DARPA making low-hanging satellites that use air to move

DARPA is on the verge of reaching a new low - an orbital one - as the Defense Department's research arm moves its Very Low Earth Orbit (VLEO) Otter satellite program into the production phase.  The Otter Program is moving along to phase 2 with the award of a $44 million contract to Florida-based Redwire, the company announced …

[Alan Mackenzie]

How can this work?

Just where does the energy come from to ionise the air the satellite will be passing through? That would appear to require fuel of some sort.

[Jim Mitchell]

Re: How can this work?

Solar?

[Anonymous Coward]

Re: How can this work?

It doesn't come from anywhere. It's imaginary magic coming from a 2019 Will Smith movie, yet again.

[Anonymous Coward]

Re: How can this work?

It'll be powered by a big nuclear reactor, some distance away, with wireless power transfer.

Might not be the most efficient use of the available fusion material, but that power is in abundance at those altitudes, so shouldn't cause an issue.

[Christoph]

Re: How can this work?

It is presumably solar powered, giving effectively unlimited lifetime.

However there is an obvious problem.

The more power you need, the bigger the solar panels have to be.

The bigger the panels are, the more aerodynamic drag there is.

The more aerodynamic drag, the more power you need.

This will require careful balancing!

[Anonymous Coward]

Re: How can this work?

Okay, hear me out. We shape the solar panels like wings to generate lift.

[munnoch]

Re: How can this work?

Feels like it must violate some physical conservation law.

[Vikingforties]

Warp factor 4 Mr Sulu!

Please tell me it has Bussard Collectors!

[that one in the corner]

Re: Warp factor 4 Mr Sulu!

Really hope that we are not going to have Bussard Ramjets in VLEO; as Mr Niven pointed out, fusion drives make for very nice weapons.

[MachDiamond]

Re: Warp factor 4 Mr Sulu!

"fusion drives make for very nice weapons."

The Kzin certainly learned that lesson.

[I ain't Spartacus]

Re: Warp factor 4 Mr Sulu!

They're not using a bussard collector. It's just your common-or-garden fuel scoop.

Nice simple technology. The only problem is when you accidentally crash into someone's escape pod, and now you have a cargo of slaves and a criminal record.

[Anonymous Coward]

That's awesome. I agree the entire foobly hunter college high school Chinese movie from 1996 empire should be defunded also. Thanks for the heads-up. :)

[Paul Crawford]

Generally very low orbit birds do not have a good repeat time on target, the orbit and narrow swath of the sensor gives good resolution of a small area. However, if cheap enough to do many, or if (as under discussion here) you can afford to use propulsion to modify the orbit, then you can have it returning soon-ish* to see the same area.

[*] changes to along-track timing (and resulting longitude when orbit shifts w.r.t rotating Earth) are fairly cheap, but modifying the inclination is a huge drain on engine capacity.

[DS999]

If they are small/cheap enough you can always have another one "coming around" before the orbit of the last one takes it too far off station. That seems like a more cost effective solution than spending a lot of money on one able to maximize its on station time.

[that one in the corner]

Air breathing electric-powered devices that go around the world

Between Otter at the top of the range and Solar Impulse* at the bottom, when do we stop calling them satellites and start calling them aeroplanes?

* okay, they had trouble making uninterrupted circumnavigations, but come on, the man is called Piccard, that has to count for a few bonus points.

[jdiebdhidbsusbvwbsidnsoskebid]

Re: Air breathing electric-powered devices that go around the world

"when do we stop calling them satellites and start calling them aeroplanes"

An aeroplane is one that stays up due to aerodynamic lift. That's the definition of space (ie the Karman line): the altitude at which the speed required to maintain aerodynamic lift reaches orbital speed.

[MachDiamond]

Good luck

The atmosphere breathes so the density in the upper reaches can vary a lot.

Of course, the sorts of things DARPA works on are mostly intended to kill people so there's no limit to how much the government will pay for it and there's no need to show a profit.

