How does one “dump” or deplete propellant without changing spacecraft attitude or trajectory?
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Occasionally one reads about a spacecraft "dumping fuel". It may mean expelling the propellant(s) as a liquid, or depleting them by burning them up. Although usually only fuel is mentioned, often the oxidizer is also eliminated at the same time. In any case, the propellants are eliminated from the spacecraft.
How does one do this without affecting the attitude or trajectory of the spacecraft?
Related, but about health/safety of a fuel dump: Any risk from Soyuz 22-ton fuel dump?
fuel trajectory
asked May 27 at 23:44
DrSheldonDrSheldon
16.6k5 gold badges65 silver badges131 bronze badges
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add a comment
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$begingroup$
Occasionally one reads about a spacecraft "dumping fuel". It may mean expelling the propellant(s) as a liquid, or depleting them by burning them up. Although usually only fuel is mentioned, often the oxidizer is also eliminated at the same time. In any case, the propellants are eliminated from the spacecraft.
How does one do this without affecting the attitude or trajectory of the spacecraft?
Related, but about health/safety of a fuel dump: Any risk from Soyuz 22-ton fuel dump?
fuel trajectory
asked May 27 at 23:44
DrSheldonDrSheldon
16.6k5 gold badges65 silver badges131 bronze badges
$endgroup$
2
$begingroup$
related but not the same question (it doesn't address attitude): What is a non-propulsive vent? and, slightly related: What is “propulsive passivation” and why will the SpaceX STP-2 mission do it?
$endgroup$
– uhoh
May 28 at 0:09
4
$begingroup$
If i had to do it, i would eject equal amounts of mass in opposite directions.
$endgroup$
– Paul
May 28 at 4:31
$begingroup$
@Paul: That is basically what RussellBorogove said in his answer below.
$endgroup$
– DrSheldon
May 28 at 5:11
3
$begingroup$
Interestingly, a similar solution is applied to the vacuum cleaner used on ISS.
$endgroup$
– SF.
May 28 at 6:46
add a comment
|
$begingroup$
Occasionally one reads about a spacecraft "dumping fuel". It may mean expelling the propellant(s) as a liquid, or depleting them by burning them up. Although usually only fuel is mentioned, often the oxidizer is also eliminated at the same time. In any case, the propellants are eliminated from the spacecraft.
How does one do this without affecting the attitude or trajectory of the spacecraft?
Related, but about health/safety of a fuel dump: Any risk from Soyuz 22-ton fuel dump?
fuel trajectory
asked May 27 at 23:44
DrSheldonDrSheldon
16.6k5 gold badges65 silver badges131 bronze badges
$endgroup$
Occasionally one reads about a spacecraft "dumping fuel". It may mean expelling the propellant(s) as a liquid, or depleting them by burning them up. Although usually only fuel is mentioned, often the oxidizer is also eliminated at the same time. In any case, the propellants are eliminated from the spacecraft.
How does one do this without affecting the attitude or trajectory of the spacecraft?
Related, but about health/safety of a fuel dump: Any risk from Soyuz 22-ton fuel dump?
fuel trajectory
fuel trajectory
asked May 27 at 23:44
DrSheldonDrSheldon
16.6k5 gold badges65 silver badges131 bronze badges
asked May 27 at 23:44
DrSheldonDrSheldon
16.6k5 gold badges65 silver badges131 bronze badges
asked May 27 at 23:44
DrSheldonDrSheldon
16.6k5 gold badges65 silver badges131 bronze badges
asked May 27 at 23:44
DrSheldonDrSheldon
16.6k5 gold badges65 silver badges131 bronze badges
asked May 27 at 23:44
DrSheldonDrSheldon
16.6k5 gold badges65 silver badges131 bronze badges
16.6k5 gold badges65 silver badges131 bronze badges
2
$begingroup$
related but not the same question (it doesn't address attitude): What is a non-propulsive vent? and, slightly related: What is “propulsive passivation” and why will the SpaceX STP-2 mission do it?
$endgroup$
– uhoh
May 28 at 0:09
4
$begingroup$
If i had to do it, i would eject equal amounts of mass in opposite directions.
$endgroup$
– Paul
May 28 at 4:31
$begingroup$
@Paul: That is basically what RussellBorogove said in his answer below.
