<p>Probably, but not for a long time.</p>
<p>JWST is fueled with hydrazine thrusters (similar to <a href="https://en.wikipedia.org/wiki/Reaction_control_system" rel="nofollow noreferrer">RCS</a>) and of course, it only has so much fuel. This isn't Spaceflight Simulator; we can't have infinite fuel (please excuse my gaming humor). While the probability that JWST will run out of fuel is high, the chances it happens before they run out of <a href="https://jwst.nasa.gov/content/about/innovations/cryocooler.html" rel="nofollow noreferrer">coolant</a> is very low. The thrusters will likely not be an issue at all. Another factor on Webb's side is that the <a href="https://en.wikipedia.org/wiki/Ariane_5" rel="nofollow noreferrer">Ariane 5</a> is a very, very good and accurate rocket, like a European version of Atlas V (makes me think that 5 must be the lucky number of rockets, Ariane 5, Atlas 5, Saturn 5) and so, the injection burns were really precise.</p>
<p>As astrosnapper also mentioned, the End-of-Life maneuver (Or as I call it, the space coffin) will require fuel. For example, geostationary satellites are usually moved into a very high graveyard orbit at the end of their mission. I can see something similar with JWST, except for the fact that JWST is about as high as it gets already.</p>
<p>Basically, when you put this all together, no, thruster fuel likely will not be an issue.</p>

CC BY-SA 4.0
2023-02-26T12:11:24.220Z
The JWST RCS thrusters are not gas thrusters. They use hydrazine as a monopropellant. Hydrazine is also used in conjunction with an oxidizer (dinitrogen tetroxide) to power the larger thrusters used for orbit maintenance.
David Hammen
CC BY-SA 4.0
2023-02-24T20:41:38.450Z
2023-02-27T16:22:06.583Z
2023-02-27T16:22:06.583Z
Deko Revinio
<p>JWST will eventually run out of propellant but the injection accuracy of the Ariane launch vehicle was sufficiently high that there is considerably more fuel and oxidiser reserves available than originally budgeted for, such that other sources of failure may well limit the lifetime of the observatory instead.</p>
<p>In the <a href="https://www.stsci.edu/files/live/sites/www/files/home/jwst/science-planning/user-committees/jwst-users-committee/_documents/jstuc-0822-observatory-status-menzel.pdf" rel="nofollow noreferrer">JWST operations report</a> (slide 16) to the <a href="https://www.stsci.edu/contents/events/jwst/2022/august/the-13th-meeting-of-the-jwst-users-committee-jstuc?filterUUID=b192a413-817a-42cf-9f69-70e03d52c4f9" rel="nofollow noreferrer">13th Meeting of the JWST Users Committee</a> in 2022 August, the propellant life is discussed in some detail and based on the estimates of fuel (hydrazine) and oxidizer needed for station-keeping, momentum unload and contingencies, the lifetime for fuel and oxidizer are 26.9 and 35.3 years respectively. There is also fuel reserved for the End of Life maneuver as JWST will need to be disposed of and parked in a secure orbit at the end of the mission as was done previously for e.g. <a href="https://www.esa.int/Enabling_Support/Operations/Herschel_ends_operations_as_orbiting_testbed" rel="nofollow noreferrer">Herschel</a>. The end of life maneuver may get carried out before the propellant runs out if there are concerns that something else might fail and there wouldn't be proper command and control of the spacecraft to carry out the end of life maneuver. This means that there would be no plans to operate without thrusters or gyros in the same way as the <em>Kepler</em> spacecraft was operated for additional time as the K2 mission using the pressure of sunlight to balance the spacecraft and compensate for the failed gryos.</p>

CC BY-SA 4.0
2023-02-24T20:27:59.437Z
2023-02-24T22:05:52.343Z
2023-02-24T22:05:52.343Z
astrosnapper
<p>As far as I know the only mechanism that our spacecrafts have to maneuver in space is gas thrusters.</p>
<p>Obviously pressurized gas is in a limited quantity on the JWST. What are the plans for when the time comes and there's no more thrust power to rotate the telescope ?</p>
<p>Are there any other methods to provide a force on the craft to make it turn or change course ? (maybe some kind of internal mechanical rotational vibration ?)</p>

CC BY-SA 4.0
2023-02-25T12:42:00.670Z
For what it's worth, the JWST doesn't use thrusters to rotate and point the telescope. It uses [reaction wheels](https://en.wikipedia.org/wiki/Spacecraft_bus_(James_Webb_Space_Telescope)#:~:text=JWST%20has%20six%20reaction%20wheels,unregulated%20pressurant%20for%20all%20propellants.). Thrusters don't provide anywhere near enough fine control to keep a space telescope pointed at its chosen targets; thrusters are for station keeping, and bleeding angular momentum from the reaction wheels when they become saturated.
notovny
CC BY-SA 4.0
2023-02-25T23:52:42.010Z
different but related Q&A [How much fuel did JWST save due to an accurate launch, and how much will remain after L2 orbit?](https://space.stackexchange.com/q/57648/12102) and sort-of [To what extent could JWST continue to be useful after the propellant runs out?](https://space.stackexchange.com/q/56082/12102)
uhoh
CC BY-SA 4.0
2023-02-28T00:16:26.387Z
@notovny You should add an answer since the reaction wheels used for pointing are different than the other answers about maneuvering, and correct a misconception in the original post that only thrusters exist.
JohnHoltz
<james-webb-space-telescope>
Is the James Webb Space Telescope ever going to run out of thruster power to point it to the right direction?
Demis
# Is the James Webb Space Telescope ever going to run out of thruster power to point it to the right direction?