[Catkin]

Re: Good luck

The point of the propulsion is to overcome atmospheric drag. If the atmosphere is thinner, what do you think that might do to the demands on the propulsion system?

Also, DARPA projects can benefit humanity as a WHOLE. GPS being made accessible to all, for free, in the wake of the KAL007 tragedy being a prominent example.

[Catkin]

Re: Good luck

Apologies for the all caps

[that one in the corner]

Re: Good luck

> DARPA projects can benefit humanity as a WHOLE. GPS...

There was an earlier project, technically ARPA rather than DARPA, something to do with - fishing? Well, nets of some kind. Anyway, lots of people seem to like it.

[ben kendim]

They must surely have done an environmental impact study, right???

Extremely rarefied atmosphere... You suck it in, ionize it and shove it out at high speed behind you... What could go wrong?

I get it, big sky, a few small satellites, not many ion contrails... That environment is probably already chuck full of ionized Ozone... I guess???

But, I would love to see if someone seriously did a study to show that...

[Bebu sa Ware]

Re: They must surely have done an environmental impact study, right???

You suck it in, ionize it and shove it out at high speed behind you... What could go wrong?

If you suck in neutral gas molecules and atoms, ionize them (strip electrons from them) and accelerate the ionized gas out the back you are going to accumulate a fairly decent negative charge which is going to make the accelerating stage increasingly harder.

That part of the atmosphere isn't exactly a tranquil void as I understand extreme terrestrial electrical storms can extend up to these altitudes (sprites?) which could easily affect VLEO satellites - more so if they were highly charged, I suspect.

I can imagine an ion thruster might be designed that recombined the stripped electrons with ionized gases after the acceleration phase - a bit like an after·burner or catalytic converter. :)

[midgepad]

Canyon* apart, electron beams are easy

Electron guns are easier than ion guns, I think.

For a trivial thrust, streamlining, convenience, and reference Puppeteer engineering you might make it parallel to the ion beam.

Crossing the beams would suggest misalignment, and a reduction in effect.

* The Kzinti held it. The bottom of the Canyon continued to hold some.

[cb6]

It could be the first perpetual motion machine to get off the desk.

[Natalie Gritpants Jr]

My local already has a perpetual motion machine. There's a fan that sits on the wood burner that just keeps spinning. No wires, no batteries, just magic.

[Little Mouse]

Wood burners are like mini black holes. You drop a bit of mass in them and get bathed in toasty radiation.

(And WTF is the story with those fans that people think are blowing the hot air around? They can't work, can they? Sure, it'd be nice to have the warm air forcibly propelled into the room somehow, but the blades are only spinning because the hot air is pushing on them, not the other way around, Shirley?

Can anyone correct me on that?)

[headrush]

Google it?

Wood burner fans work by converting heat into electricity using a Peltier module, which is a thermoelectric device. The fan's base is placed on the hot stove, and this heat is transferred to the module. As the base gets hot while the top (often with a heatsink) stays cooler, the temperature difference generates an electrical current that powers the fan's motor and blades. This process is self-powered and doesn't require any external batteries or mains electricity, making it an energy-efficient way to circulate warm air and heat a room more evenly.

No one said it was free energy, it's using the existing output from the stove to drive the fan.

[Uncle Slacky]

Townsend Brown would be proud

Looks like an actual application of the "Biefeld-Brown effect"* in space at last (not counting IVO**)!

*https://en.wikipedia.org/wiki/Biefeld%E2%80%93Brown_effect

**https://ivolimited.us/

[hammarbtyp]

Whats the difference between a LEO and a VLEO sattelite?

The VLEO is a little 'otter

[fishman]

Wonderful

Another place to stick a massive constellation of satellites.

Just Fkn Wonderful.

[Spherical Cow]

Re: Wonderful

If they are switched off or if they malfunction they will de-orbit in just days/weeks due to atmospheric drag. Not really a problem.