$endgroup$
– DrSheldon
May 28 at 5:11
3
$begingroup$
Interestingly, a similar solution is applied to the vacuum cleaner used on ISS.
$endgroup$
– SF.
May 28 at 6:46
add a comment
|
2
$begingroup$
related but not the same question (it doesn't address attitude): What is a non-propulsive vent? and, slightly related: What is “propulsive passivation” and why will the SpaceX STP-2 mission do it?
$endgroup$
– uhoh
May 28 at 0:09
4
$begingroup$
If i had to do it, i would eject equal amounts of mass in opposite directions.
$endgroup$
– Paul
May 28 at 4:31
$begingroup$
@Paul: That is basically what RussellBorogove said in his answer below.
$endgroup$
– DrSheldon
May 28 at 5:11
3
$begingroup$
Interestingly, a similar solution is applied to the vacuum cleaner used on ISS.
$endgroup$
– SF.
May 28 at 6:46
2
2
$begingroup$
related but not the same question (it doesn't address attitude): What is a non-propulsive vent? and, slightly related: What is “propulsive passivation” and why will the SpaceX STP-2 mission do it?
$endgroup$
– uhoh
May 28 at 0:09
$begingroup$
related but not the same question (it doesn't address attitude): What is a non-propulsive vent? and, slightly related: What is “propulsive passivation” and why will the SpaceX STP-2 mission do it?
$endgroup$
– uhoh
May 28 at 0:09
4
4
$begingroup$
If i had to do it, i would eject equal amounts of mass in opposite directions.
$endgroup$
– Paul
May 28 at 4:31
$begingroup$
If i had to do it, i would eject equal amounts of mass in opposite directions.
$endgroup$
– Paul
May 28 at 4:31
$begingroup$
@Paul: That is basically what RussellBorogove said in his answer below.
$endgroup$
– DrSheldon
May 28 at 5:11
$begingroup$
@Paul: That is basically what RussellBorogove said in his answer below.
$endgroup$
– DrSheldon
May 28 at 5:11
3
3
$begingroup$
Interestingly, a similar solution is applied to the vacuum cleaner used on ISS.
$endgroup$
– SF.
May 28 at 6:46
$begingroup$
Interestingly, a similar solution is applied to the vacuum cleaner used on ISS.
$endgroup$
– SF.
May 28 at 6:46
add a comment
|
2 Answers
2
active
oldest
votes
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In many cases, propellant is only dumped when the spacecraft’s mission is complete, so any minor changes to trajectory caused by the dump are unimportant.
If you must avoid any trajectory or attitude change due to a propellant dump, the most straightforward way is to have multiple vents pointing in opposite directions, so the propulsive forces cancel out.
answered May 27 at 23:59
Russell BorogoveRussell Borogove
105k4 gold badges373 silver badges455 bronze badges
$endgroup$
2
$begingroup$
Another approach I've seen done for launch vehicle upper stages (say, for blowdown of the main propulsion system through the engines themselves) is to set the vehicle up in an end-over-end tumble, so that the resulting thrust from the venting cancels out over time.
$endgroup$
– Tristan
May 28 at 13:30
add a comment
|
$begingroup$
It will depend on many factors, but so long as you are NOT using a mono-propellant, then you can simply allow your fuel to run through the system normally (but without lighting it/mixing with oxidiser). This will still result in a slight thrust, but several orders of magnitude less than a 'proper' burn.
If this is done through thruster nozzles, it should be trivial to 'balance' them (even if you are forced to 'light' the fuel, as you would with a hypergolic fuel) so that the net effect is zero.
answered May 28 at 10:26
Mike BrockingtonMike Brockington
4211 silver badge6 bronze badges
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1
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This sounds very plausible theoretically, but do you know any actual engines that allow for this?
$endgroup$
– Hohmannfan♦
May 28 at 21:07
$begingroup$
Good point @Hohmannfan. Since the pumps are typically powered by combustion I'd imagine you couldn't pump the contents out actively. You'd have to just open the valves and let it outgas.
$endgroup$
– Ingolifs
May 28 at 21:51
$begingroup$
@Hohmannfan, the J-2 engine used by the Saturn V third stage. Venting was sufficiently propulsive to turn a lunar free-return trajectory into either a lunar impact or a gravity assist into heliocentric orbit.
