News CubeSat to Enceladus?

[Unstung]

There's a Kickstarter project that appeared a week ago for sending CubeSats to interplanetary and possibly interstellar space.

A CubeSat would use a plasma propulsion system to constantly boost its apogee eventually and escape Earth's gravity. From the webpage's "Big Idea" section:

The future of space exploration is not limited to the conventional approach of the past with large, expensive spacecraft! Most satellites and interplanetary spacecraft launched by NASA and private industry today are the size of a car and can cost up to one billion dollars or more. CAT is a plasma propulsion system designed to fit in 1U of a 3U (or larger) CubeSat. CubeSats are a type of nanosatellite made up of 10x10x10-cm units (1U) and cost 1,000 to 10,000 times less to develop and launch than conventional satellites.

Currently, these CubeSats piggyback a ride on larger rockets, and once in space, they drift around Earth, trapped in their original orbit until they eventually de-orbit and burn up in the Earth’s atmosphere. However, CAT will extend the potential destinations of these CubeSats to way beyond Earth orbit.

We are working to complete and vacuum test a flight-qualified satellite with an integrated CAT. Through our existing partnerships with three NASA centers, the spacecraft will be launched into low Earth orbit and start its climb into deep space. The CAT engine is being developed at the University of Michigan’s Plasmadynamics and Electric Propulsion Laboratory (PEPL). Our team also includes the state-of-the-art Michigan Exploration Laboratory (MXL), which has over six years of experience building and flying CubeSats.

Initial CAT engine testing will be performed in our lab on the ground and then in low Earth orbit (LEO) to validate the CAT engine's performance and physics models developed by our team. Once these tests are completed, we will perform a series of spiral-out flight maneuvers to climb to higher and higher altitudes in order to escape the Earth.

 

[RisingFury]

I don't know... at $200 000, it seems a little low...

And don't count on any effective solar power production at Saturn. It's bad enough at Mars, horrible at Jupiter and with the power that such a thruster needs, next to impossible at Saturn. No power, no thrust.

 

[Alfastar]

Well, its not really a smart project. I mean, its goal is to go to interplanetary space with the ion engine it got, and going to leave our solar system. However, its only using tiny solar panels and batteries. It don't got any RTG on it, and how the design looks, this spacecraft is already dead when its passing Mars orbit. So a really good scientific goal it don't got.

So, don't spend you money on it.

 

[Unstung]

And don't count on any effective solar power production at Saturn. It's bad enough at Mars, horrible at Jupiter and with the power that such a thruster needs, next to impossible at Saturn. No power, no thrust.

Of course using such propulsion methods so far away from the sun (given the inverse square law, Saturn receives ~1% light Earth does) is extremely impractical. However, why not use gravitational assists after the spacecraft is able to escape Earth orbit to get to a destination in the outer solar system? It may be impossible to secure a plutonium power source for a small private spacecraft and install a bulky thermocouple (would something the size of a radioisotope heater unit work?), but its instruments may require very little power. Solar cells may provide enough power for a spacecraft to operate at Jupiter or Saturn (even solar-powered Uranus missions have been proposed), but an interstellar mission would clearly be impossible. Due to the lack of solar energy, only flyby missions of the gas giants would be possible. The proposal still has potential if the spacecraft are confined to explore the inner solar system.

 

[RisingFury]

Of course using such propulsion methods so far away from the sun (given the inverse square law, Saturn receives ~1% light Earth does) is extremely impractical. However, why not use gravitational assists after the spacecraft is able to escape Earth orbit to get to a destination in the outer solar system?

Getting there isn't the problem! Stopping and entering orbit once you get there is the problem.

While the engine can eject you from Earth's orbit, you'd have to have another engine with you to stop you once you get there. That means double mass...

It may be impossible to secure a plutonium power source for a small private spacecraft and install a bulky thermocouple (would something the size of a radioisotope heater unit work?), but its instruments may require very little power.

Electric engines require in the range of 1 kW power minimum and a typical RTG generates in the range of 100 W. These RTGs are also very massive, given the density of Plutonium...

Solar cells may provide enough power for a spacecraft to operate at Jupiter or Saturn (even solar-powered Uranus missions have been proposed), but an interstellar mission would clearly be impossible. Due to the lack of solar energy, only flyby missions of the gas giants would be possible. The proposal still has potential if the spacecraft are confined to explore the inner solar system.

A solar powered mission to Jupiter only exists because our supply of RTGs is (thankfully, ironically) running out. It's become cheaper to send a solar powered mission there, than one powered by a RTG. While a mission to Saturn might marginally work, I doubt one to Uranus or Neptune would using current solar cell technology. Even with 100% efficiency, the inverse square law just kills power... We need lighter cells for it to make sense.

 

[malisle]

Here are some irradiance values just to get the scale of things. They may be a little off since they are not mean values.

Mercury: ~10 kW/m^2
Venus: ~3kW/m^2
Earth: ~1.5kW/m^2
Mars: ~0.6 kW/m^2
Jupiter: ~50 W/m^2
Saturn: ~16 W/m^2
Uranus: ~4.2 W/m^2
Neptune: ~2 W/m^2
Pluto: ~1 W/m^2
Eris: ~0.15 W/m^2 (@apoapsis)

 

[Unstung]

Getting there isn't the problem! Stopping and entering orbit once you get there is the problem.

While the engine can eject you from Earth's orbit, you'd have to have another engine with you to stop you once you get there. That means double mass...