(Asked by: username_0 on 2023-02-24)

As far as I know the only mechanism that our spacecrafts have to maneuver in space is gas thrusters.

Obviously pressurized gas is in a limited quantity on the JWST. What are the plans for when the time comes and there's no more thrust power to rotate the telescope ?

Are there any other methods to provide a force on the craft to make it turn or change course ? (maybe some kind of internal mechanical rotational vibration ?)

**Tags:** james-webb-space-telescope

> **Comments:**
> **username_1**: For what it's worth, the JWST doesn't use thrusters to rotate and point the telescope. It uses [reaction wheels](https://en.wikipedia.org/wiki/Spacecraft_bus_(James_Webb_Space_Telescope)#:~:text=JWST%20has%20six%20reaction%20wheels,unregulated%20pressurant%20for%20all%20propellants.). Thrusters don't provide anywhere near enough fine control to keep a space telescope pointed at its chosen targets; thrusters are for station keeping, and bleeding angular momentum from the reaction wheels when they become saturated.  
> **username_2**: different but related Q&A [How much fuel did JWST save due to an accurate launch, and how much will remain after L2 orbit?](https://space.stackexchange.com/q/57648/12102) and sort-of [To what extent could JWST continue to be useful after the propellant runs out?](https://space.stackexchange.com/q/56082/12102)  
> **username_3**: @username_1 You should add an answer since the reaction wheels used for pointing are different than the other answers about maneuvering, and correct a misconception in the original post that only thrusters exist.  

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## 2 answers

### Answer by username_6 on 2023-02-24. Score: 4 | Accepted answer

JWST will eventually run out of propellant but the injection accuracy of the Ariane launch vehicle was sufficiently high that there is considerably more fuel and oxidiser reserves available than originally budgeted for, such that other sources of failure may well limit the lifetime of the observatory instead.

In the [JWST operations report](https://www.stsci.edu/files/live/sites/www/files/home/jwst/science-planning/user-committees/jwst-users-committee/_documents/jstuc-0822-observatory-status-menzel.pdf) (slide 16) to the [13th Meeting of the JWST Users Committee](https://www.stsci.edu/contents/events/jwst/2022/august/the-13th-meeting-of-the-jwst-users-committee-jstuc?filterUUID=b192a413-817a-42cf-9f69-70e03d52c4f9) in 2022 August, the propellant life is discussed in some detail and based on the estimates of fuel (hydrazine) and oxidizer needed for station-keeping, momentum unload and contingencies, the lifetime for fuel and oxidizer are 26.9 and 35.3 years respectively. There is also fuel reserved for the End of Life maneuver as JWST will need to be disposed of and parked in a secure orbit at the end of the mission as was done previously for e.g. [Herschel](https://www.esa.int/Enabling_Support/Operations/Herschel_ends_operations_as_orbiting_testbed). The end of life maneuver may get carried out before the propellant runs out if there are concerns that something else might fail and there wouldn't be proper command and control of the spacecraft to carry out the end of life maneuver. This means that there would be no plans to operate without thrusters or gyros in the same way as the *Kepler* spacecraft was operated for additional time as the K2 mission using the pressure of sunlight to balance the spacecraft and compensate for the failed gryos.


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### Answer by username_4 on 2023-02-24. Score: 1

Probably, but not for a long time.

JWST is fueled with hydrazine thrusters (similar to [RCS](https://en.wikipedia.org/wiki/Reaction_control_system)) and of course, it only has so much fuel. This isn't Spaceflight Simulator; we can't have infinite fuel (please excuse my gaming humor). While the probability that JWST will run out of fuel is high, the chances it happens before they run out of [coolant](https://jwst.nasa.gov/content/about/innovations/cryocooler.html) is very low. The thrusters will likely not be an issue at all. Another factor on Webb's side is that the [Ariane 5](https://en.wikipedia.org/wiki/Ariane_5) is a very, very good and accurate rocket, like a European version of Atlas V (makes me think that 5 must be the lucky number of rockets, Ariane 5, Atlas 5, Saturn 5) and so, the injection burns were really precise.

As username_6 also mentioned, the End-of-Life maneuver (Or as I call it, the space coffin) will require fuel. For example, geostationary satellites are usually moved into a very high graveyard orbit at the end of their mission. I can see something similar with JWST, except for the fact that JWST is about as high as it gets already.

Basically, when you put this all together, no, thruster fuel likely will not be an issue.

> **Comments:**
> **username_5**: The JWST RCS thrusters are not gas thrusters. They use hydrazine as a monopropellant. Hydrazine is also used in conjunction with an oxidizer (dinitrogen tetroxide) to power the larger thrusters used for orbit maintenance.  

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