$endgroup$
– Mark
May 28 at 22:57
$begingroup$
The shuttle dumped residual LOX through its engines. The LH2 took a different path. There was a significant propulsive effect.
$endgroup$
– Organic Marble
May 30 at 1:55
add a comment
|
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2 Answers
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active
oldest
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2 Answers
2
active
oldest
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$begingroup$
In many cases, propellant is only dumped when the spacecraft’s mission is complete, so any minor changes to trajectory caused by the dump are unimportant.
If you must avoid any trajectory or attitude change due to a propellant dump, the most straightforward way is to have multiple vents pointing in opposite directions, so the propulsive forces cancel out.
answered May 27 at 23:59
Russell BorogoveRussell Borogove
105k4 gold badges373 silver badges455 bronze badges
$endgroup$
2
$begingroup$
Another approach I've seen done for launch vehicle upper stages (say, for blowdown of the main propulsion system through the engines themselves) is to set the vehicle up in an end-over-end tumble, so that the resulting thrust from the venting cancels out over time.
$endgroup$
– Tristan
May 28 at 13:30
add a comment
|
$begingroup$
In many cases, propellant is only dumped when the spacecraft’s mission is complete, so any minor changes to trajectory caused by the dump are unimportant.
If you must avoid any trajectory or attitude change due to a propellant dump, the most straightforward way is to have multiple vents pointing in opposite directions, so the propulsive forces cancel out.
answered May 27 at 23:59
Russell BorogoveRussell Borogove
105k4 gold badges373 silver badges455 bronze badges
$endgroup$
2
$begingroup$
Another approach I've seen done for launch vehicle upper stages (say, for blowdown of the main propulsion system through the engines themselves) is to set the vehicle up in an end-over-end tumble, so that the resulting thrust from the venting cancels out over time.
$endgroup$
– Tristan
May 28 at 13:30
add a comment
|
$begingroup$
In many cases, propellant is only dumped when the spacecraft’s mission is complete, so any minor changes to trajectory caused by the dump are unimportant.
If you must avoid any trajectory or attitude change due to a propellant dump, the most straightforward way is to have multiple vents pointing in opposite directions, so the propulsive forces cancel out.
answered May 27 at 23:59
Russell BorogoveRussell Borogove
105k4 gold badges373 silver badges455 bronze badges
$endgroup$
In many cases, propellant is only dumped when the spacecraft’s mission is complete, so any minor changes to trajectory caused by the dump are unimportant.
If you must avoid any trajectory or attitude change due to a propellant dump, the most straightforward way is to have multiple vents pointing in opposite directions, so the propulsive forces cancel out.
answered May 27 at 23:59
Russell BorogoveRussell Borogove
105k4 gold badges373 silver badges455 bronze badges
edited May 28 at 5:08
answered May 27 at 23:59
Russell BorogoveRussell Borogove
105k4 gold badges373 silver badges455 bronze badges
answered May 27 at 23:59
Russell BorogoveRussell Borogove
105k4 gold badges373 silver badges455 bronze badges
answered May 27 at 23:59
Russell BorogoveRussell Borogove
105k4 gold badges373 silver badges455 bronze badges
105k4 gold badges373 silver badges455 bronze badges
2
$begingroup$
Another approach I've seen done for launch vehicle upper stages (say, for blowdown of the main propulsion system through the engines themselves) is to set the vehicle up in an end-over-end tumble, so that the resulting thrust from the venting cancels out over time.
$endgroup$
– Tristan
May 28 at 13:30
add a comment
|
2
$begingroup$
Another approach I've seen done for launch vehicle upper stages (say, for blowdown of the main propulsion system through the engines themselves) is to set the vehicle up in an end-over-end tumble, so that the resulting thrust from the venting cancels out over time.
$endgroup$
– Tristan
May 28 at 13:30
2
2
$begingroup$
Another approach I've seen done for launch vehicle upper stages (say, for blowdown of the main propulsion system through the engines themselves) is to set the vehicle up in an end-over-end tumble, so that the resulting thrust from the venting cancels out over time.
$endgroup$
– Tristan
May 28 at 13:30
$begingroup$
Another approach I've seen done for launch vehicle upper stages (say, for blowdown of the main propulsion system through the engines themselves) is to set the vehicle up in an end-over-end tumble, so that the resulting thrust from the venting cancels out over time.
