Submitted via IRC for takyon
A Silicon Valley startup developing electric propulsion systems for satellites has raised $10 million and added the billionaire founder of LinkedIn to its board.
Apollo Fusion announced the $10 million Series B round July 11, bringing the total the company has raised to date to more than $18 million. The round was led by venture fund Greylock Partners, with one of the fund's partners, Reid Hoffman, joining the board.
Apollo Fusion will use the funding to scale up manufacturing and testing facilities for its electric propulsion system, called the Apollo Constellation Engine (ACE). The company believes that ACE is well-suited to serve the growing demand for smallsats with onboard propulsion.
Source: Electric satellite propulsion company raises $10 million
(Score: 1) by anubi on Tuesday July 17 2018, @05:25AM (9 children)
Xenon Ion engine?
"Prove all things; hold fast that which is good." [KJV: I Thessalonians 5:21]
(Score: 2) by c0lo on Tuesday July 17 2018, @05:46AM
TFA
My guess? They may be using a multiple ionized element, perhaps stored as a compound substance (denser than the liquefied gas form? The decomposition of which may let the element already ionized instead of expending energy to eject those electrons from a neutral atom first, accelerate them later?)
https://www.youtube.com/watch?v=aoFiw2jMy-0 https://soylentnews.org/~MichaelDavidCrawford
(Score: 2) by realDonaldTrump on Tuesday July 17 2018, @05:50AM (7 children)
I looked on LinkedIn. Because Reid Hoffman started LinkedIn. And Benjamin Longmier, one of the guys that started the Company -- started Apollo Fusion -- says something about Xenon in his profile. And he's the CTO. linkedin.com/in/longmier [linkedin.com]
(Score: 1) by anubi on Tuesday July 17 2018, @06:19AM (6 children)
I looked at your link.
He mentioned iodine as well, but frankly, I am concerned about the chemical reactiveness of iodine with its container and valving, whereas xenon is pretty damned inert and doesn't attack its container. The craft is going to have to live with a bellyful of this stuff for several decades.
"Prove all things; hold fast that which is good." [KJV: I Thessalonians 5:21]
(Score: 4, Insightful) by c0lo on Tuesday July 17 2018, @07:07AM (5 children)
Those will be decades spent at near zero absolute temperature - I wouldn't worry that much about storage and storing time. Besides, with a solid fuel, you don't need pressurized tanks, borosilicate glass will do.
Reactivity may be a problem when bringing it at higher temperatures, but then you extract minute amount of the substance. I imagine some electron beam hitting the reservoir and vaporizing/ionizing the material straight out of the "fuel tank" and strong magnetic fields to keep the ions confined until they get to acceleration chamber will eliminate "valving".
Look, sodium is more "caustic" than iodine, but you still have those yellow sodium street lamps [wikipedia.org] in use everywhere.
https://www.youtube.com/watch?v=aoFiw2jMy-0 https://soylentnews.org/~MichaelDavidCrawford
(Score: 4, Informative) by Immerman on Tuesday July 17 2018, @12:56PM (4 children)
Not even close to absolute zero - anything in orbit is getting at least as much sun as we do here on the surface, and possibly twice as much depending on the height of the orbit.
The ambient temperature of space itself may be close to absolute zero - but anything *in* space is going to reach thermal equilibrium based on how fast it can radiate the solar energy it's absorbing. As a rule of thumb, anything closer than the asteroid belt can't even keep water frozen if it's exposed to sunlight.
(Score: 2) by c0lo on Tuesday July 17 2018, @11:53PM (3 children)
Just make the satellite all shiny outside and all black inside and insulate the iodine in a dewar flask. In about half a year (gut feeling) thermal radiative losses will bring the fuel close to zero.
In any case, the above is a pure exercise in tech pedantry, even -100C is more than enough to keep iodine reactivity to a safe to ignore level.
https://www.youtube.com/watch?v=aoFiw2jMy-0 https://soylentnews.org/~MichaelDavidCrawford
(Score: 2) by Immerman on Wednesday July 18 2018, @03:28PM (2 children)
From what I can find, the average temperature of a satellite in orbit is approximately the same as it is on the ground, but with greater temperature swings (-170C to 123C from the first google link). Shininess could help, but you've got great big unavoidable heat collectors in the form of the solar panels powering everything, and heat will flow from them down the power cables if nothing else.
(Score: 2) by c0lo on Wednesday July 18 2018, @03:47PM (1 child)
As long as the radiative loss of heat from the fuel tanks is greater than the rate of heating due to direct contact, the fuel tank is going to cool down.
It may not reach into fraction of Kelvin but for sure proper arrangements can be made to have it dropped below -100C.
(e.g. no need for the power cables to reach the tank - heat the fuel when needed by electron beams. No need for the tank to be fixed using large contact brackets once in space, as an ion engine is not exposed to high accel, simple point-contact "brackets" suffice; support the tank during escape from Earth grav, then eject the massive support and keep something with minimal surface contact to the fuel tank itself).
https://www.youtube.com/watch?v=aoFiw2jMy-0 https://soylentnews.org/~MichaelDavidCrawford
(Score: 2) by Immerman on Wednesday July 18 2018, @07:42PM
Yeah, that might work, though there's a certain amount of unavoidable thermal contact in the form of the fuel line. And there's lots of active cooling techniques you could employ as well. If orbital research equipment can be held at cryogenic temperatures, I'm sure a fuel tank can be chilled to something much more moderate.
That radiant heat transfer from the tank does fall off quickly though. Radiant emissions are proportional to the 4th power of the absolute temperature - so cooling from a mild 15C (288K) to -100C(173K) means your radiant emissions have fallen to only 13% of their original levels, and the interior of the satellite will be shining back much more strongly, regardless of color. Better have a really shiny fuel tank, and a thermally insulated fuel line. Might need some more active refrigeration system to supplement it
(Score: 0) by Anonymous Coward on Tuesday July 17 2018, @07:36AM
I worked for a company that was building these in the early 90's.
https://en.wikipedia.org/wiki/Electrically_powered_spacecraft_propulsion#History [wikipedia.org]
(Score: 0) by Anonymous Coward on Tuesday July 17 2018, @01:12PM
well if "losing mass" is the problem then just ride neutrinos.
they are afterall rather "massless".
using some electrons to make some muons and having these then decay back into electrons (to be recycled)
and some neutrinos.
muons are rather massive, like 207 times electrons, so caterpillar like having the spaceship accelerator tube crawl along the beam might give a push?
if then the muon-decay neutrino beam could be made to point in one direction consistently, then
the spaceship could just ride the newton impulse of the leaving neutrinos also.
since the neutrinos are rather massless, it would not put the spaceship on much of a diet.
the other question is however, since the neutrinos are so massless and hard to detect, on what are they going to push in the universe in general, since they seem to just fly to everything? it's like trying to push on a ghost or specter?