91–100 of 301 posts
While it‘s awesome to finally see the JWST finally come to close to launch after all those years, now it‘s a close race between it and SpaceX Starship that could have taken the 6.5 meter mirror up to space in one whole piece in its 9m diameter belly rather than having to do all the miraculous origami that took two decades to develop in the first place…
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The JWST will not orbit Earth. It will be located near the second Lagrange point (L2) over 1,500,000 km away (The Moon is just 405,000 km from the Earth). Space Shuttle could not have reached it.
How long can it stay stable at that point? Does it have thrusters to keep a station there? If so, how long is the fuel for them provisioned for? Does use of the thrusters impact the sensors that the telescope uses?
> One kind is called "Secondary Combustion Augmented Thrusters" (SCAT), and they are used for orbit correction (like applied changes in velocity for each maneuver the spacecraft makes and also for orbit station-keeping). The SCATs are bi-propellant thrusters, using hydrazine (N2H4) and dinitrogen tetroxide (N2O4) as fuel and oxidizer, respectively.
> The other kind of thruster on Webb is called a MRE-1, or mono-propellant rocket engine, since it only uses hydrazine. There are eight MRE-1s on Webb, and they are used for attitude control and momentum unloading of the reaction wheels
Ref: https://jwst-docs.stsci.edu/jwst-observatory-hardware/jwst-s...
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I wouldn't trust any payload on a SpaceX ship given their track record.
That's how space travel development works. It doesn't take off; it crashes; it explodes; it fails to land; it works. From then on pretty much, it works.
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Any over budget and poorly run government program I see it as a jobs program. F-35, CalTrain, NASA SLS, etc. This is in stark contrast with partnerships with private industries. For eg DARPA + Moderna or NASA + SpaceX.
All those projects were built by private industry, including the latter two.
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Highly unlikely. That would require designing a new spacecraft from the ground up while also developing new robotics and operations technologies. I'd peg that mission at $300 - $500 million. NASA would almost certainty be better off documenting lessons learned and pursuing a new observatory.
> I'd peg that mission at $300 - $500 million. If that was the cost for that mission, it would be worth it considering JWST cost about 20x that amount.
Earlier quoted context omitted.
The JWST will not orbit Earth. It will be located near the second Lagrange point (L2) over 1,500,000 km away (The Moon is just 405,000 km from the Earth). Space Shuttle could not have reached it.
How long can it stay stable at that point? Does it have thrusters to keep a station there? If so, how long is the fuel for them provisioned for? Does use of the thrusters impact the sensors that the telescope uses?
The point of sitting in a lagrange point is that you can stay there without moving due to two gravitational forces. That's not perfectly accurate, but I don't think it needs constant thrust, just occasional taps.
Earlier quoted context omitted.
The JWST will not orbit Earth. It will be located near the second Lagrange point (L2) over 1,500,000 km away (The Moon is just 405,000 km from the Earth). Space Shuttle could not have reached it.
How long can it stay stable at that point? Does it have thrusters to keep a station there? If so, how long is the fuel for them provisioned for? Does use of the thrusters impact the sensors that the telescope uses?
If the JWST survives launch but has a subsequent mechanical problem that prevents it deploying properly (and it’s the kind of problem that would have been fixable on Hubble, using a shuttle mission) would it be feasible to mount a robotic rescue mission to chase it down and remote-hands it back to life? For less than the cost of just launching another JWST?
And if you bring astronauts close, then I guess that some EVAs in existing suits starts looking appealing vs developing those remote hands.
If the JWST survives launch but has a subsequent mechanical problem that prevents it deploying properly (and it’s the kind of problem that would have been fixable on Hubble, using a shuttle mission) would it be feasible to mount a robotic rescue mission to chase it down and remote-hands it back to life? For less than the cost of just launching another JWST?
The JWST will not orbit Earth. It will be located near the second Lagrange point (L2) over 1,500,000 km away (The Moon is just 405,000 km from the Earth). Space Shuttle could not have reached it.
Earlier quoted context omitted.
The JWST will not orbit Earth. It will be located near the second Lagrange point (L2) over 1,500,000 km away (The Moon is just 405,000 km from the Earth). Space Shuttle could not have reached it.
How long can it stay stable at that point? Does it have thrusters to keep a station there? If so, how long is the fuel for them provisioned for? Does use of the thrusters impact the sensors that the telescope uses?
It does have thrusters - a ring of 16 hydrazine "burning" units that can produce thrust on 3 axis.
The fact that the L2 point is unstable and that thrusters are required puts a lifetime on the telescope - I think NASA plans for a minimum of 5 1/2 years and are hoping to get up to 10. That's entirely reliant on the fuel supply.
The use of thrusters does impact the sensors the telescope uses. NASA et al schedule usable telescope time around burns, and general attitude shifts/correction. The telescope uses a bunch of gyroscopes/flywheels to point itself in the proper direction, during maneuvers like that the sensors aren't operable.