$endgroup$
– Tristan
May 28 at 13:30
add a comment
|
$begingroup$
It will depend on many factors, but so long as you are NOT using a mono-propellant, then you can simply allow your fuel to run through the system normally (but without lighting it/mixing with oxidiser). This will still result in a slight thrust, but several orders of magnitude less than a 'proper' burn.
If this is done through thruster nozzles, it should be trivial to 'balance' them (even if you are forced to 'light' the fuel, as you would with a hypergolic fuel) so that the net effect is zero.
answered May 28 at 10:26
Mike BrockingtonMike Brockington
4211 silver badge6 bronze badges
$endgroup$
1
$begingroup$
This sounds very plausible theoretically, but do you know any actual engines that allow for this?
$endgroup$
– Hohmannfan♦
May 28 at 21:07
$begingroup$
Good point @Hohmannfan. Since the pumps are typically powered by combustion I'd imagine you couldn't pump the contents out actively. You'd have to just open the valves and let it outgas.
$endgroup$
– Ingolifs
May 28 at 21:51
$begingroup$
@Hohmannfan, the J-2 engine used by the Saturn V third stage. Venting was sufficiently propulsive to turn a lunar free-return trajectory into either a lunar impact or a gravity assist into heliocentric orbit.
$endgroup$
– Mark
May 28 at 22:57
$begingroup$
The shuttle dumped residual LOX through its engines. The LH2 took a different path. There was a significant propulsive effect.
$endgroup$
– Organic Marble
May 30 at 1:55
add a comment
|
$begingroup$
It will depend on many factors, but so long as you are NOT using a mono-propellant, then you can simply allow your fuel to run through the system normally (but without lighting it/mixing with oxidiser). This will still result in a slight thrust, but several orders of magnitude less than a 'proper' burn.
If this is done through thruster nozzles, it should be trivial to 'balance' them (even if you are forced to 'light' the fuel, as you would with a hypergolic fuel) so that the net effect is zero.
answered May 28 at 10:26
Mike BrockingtonMike Brockington
4211 silver badge6 bronze badges
$endgroup$
1
$begingroup$
This sounds very plausible theoretically, but do you know any actual engines that allow for this?
$endgroup$
– Hohmannfan♦
May 28 at 21:07
$begingroup$
Good point @Hohmannfan. Since the pumps are typically powered by combustion I'd imagine you couldn't pump the contents out actively. You'd have to just open the valves and let it outgas.
$endgroup$
– Ingolifs
May 28 at 21:51
$begingroup$
@Hohmannfan, the J-2 engine used by the Saturn V third stage. Venting was sufficiently propulsive to turn a lunar free-return trajectory into either a lunar impact or a gravity assist into heliocentric orbit.
$endgroup$
– Mark
May 28 at 22:57
$begingroup$
The shuttle dumped residual LOX through its engines. The LH2 took a different path. There was a significant propulsive effect.
$endgroup$
– Organic Marble
May 30 at 1:55
add a comment
|
$begingroup$
It will depend on many factors, but so long as you are NOT using a mono-propellant, then you can simply allow your fuel to run through the system normally (but without lighting it/mixing with oxidiser). This will still result in a slight thrust, but several orders of magnitude less than a 'proper' burn.
If this is done through thruster nozzles, it should be trivial to 'balance' them (even if you are forced to 'light' the fuel, as you would with a hypergolic fuel) so that the net effect is zero.
answered May 28 at 10:26
Mike BrockingtonMike Brockington
4211 silver badge6 bronze badges
$endgroup$
It will depend on many factors, but so long as you are NOT using a mono-propellant, then you can simply allow your fuel to run through the system normally (but without lighting it/mixing with oxidiser). This will still result in a slight thrust, but several orders of magnitude less than a 'proper' burn.
If this is done through thruster nozzles, it should be trivial to 'balance' them (even if you are forced to 'light' the fuel, as you would with a hypergolic fuel) so that the net effect is zero.
answered May 28 at 10:26
Mike BrockingtonMike Brockington
4211 silver badge6 bronze badges
answered May 28 at 10:26
Mike BrockingtonMike Brockington
4211 silver badge6 bronze badges
answered May 28 at 10:26
Mike BrockingtonMike Brockington
4211 silver badge6 bronze badges
answered May 28 at 10:26
Mike BrockingtonMike Brockington
4211 silver badge6 bronze badges
4211 silver badge6 bronze badges
1
$begingroup$
This sounds very plausible theoretically, but do you know any actual engines that allow for this?
