KSP Community CubeSat

[Mr Shifty]

I'm an engineer. I guess an interplanetary mission sounds out of bounds. I suspect that $100k is a laughably small amount for this kind of mission, though maybe I'm wrong. You'd need long term tracking and communications infrastructure, equipment that can survive hard vacuum, intense temperature variation, exposure to solar radiation events, etc. You'd have to have attitude control, redundant backups, precision guidance, long term power solutions, etc. India's Mangalyaan launched last year for about $75 million, and it was the cheapest interplanetary mission ever launched. I think a LEO mission is a perfectly reasonable, achievable target which would still be pretty exciting.

It might be interesting to see what we could do with a Raspberry Pi.

[Nicholander]

I've made this "Early Phobos lander ideas" thing in MS Paint.

Derp. I just realized i forgot to draw the heatshield for the Mars aerobrake.

Edited July 15, 2014 by Nicholander

[Whirligig Girl]

ESTES MODEL ROCKET capslock on

[Nicholander]

Fine GregroxMun, fine:

Though seriously GregroxMun, my other MS Paint diagram is more important.

[Aethon]

I bet these guys (or guys like them with other, small payloads) would love to test this in space, maybe even help with finances... MIT students might help us qualify for a free ride.

http://web.mit.edu/setg/SETG/Projects/Projects.html

[Nicholander]

Nice find Aethon!

On an unrelated note, i was looking at the Busek CubeSat propulsion linked to earlier, and what do you think of the propulsion systems? They seem a bit low delta-v, but were probably only gonna do LEO for our first mission.

[mythic_fci]

If we do make a Phobos lander, here's my diagram. Almost everything uses commercially-avaliable things, such as the main processing unit using off-the-shelf CPUs and storage mediums. (Yay for technical terms!)

[Nicholander]

Excellent! Though i see that you would need 3 or more landing legs, OR you could have it so it burns so it has no velocity on the surface of Phobos, and then it gently "falls over" on it's side. This eliminates the need for landing legs, but the CubeSat could also get damaged.

EDIT: Also, someone on the previous "Pocket Spacecraft" thread (the one which eventually grew into this) said that there should be 2 MPUs (Main Processing Unit) running alongside each other, so if ones produces diffrent results then the other, it is rebooted. (This is supposed to minimize the risk of the whole mission being a failure if the MPU breaks down)

Edited July 15, 2014 by Nicholander

[BlazingAngel665]

If we do make a Phobos lander, here's my diagram. Almost everything uses commercially-available things, such as the main processing unit using off-the-shelf CPUs and storage mediums. (Yay for technical terms!)

http://i.imgur.com/Tx0ZSHQ.png

You have real problems fitting that into the available bays. The panels will need to be as large as possible if we are going with electric propulsion. If we were to use UDMH like you want to, then we run into issues launching it (its toxic stuff) as well as dV issues, We would be talking about 6u+ for even an extraordinarily minimalist Phobos lander. Also, why all the storage capacity? Transmission downlink would be a better place to spend your weight budget. Forget money, if we are trying for Phobos then weight, volume, dV, and finding a ride up to GTO is really where the challenges are.

[cantab]

A 10 millinewton engine would suffice to soft-land a 1 kilo spacecraft on Phobos. We're talking 10%(ish) Gilly's gravity here. It might be doable on electrical thrusters.

Heck, I wouldn't be surprised if lithobraking worked anyway. Escape velocity is 11 m/s, that's about 25 mph in old money. Match speeds reasonably well with Phobos to start with and go for the shunt.

[mythic_fci]

You have real problems fitting that into the available bays. The panels will need to be as large as possible if we are going with electric propulsion. If we were to use UDMH like you want to, then we run into issues launching it (its toxic stuff) as well as dV issues, We would be talking about 6u+ for even an extraordinarily minimalist Phobos lander. Also, why all the storage capacity? Transmission downlink would be a better place to spend your weight budget. Forget money, if we are trying for Phobos then weight, volume, dV, and finding a ride up to GTO is really where the challenges are.

I'm redesigning it as I type. What fuel type would you recommend? I'm still leaning for hydrazine, because although it's toxic, it by itself is very light and it removes the need for a complex dual-feed system to the engine AND an ignitor to boot.

[mythic_fci]

I wouldn't be surprised if lithobraking worked anyway. Escape velocity is 11 m/s, that's about 25 mph in old money. Match speeds reasonably well with Phobos to start with and go for the shunt.

Heh, now we're talking KSP style! If we equipped a "bumper" module to the bottom of the sat, maybe it would survive.

[BlazingAngel665]

I'm redesigning it as I type. What fuel type would you recommend? I'm still leaning for hydrazine, because although it's toxic, it by itself is very light and it removes the need for a complex dual-feed system to the engine AND an ignitor to boot.

Electric propulsion is already a must for a interplanetary go. Even using a 6u cubesat traditional propellants are barely sufficient to have a chance of lunar orbit, forget farther out. Math is forthcoming.

[Nicholander]

BlazingAngel665, I see your point about the fuel. But which would be cheaper, having large expensive solar panels and electric propulsion, or would using hydrazine be cheaper?