As I mentioned later on in my post, only flybys of the gas planets would be possible. However, would it be reasonable to attempt using gravity assists so a spacecraft could fly directly under the geysers of Enceladus with little chance for course corrections? On the other hand, the Kickstarter claiming a CubeSat with such propulsion could orbit Europa doesn't sound right... but the page says that the engine provides "p to 2 mN thrust for 10W (20mN for 100W pulsed)", however the specs say that "20 W of power produced from deployable solar panels" in Earth orbit. It's proposed to last a reasonable amount of time for an outer planet mission with an "[a]nticipated lifetime beyond Earth: 10 yrs (battery lifetime)". But compared to something like the battery-powered Huygens or ESA's EDM lander, that's really long.

Electric engines require in the range of 1 kW power minimum and a typical RTG generates in the range of 100 W. These RTGs are also very massive, given the density of Plutonium...

I was referring to how much power the spacecraft would need to run its instruments far away from the sun, not the engine.

 

[malisle]

I was referring to how much power the spacecraft would need to run its instruments far away from the sun, not the engine.

Probably not very much during the transit since there would be some sort of hibernation to reduce power consumption. Without foldable solar panels 10x10x10 cm cubesat has a surface area of 0.01m^2 exposed to sun if properly oriented, which would give out 0.045W at Saturn with panels that have a generous 30% efficiency. With 10 times that area it would still be less than half a watt.

Also, how would it communicate with Earth? For comparison, Juno and Cassini have high gain antennas 2 meters in diameter. Only way would be piggybacking communications to real orbiter such as Cassini and have it forward it back to Earth.

 

[Unstung]

Also, how would it communicate with Earth? For comparison, Juno and Cassini have high gain antennas 2 meters in diameter. Only way would be piggybacking communications to real orbiter such as Cassini and have it forward it back to Earth.

Galileo was forced to rely on its low-gain antenna, but it is difficult to find an answer if such an instrument would fit on a tiny spacecraft and be able to transmit data back to Earth. Nonetheless, the idea of operating a CubeSat in the outer solar system has many problems that should be obvious. It makes one wonder what these educated people from Michigan University are thinking.

PS. Cassini's high-gain antenna is actually four meters wide. It really is an enormous spacecraft that's mind-numbingly far away from Earth orbiting Saturn. It's astonishing what humans can do.

 

[boogabooga]

I don't know... at $200 000, it seems a little low...

And don't count on any effective solar power production at Saturn. It's bad enough at Mars, horrible at Jupiter and with the power that such a thruster needs, next to impossible at Saturn. No power, no thrust.

They didn't say anything about using this as deep space propulsion. It seems they just expect to use this to attain escape velocity & C3 from earth orbit.

Having said that, the cubesat would have no mid-course correction ability.
I also would question how much of a scientific payload would fit on a cubesat.
Then there is the already mentioned communication problem.

Perhaps the best we could hope for is for it to be used as a sort of academic outreach where schools/interested parties can piggyback cubesats on real launches and someday get back something like a cell phone photo of Jupiter or Saturn that was taken close enough to just image the red spot or the rings and see the moons as tiny points of light.

Or perhaps we are all failing to think outside the box. What if this is so much cheaper than say Cassini that we can send dozens, or hundreds of these things out there for a fraction of the cost. What if some of the problems could be solved by swarm tactics?

What if instead of an ultra precise fly-by, we swarm the target with enough cubesat probes that there is a high probability that one gets close enough? What if we improved navigation by timing the signals between swarm members and minimized uncertainty like GPS? (assuming they could do something about it at all.) What if we set up a deep space communication network of cubesats that could use their weak transmitters to relay between each other and back to earth through a chain? What if we do inverse slingshots to the gas giants so the cubesats could recharge and transmit data when they got back to the inner solar system?

Lets not dismiss it out of hand because it doesn't look like Voyager or Cassini.

 

[fsci123]

They didn't say anything about using this as deep space propulsion. It seems they just expect to use this to attain escape velocity & C3 from earth orbit.

Having said that, the cubesat would have no mid-course correction ability.
I also would question how much of a scientific payload would fit on a cubesat.
Then there is the already mentioned communication problem.

Perhaps the best we could hope for is for it to be used as a sort of academic outreach where schools/interested parties can piggyback cubesats on real launches and someday get back something like a cell phone photo of Jupiter or Saturn that was taken close enough to just image the red spot or the rings and see the moons as tiny points of light.

Or perhaps we are all failing to think outside the box. What if this is so much cheaper than say Cassini that we can send dozens, or hundreds of these things out there for a fraction of the cost. What if some of the problems could be solved by swarm tactics?

What if instead of an ultra precise fly-by, we swarm the target with enough cubesat probes that there is a high probability that one gets close enough? What if we improved navigation by timing the signals between swarm members and minimized uncertainty like GPS? (assuming they could do something about it at all.) What if we set up a deep space communication network of cubesats that could use their weak transmitters to relay between each other and back to earth through a chain? What if we do inverse slingshots to the gas giants so the cubesats could recharge and transmit data when they got back to the inner solar system?

Lets not dismiss it out of hand because it doesn't look like Voyager or Cassini.

I remember reading about a similar concept several years ago. Except it was slightly more ambitious. I think it required the use of several thousand small postage stamp sized sensors which would acquire velocity by interacting with magnetic fields. They were designed to travel to the Jupiter System and due to their small size, they would be able to impact moon surfaces and enter the Jupiter atmosphere without damage.

 

[boogabooga]

Interesting.

But even grains of dust burn up when they enter an atmosphere or collide with a surface.