$endgroup$
– Hohmannfan♦
May 28 at 21:07
$begingroup$
Good point @Hohmannfan. Since the pumps are typically powered by combustion I'd imagine you couldn't pump the contents out actively. You'd have to just open the valves and let it outgas.
$endgroup$
– Ingolifs
May 28 at 21:51
$begingroup$
@Hohmannfan, the J-2 engine used by the Saturn V third stage. Venting was sufficiently propulsive to turn a lunar free-return trajectory into either a lunar impact or a gravity assist into heliocentric orbit.
$endgroup$
– Mark
May 28 at 22:57
$begingroup$
The shuttle dumped residual LOX through its engines. The LH2 took a different path. There was a significant propulsive effect.
$endgroup$
– Organic Marble
May 30 at 1:55
add a comment
|
1
$begingroup$
This sounds very plausible theoretically, but do you know any actual engines that allow for this?
$endgroup$
– Hohmannfan♦
May 28 at 21:07
$begingroup$
Good point @Hohmannfan. Since the pumps are typically powered by combustion I'd imagine you couldn't pump the contents out actively. You'd have to just open the valves and let it outgas.
$endgroup$
– Ingolifs
May 28 at 21:51
$begingroup$
@Hohmannfan, the J-2 engine used by the Saturn V third stage. Venting was sufficiently propulsive to turn a lunar free-return trajectory into either a lunar impact or a gravity assist into heliocentric orbit.
$endgroup$
– Mark
May 28 at 22:57
$begingroup$
The shuttle dumped residual LOX through its engines. The LH2 took a different path. There was a significant propulsive effect.
$endgroup$
– Organic Marble
May 30 at 1:55
1
1
$begingroup$
This sounds very plausible theoretically, but do you know any actual engines that allow for this?
$endgroup$
– Hohmannfan♦
May 28 at 21:07
$begingroup$
This sounds very plausible theoretically, but do you know any actual engines that allow for this?
$endgroup$
– Hohmannfan♦
May 28 at 21:07
$begingroup$
Good point @Hohmannfan. Since the pumps are typically powered by combustion I'd imagine you couldn't pump the contents out actively. You'd have to just open the valves and let it outgas.
$endgroup$
– Ingolifs
May 28 at 21:51
$begingroup$
Good point @Hohmannfan. Since the pumps are typically powered by combustion I'd imagine you couldn't pump the contents out actively. You'd have to just open the valves and let it outgas.
$endgroup$
– Ingolifs
May 28 at 21:51
$begingroup$
@Hohmannfan, the J-2 engine used by the Saturn V third stage. Venting was sufficiently propulsive to turn a lunar free-return trajectory into either a lunar impact or a gravity assist into heliocentric orbit.
$endgroup$
– Mark
May 28 at 22:57
$begingroup$
@Hohmannfan, the J-2 engine used by the Saturn V third stage. Venting was sufficiently propulsive to turn a lunar free-return trajectory into either a lunar impact or a gravity assist into heliocentric orbit.
$endgroup$
– Mark
May 28 at 22:57
$begingroup$
The shuttle dumped residual LOX through its engines. The LH2 took a different path. There was a significant propulsive effect.
$endgroup$
– Organic Marble
May 30 at 1:55
$begingroup$
The shuttle dumped residual LOX through its engines. The LH2 took a different path. There was a significant propulsive effect.
$endgroup$
– Organic Marble
May 30 at 1:55
add a comment
|
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$begingroup$
related but not the same question (it doesn't address attitude): What is a non-propulsive vent? and, slightly related: What is “propulsive passivation” and why will the SpaceX STP-2 mission do it?
$endgroup$
– uhoh
May 28 at 0:09
4
$begingroup$
If i had to do it, i would eject equal amounts of mass in opposite directions.
$endgroup$
– Paul
May 28 at 4:31
$begingroup$
@Paul: That is basically what RussellBorogove said in his answer below.
$endgroup$
– DrSheldon
May 28 at 5:11
3
$begingroup$
Interestingly, a similar solution is applied to the vacuum cleaner used on ISS.
$endgroup$
– SF.
May 28 at 6:46