Idea - Aerogeneration

[EtherDragon]

Preface - Hybrid Autos...

Hybrid cars, and electric cars use Regenerative Breaking to convert momentum into electricity stored in the batery pack during deceleration. It would be cool if this technology could be used in space-craft somehow.

Idea - Aerogeneration

If, during the course or Aerobreaking or Renetry, some of the energy used to slow the ship down could somehow be captured to replenish fuel supplies. Perhaps an ultra-high-temperature ram-scoop to capture Oxygen/Hydrogen from the atmosphere on the way down. Certainly only a small fraction of the energy used in decelaration would be capturable this way - but in space every bit counts.

Imagine this scenario...

You burn hard at low efficiency to escape Earth SOI. Once out - you use a high efficiency Ion engine to head out to Jupiter.

Once near Jupiter SOI you make a MCC to skim the atmosphere of Jupiter for aerocapture. During aerocapture - you recover a bit of fuel with a ram-scoop - and some of the heat is also used to recharge your batteries.

I might have to think about including this in an implimentation of my old DG-R...

 

[RisingFury]

Oh yes! Let's put insanely heavy machinery and batteries on spacecraft, so we can regain a little bit of energy.

 

[jinglesassy]

Oh yes! Let's put insanely heavy machinery and batteries on spacecraft, so we can regain a little bit of energy.

it would only require about 3 tonnes of equipment to make about 20 pounds of fuel and probally also if not posistioned right make structuce instability so it will let heat in and may start a fire onboard and blow up like space shuttle columbia but other then that it would be worth it to regain 20 pounds of oxygen*sarcasm*

 

[EtherDragon]

it would only require about 3 tonnes of equipment to make about 20 pounds of fuel and probally also if not posistioned right make structuce instability so it will let heat in and may start a fire onboard and blow up like space shuttle columbia but other then that it would be worth it to regain 20 pounds of oxygen*sarcasm*

I think you guys just made up a bunch of random numbers... unless you can point me to a source.

I recently read an article about the potential of doubling energy density in a Li-ION batery pack (http://www.technologyreview.com/energy/17017/page1/)

And another fun article about the possibility of generating power and using that power to reduce the heat buildup during reentry...
http://www.brighthub.com/science/space/articles/13637.aspx

Besides - with the DG being build from Unobtanium and fueld by DeusExMachanium - who knows what we could model to make DG-style ships feel more "real."

 

[RisingFury]

How do you propose to power a space craft just by batteries?

 

[Andy44]

Oh yes! Let's put insanely heavy machinery and batteries on spacecraft, so we can regain a little bit of energy.

I don't see a reason for being so nasty. The poster put forth an idea. No need for the snark.

 

[Sky Captain]

Skimming the upper atmosphere might be good idea (if technically possible) to replenish the propellant tanks for some sort of nuclear electric rocket allowing to carry much more useful payload since there would be no need to carry propellant for return voyage.

 

[Mindblast]

The problem here is that the gas you're trying to take in is very hot (i think about 8000K when you skim the earth atmosphere at orbital velocity, i'm not even trying to imagine the numbers for Jupiter).. so you would need to confine the stuff magnetically and then find a way of cooling it down and compressing/liquifying it. That would take huge amounts of energy and heavy machinery and also huge radiators for getting rid of the heat.
So nothing you would carry along on a normal spaceship. Maybe a specialised ship for the job but still very unlikely i think.

 

[RisingFury]

I don't see a reason for being so nasty. The poster put forth an idea. No need for the snark.

I didn't mean to be offensive and I apologize for that.


The thing is... everyone has ideas, good and bad. But you gotta be able to be self critical before you post them. Posting some nonsense and then saying "Oh, it's just an idea! Don't be so mad!" is just ridiculous.



I mean... batteries of all things!

Batteries are good to power your RC plane for 5 minutes or to keep your spacecraft operating in Earth's shadow for half an hour or give you the critical functions before the solar panels get deployed... you can't expect batteries to power your space craft for more then an hour or so - at minimum consumption.

Even if you came up with a miracle battery that holds 1000 times more energy per unit of weight and has almost no limits when releasing that energy, that battery would still be no good for spacecraft, because even if you're able to power it for a day... what about the rest of 15 years?

You need a power source that will give you continuous power - like solar panels, RTG or some other power source and a small battery that just acts as a buffer in case the power source goes out for a short period of time.



Also, yes, recapturing gas from atmosphere might sound good, but when you actually think about how this is done, you'll soon figure out it's complete nonsense. Whatever you wanted to install on your spacecraft would give you so much mass penalty that anything you gain from gathering propellant won't make up for it.

 

[Urwumpe]

I mean... batteries of all things!

