do much. Something I am not quite sure about. It could be that if they plants are very industrious and they convert all the CO2 , that in the end a nearly 100% O2 atmosphere is present, you might have created a serious fire hazard. Which mould make for some nice final pictures I guess.

Opening a valve could also be tricky for cubesats. Because it is often a launch requirement that gas tanks need to be physically sealed and are then in orbit opend by pyro valves (small explosives that punch through the seal). Currently no pytotechnics are allowed for cubesats.

For more precise telemetry, DSN might be the way to go, yes. But I have no idea how hard it'd be to get access to that.

Everthing that belongs to NASA is very hard to get access to. Maybe if some of the americans knows some professorsfrom their universities that have direct connections to them.

On approach, final corrections would have to be done by visual localization.

I doubt that this is possible. It is more likely that you will approach way to far off than your propulsion can provide to correct in the last moments. What do you mean by visual localization? If you mean startrackers, to calculate your position it is possible while correcting all the way. But if you mean looking where your target is and then propelling there, then it is nearly impossible.

Gaseous exhausts are definitely allowed. There are plenty of propulsion systems designed specifically for cubes.

Pressurized tanks are the problem here. The cubesat requirements allow only for pressures of 1.2 bar. So the gas needs to be generated from storing liquids or solids.

Electrospraythruster from Busek uses a ionizable liquid it has low thrust but high specific impulse.

Other electric options could be the Clydespace pulsed plasma thruster but is probably off budget.

Isobutane could be used as a cold gas generator.

Or if you want it combustable you might go for water electrolysis.

Got any experience coding in machine language and/or assembly?

Sorry I do not have any experience in that yet.

Cheers,

KSat