Ultimate Steve

Cubesat to the moon?

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I'm not really good at starting posts, but I'll try with this one. Basically, I got bored at school today and decided to do some Delta-V calculations. Ideally, a 3u cubesat weighs 4kg. This engine weighs just over a 1kg and can have a specific impulse of up to 1300 n-sec. According to This delta-v calculator, if the cubesat weighs 4kg fully loaded with fuel and 2kg empty (leaving 2kg for fuel (I'm not sure that is the right fuel, but the right one is probably similar)) gives the said cubesat about 8.8 kilometers per second of Delta-V. This is theoretically enough to reach Lunar Orbit.

First off, I know that you can get a cubesat to the moon by hitching a ride on a larger rocket, but none are scheduled to go there for a while. The question I had asked myself is if you could reach the moon starting from LEO.

Space wise, the said fuel has a density of 1.38 g/cc. 2kg of it would be about 1500ml (or cc) and would take up 10*10*15cm of space. A 3u CubeSat measures 10 by 10 by 34 cm (I think). The engine takes up a 6cm long space. Ideally, the propellant would take up a space 15cm long (although it would actually be longer, because of the volume of the tanks). This leaves around 13 cm of usable space left.

So, now we know we can reach the moon with a CubeSat. However, my question is: "Is it possible to fit the necessary systems for a CubeSat in a 10*10*13 space and have it weigh less than about 0.8kg?" By necessary systems, I mean electrical power, comms, orientation, computers, tanks, etcetera.

So, can it be done?

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Yes.

Why? Because the miniaturization of technology is making it possible to make extremely small electric and computer equipment, just look at Project Starshot.

So, assuming you have the smallest, lightest comms, computers, and electric equipment, it can be done.

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The biggest restraint on cubesat engines is that you can't have volatile chemicals and pressurized gas on many cubesat launches. Looking at the engine, it runs on ionic liquids, which are pretty non-volatile. I'm not sure about the density and storage requirements. Could you fit that into. 3u cubesat?

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There are actually secondary payload opportunities for lunar missions, China Great Wall are offering some spare capacity from the Chang'e missions. They already had a commercial payload (Luxspace's M4) on the Chang'e 5 T1 mission in 2014, and they're flying another Luxspace secondary in 2018 (either on Chang'e 5 or the relay sat for Chang'e 4). The first payload was a simple comms unit attached to the upper stage, but the second is supposed to be an independent microsat, with enough propulsion capability to enter lunar orbit.

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@Ultimate Steve : Of course it is possible for a Cubesat to go to the Moon. Unfortunately, as usual, it's just a matter of how much money you can spend for this mission. For instance, The busek ion thruster that you mention in your post, seems far too big, even for a 3U cubesat. 1 kg out of 4 kg available ! You also need to keep enough for solar panels, battery, transmission, video camera, and positioning (star tracker or something else). 

You should have a looks at Accion Systems (http://www.accion-systems.com/)

The MIN-0 datasheet : http://static1.squarespace.com/static/5446faa2e4b025843cfc6731/t/56b89ec537013bd1851a9ba4/1454939846248/MIN-0_FlySheet.pdf

The MAX-1 datasheet : http://static1.squarespace.com/static/5446faa2e4b025843cfc6731/t/5626959ae4b0d3deeaf7d293/1445369242056/MAX-1_FlySheet_02.pdf

The TILE-1 datasheet : http://static1.squarespace.com/static/5446faa2e4b025843cfc6731/t/56b89b839f72662e5f8f460d/1454939011707/TILE_FlySheet_v2.pdf

You should also read this : http://web.mit.edu/aeroastro/labs/spl/research_ieps.htm

Of course, You will need to put several thrusters to reach the Moon, but they are not that heavy.

The final problem you will have will be to land on the moon safely. That is another challenge ...

 

Edited by Mecatroid

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I think it might be a while before we see a cubesat deployed at LEO perform an transfer to lunar orbit under its own power. That said there are several lunar cubesat projects underway: NASA is offering (3?) ride share opportunities on the SLS shakedown flight EM-1 in 2018. A number of teams are competing for these slots, among teams from UCSD, Cornell, MIT. There's alot more information herehere and here. Most are definitely bigger than 2U, the UCSD Triteia is a 6U for instance. AFAIK these will be the first ever cubesats to leave Earth's sphere of influence.

I agree that subsystems design for ops beyond LEO is an interesting challenge. I'm guessing that these cubesat will have relatively tiny link budgets (S-band on omni-directional antennas, probably very small transmit power budgets), they will need very large tracking antennas here on Earth. Rad-harding and fault-tolerant computing requirements will no doubt increase in cis-lunar space and beyond as well.

secondary_payloads_infographic_v6.jpeg

Edited by architeuthis

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15 minutes ago, architeuthis said:

I think it might be a while before we see a cubesat deployed at LEO perform an transfer to lunar orbit under its own power. That said there are several lunar cubesat projects underway: NASA is offering (3?) ride share opportunities on the SLS shakedown flight EM-1 in 2018. A number of teams are competing for these slots, among teams from UCSD, Cornell, MIT. There's alot more information herehere and here. Most are definitely bigger than 2U, the UCSD Triteia is a 6U for instance. AFAIK these will be the first ever cubesats to leave Earth's sphere of influence.

All the SLS slots are 6U, six have already been selected by NASA. They should launch after the MarCO communication relay sats on InSight, which are also 6U.

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SSTL and Goonhilly Deep Space Station started to promote a commercial and lower cost ride to the Moon under ESA partnership for cubesats. It will provide communications back to Earth. You can find more details at: http://www.goonhilly.org/lunar and if you are interested, there is an Expression of Interest form. 

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