Batteries are good to power your RC plane for 5 minutes or to keep your spacecraft operating in Earth's shadow for half an hour or give you the critical functions before the solar panels get deployed... you can't expect batteries to power your space craft for more then an hour or so - at minimum consumption.

The Soyuz 7K-T Ferry spacecraft had been powered ONLY by batteries. The early first generation solar arrays had been scrubbed for saving weight so the spacecraft can carry two astronauts with pressure suits instead of three astronauts without.

http://en.wikipedia.org/wiki/Soyuz_7K-T


Maximum endurance was just about three days with batteries, enough for two docking attempts and reentry.

Of course it was not the most capable spacecraft. But it worked very well and was really robust.

The main problem I see is rather that the added complexity for recapturing energy during aerobraking makes no sense, because you can only turn a VERY tiny bit of the energy into electricity. And during reentry you don't need it - a tiny mobile phone size battery is enough for powering a recovery beacon for days to weeks.

You have inlet losses, as you can't create a perfect inlet which does not disturb the airflow - sharper inlet lips mean much higher temperatures and the air speed is not constant around the spacecraft. It can even be subsonic at some places. the ram compression in the inlet would also require complex cooling and inlet geometry control, so you can work over a large range of Mach numbers and Reynolds numbers. Collecting ram air for supplementing the life support system would be pretty complicated as you will also need a heat exchanger and high load check valves.

Then you have turbine losses. You will need to use a reaction turbine, because laminar flow at supersonic flow is hard to get and slowing the air flow down to subsonic is not easy when you are more busy with not melting your spacecraft.

Then you have generator losses, though they are usually not very bad.

You could also use the fact that the plasma is a rapid flow of charges, but then you will need a way to separate electrons and nuclei, so you can induce electricity. Also the efficiency is not very high.

Short: Having a generator there means more trouble than it is worth. It is complete contrary to the design idea of

 

[Mindblast]

You could also use the fact that the plasma is a rapid flow of charges, but then you will need a way to separate electrons and nuclei, so you can induce electricity. Also the efficiency is not very high.

That would be an MHD Generator. AFAIK there is research going on in this field to generate power from the airstream for scram-jet powered hypersonic planes. From what i read the idea is to ionize the air upstream with an electron beam and then have a strong magnetic field with the field lines running parallel to electrodes in the walls of the inlet so the charged particles would be separated by the magnetic field and "captured" by the electrodes.
Also stationary MHD Generators have been used in power plants with efficiencies of about 20% from what i read.. so not too bad.

Though for a spacecraft the bigger problem would be how to store the energy, as RisingFury already pointed out, batteries don't quite cut it.

 

[MAraujo]

Rather than a scoop, why not use the heat differential between say the top and the bottom of the space craft during entry to induce some kind of generator. Maybe a turbine (direct or indirect) could store energy in the form of pressure across an o2 tank bridge.

 

[Usquanigo]

Rather than a scoop, why not use the heat differential between say the top and the bottom of the space craft during entry to induce some kind of generator. Maybe a turbine (direct or indirect) could store energy in the form of pressure across an o2 tank bridge.

[ame="http://www.youtube.com/watch?v=cjjkj-UGboM"]YouTube - Lamina Flow Stirling Engine[/ame]

 

[Mindblast]

That would depend on the amount of energy that can be conducted and radiated away from the upper side to keep it cool. Not sure if it would be enough.

 

[RisingFury]

The Soyuz 7K-T Ferry spacecraft had been powered ONLY by batteries. The early first generation solar arrays had been scrubbed for saving weight so the spacecraft can carry two astronauts with pressure suits instead of three astronauts without.

http://en.wikipedia.org/wiki/Soyuz_7K-T


Maximum endurance was just about three days with batteries, enough for two docking attempts and reentry.

Of course it was not the most capable spacecraft. But it worked very well and was really robust.

Yes, yes, yes... but if you hooked an ion engine on those batteries to give you propulsion, they'd be gone in a few minutes.

Like I said, batteries are good as a buffer and for when you're in a shadow, but there's no way in hell you're gonna be able power your craft purely on batteries. The only reason the early Soyuz used them is because solar cells were just so crappy at the time.



Which brings us to the second part... even if it was possible, why would you wanna recharge your batteries at reentry? It's not like you're gonna be able to convert that power into propulsion. Might as well recharge your batteries once on the ground. It'll probably be way cheaper and easier.


@MAraujo:
You wanna keep the heat out, not let it get in.

 

[Urwumpe]

That would depend on the amount of energy that can be conducted and radiated away from the upper side to keep it cool. Not sure if it would be enough.

Practically not. The luv-side also gets a lot of heating, too much for producing energy that way. Problem is: You need to pump heat from hot side to "cold side", while the crew cabin/payload should be much cooler than even the cold side.

Spacecraft heatshields work by keeping most of the heat away, either by reflection or by ablation.