[BlazingAngel665]

BlazingAngel665, I see your point about the fuel. But which would be cheaper, having large expensive solar panels and electric propulsion, or would using hydrazine be cheaper?

Like I said, forget cost, for a Phobos landing you would save more money by using a 3u sat with an expensive propulsion unit then you could by using UDMH, also, LV providers will give you hell trying to handle that.

[Aethon]

Are we talking about a plane change at apogee here, to go for an equatorial orbit?

[Nicholander]

Heh, now we're talking KSP style! If we equipped a "bumper" module to the bottom of the sat, maybe it would survive.

KSP style indeed! I think that "bumper" idea is actually good, though i don't know how much the equipment in the CubeSat can take, and how much Newtons 3rd law would bounce the CubeSat back up.

Edited July 15, 2014 by Nicholander

[Nicholander]

Like I said, forget cost, for a Phobos landing you would save more money by using a 3u sat with an expensive propulsion unit then you could by using UDMH, also, LV providers will give you hell trying to handle that.

Okay, I see, using electric is better in a way. Though I still see why Hydrazine is an option.

[Rakaydos]

KSP style indeed! I think that "bumper" idea is actually good, though i don't know how much the equipment in the CubeSat can take, and how much Newtons 3rd law would bounce the CubeSat back up.

Here's a thought... by the time the probe reaches Phobos, the fuel tank will be basically empty. So we're not really going to care if we crumple the fuel tank landing, like the crash zones of an automobile.

[BlazingAngel665]

Here's a thought... by the time the probe reaches Phobos, the fuel tank will be basically empty. So we're not really going to care if we crumple the fuel tank landing, like the crash zones of an automobile.

The external structure of the Cubesat will basically be predetermined as a side-effect of the deployment system. Designing a crumple fuel system is not of significant benefit to us at these low velocities. It would expose the solar panels to undue danger at landing, since our best bet here would be to fold them in alongside the z axis of the craft to prevent damage to them in case of tipping. Landing should be done propulsive with our electric thruster if at all possible.

[mythic_fci]

This probe is a simpler version of the last. If you were to use an electric propulsion unit, the single solar panel unit would have to be big. For a monopropellant unit, the single solar panel could be somewhat smaller. The sensor and experiments arm houses the spacecraft radiator (heat exchange unit) and all the spacecraft sensors and scientific experimental equipment, somewhat like the large radial arms of the Voyager spacecraft. The engine I will leave up to you to decide, so I just wrote "Fuel tank" and "Engine" to be filled with either xenon gas and an electric propulsion system or hydrazine and a monopropellant engine.

[Nicholander]

Well, if it's electric Ion, it's fine (How does xenon gas explode?), But I don't know if it's that safe with a liquid fuel, like hydrazine.

EDIT: FCISuperGuy, i see that there's no landing legs on it. I suppose that it will "fall over" onto it's side when it lands?

Edited July 15, 2014 by Nicholander

[Teoman2]

I would love to help, count me in.

If we get a kickstarter, I will definatly donate and might pull a few strings for some extra donations

Edited July 15, 2014 by Teoman2
Spelling error

[Rakaydos]

SCIENCE QUESTION!

Can the magnets in an electrostatic thruster be used as an improvised metal detector?

[BlazingAngel665]

Math text wall

With an assumed ISP of 300 (high for UDMH) then we can begin to get an idea of how much dV our craft can have. At 1.33kg/u limit for Mass on cubesats we find that our maximum mass will be 18lbs or 8kg. We are also volumetricily limited to 10cm^3 per u. Standard fuel loads are about .75kg/u limited both by volume and mass. Therefore for dV of a UDMH system we find that we can expect about 2400m/s in dV using Vex*ln(mf/me)

So for cost:

3u Cubesat to GTO $650k

6u Cubesat to GTO $995k

by using a 3u satellite with Rf Ion engines you have a budget of $345k for that subsystem to break even.

Note, propellant costs hardly figure into these equations, UDMH is <$100/kg with electric propellants in a similar price range. The primary fund outlay is for system development and hardware. Aerojet Rocketdyne would be the preferred supplier for a Hydrazine system, due to product quality and flight legacy. None of there systems are large enough without extensive (and dangerous modifications). Quotes are available on request for all of these systems though. Busek is a decent bet for electric propulsion with several options to chose from that all fit within 1u giving us lots of volume to play with. I had the opportunity to view one of their electrospray thrusters at an Edwards AFB lab and was very impressed with the people and hardware. Our best bet here would be a rf ion engine. The ISP could approach 3000 seconds. This gives us theoretical dV of tens of thousands of m/s. This is a far better solution cost wise, and science wise. Prices also available upon request.

For a Phobos landing we are talking 1 million dollars, minimum. A small aperture space telescope in LEO could be done for less than $200k if we make sacrifices in quality. The primary outlays in this endeavor will be for the launch cost, unless we decide to get very exotic with our satellite design.

SIDE NOTE: I am assuming that the design and final assembly will come from concerned community members and not have to be contracted out, if this is not the case then our costs balloon like no other.