Could a spacecraft refuel from the atmosphere?

In summary: I'm still confused. You used the word "fuel" in your title and the article is about reaction mass. Which one do you actually mean? By posting the article you imply your idea is similar, but it looks to me like it isn't.In summary, the article discusses a new type of air breathing electric thruster that could be used for long-range space travel. The thruster relies on a continuous high-velocity, low-density atmospheric flux to operate at low thrust values. If the orbit was a high elliptical one, there would be time to rebuild velocity and re-position for each skimming dip into the outer edge of the atmosphere.
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  • #2
Al_ said:
https://phys.org/news/2018-03-world-first-air-breathing-electric-thruster.html

If it dipped into the atmosphere temporarily on an elliptical orbit, could the air gathered be stored for a long flight? Then maybe get more fuel from another planet's atmosphere or moon for the return trip?
Pretty neat article, thanks. But it doesn't seem to match your thread title, or your question about dipping into the atmosphere to "store" O2. The technology in the article appears to rely on a continuous high-velocity, low-density atmospheric flux to operate at low thrust values, no?
 
  • #3
Yes, but the thrust motor, AFAIK, collects the molecules into a chamber as a low density gas as part of the process. At this point, some could be pumped off into a pressure vessel.
The thrust values are low, but if the orbit was a high elliptical one, there would be time to rebuild velocity and re-position for each skimming dip into the outer edge of the atmosphere.
 
  • #4
Al_ said:
to rebuild velocity and re-position
Using what energy source?
 
  • #5
Al_ said:
Yes, but the thrust motor, AFAIK, collects the molecules into a chamber as a low density gas as part of the process. At this point, some could be pumped off into a pressure vessel.
The thrust values are low, but if the orbit was a high elliptical one, there would be time to rebuild velocity and re-position for each skimming dip into the outer edge of the atmosphere.
I'm still confused. You used the word "fuel" in your title and the article is about reaction mass. Which one do you actually mean? By posting the article you imply your idea is similar, but it looks to me like it isn't.
 
  • #6
Well, this idea is actually a basic Bussard Ramjet without fusion (and due the less effective 'gather' part it would rely on an atmosphere).

As long as you can give it enough power to counter the drag, it'll fly. But where would the power come from?
 
  • #7
The original article relies on solar power for the actual energy. If you dip into the atmosphere with solar panels of any significant size, they will fall off, or burn off.

You pretty much end up with a low-power solar-powered space plane (aerodynamically shaped solar "wings") with an ion engine that is only usable around Earth and Venus (no atmosphere on Mercury, not enough sunlight further out unless your wings are enormous) - or you end up with a flying nuke. And not an RTG kind of nuke, but a real nuclear reactor. Because, with current tech:
- a 24 kW (24 thousand Watt) HiPEP produces 460 mN of thrust (half a Newton), ie 1/20th of Earth acceleration for a kilogram of payload.
- An RTG (radio-thermal generator) produces maybe 5 Watt of electricity per kilogram.
- So you need a 4800 kg machine for 1/20th kg of thrust.
(Yes, GOCE used solar, but it had 20 mN of Thrust.)

As for the nuclear option, I guess I will refer you to this thread: http://www.eng-tips.com/viewthread.cfm?qid=104814 . They end up with a 500kg reactor for 1MW power. That enables very high-power electric propulsion that reaches chemical propulsion forces. But you end up with an actual nuclear fission reactor on your ship.
 
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  • #8
Yaro said:
... for 1/20th kg of thrust.
...
Newtons?
The kilogram is not a unit of thrust.
 
  • #9
russ_watters said:
I'm still confused. You used the word "fuel" in your title and the article is about reaction mass. Which one do you actually mean? By posting the article you imply your idea is similar, but it looks to me like it isn't.
Sorry to be vague. I mean reaction mass.
 
  • #10
Yaro said:
If you dip into the atmosphere with solar panels of any significant size, they will fall off, or burn off.
Ah, yes, but if you look at the article, they have dealt with that already. The atmosphere is extremely thin, and the panels are on the sides of the craft. It's essentially orbiting in space, with just a little drag from a very tenuous gas.
 
  • #11
Yaro said:
only usable around Earth and Venus (no atmosphere on Mercury, not enough sunlight further out unless your wings are enormous) - or you end up with a flying nuke.
I wasn't thinking about nuclear. The craft in the article uses solar.
Solar can still work further out - the panels need to be bigger. They could collect power during the high phase of the orbit, it gets stored, then fold up the panels, dip into the atmosphere, run the pump on a little battery power, and go round again. And I think Mercury does have a very thin atmosphere. Maybe it's the right density for this to work?
 
  • #12
Rive said:
Well, this idea is actually a basic Bussard Ramjet without fusion (and due the less effective 'gather' part it would rely on an atmosphere).

As long as you can give it enough power to counter the drag, it'll fly. But where would the power come from?
From photovoltaics, like in the article in the link.
As I understand it the Bussard Ramjet has not yet been built. But this thruster has, although it's not yet flown. I'm just thinking about a next-step innovation.

Perhaps, without the need to carry reaction mass for the return trip, a Mars return mission could be faster? Using Hall thrusters, that is.
 
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1. Can a spacecraft really refuel from the atmosphere?

Yes, it is possible for a spacecraft to refuel from the atmosphere. This process is known as aerobraking or aerocapture, and it involves using the atmosphere of a planet or moon to slow down and change the trajectory of the spacecraft, allowing it to enter into orbit or land on the surface.

2. How does a spacecraft refuel from the atmosphere?

A spacecraft refuels from the atmosphere by using its heat shield to generate drag as it passes through the atmosphere. This drag helps to slow the spacecraft down, and as it loses speed, it can use its engines to control its trajectory and enter into orbit or land on the surface. This process can also be used to save fuel during a mission by using the atmosphere as a braking mechanism.

3. Which spacecraft have successfully refueled from the atmosphere?

Several spacecraft have successfully refueled from the atmosphere, including the Apollo Command Module during its return to Earth, the Space Shuttle during its reentry, and the Mars Reconnaissance Orbiter during its mission to Mars. Future missions, such as the Mars Sample Return mission, also plan to use aerobraking for their spacecraft.

4. Are there any risks or challenges associated with refueling from the atmosphere?

There are some risks and challenges associated with refueling from the atmosphere, such as the potential for the heat shield to fail or the spacecraft to experience unexpected atmospheric conditions. However, these risks can be mitigated through careful planning, testing, and design of the spacecraft and its heat shield.

5. Could refueling from the atmosphere be used for long-term space missions?

Yes, refueling from the atmosphere could be used for long-term space missions. In fact, it is already being considered for future missions to Mars and beyond. By using the atmosphere for braking and fuel-saving, spacecraft could potentially extend their missions and explore more distant destinations in our solar system.

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