John Mather On the Building of the James Webb Space Telescope 78
Nancy Atkinson writes "Why is the James Webb Space Telescope (scheduled to launch in 2013) taking so long to build? Hasn't it had a huge cost over-run and several delays? Nobel Prize winner John Mather is the Project Scientist for JWST, and he addresses these questions and more in an in-depth interview, one of the few he's given about this next-generation telescope and successor to the Hubble Space Telescope. Quoting: 'The hardest thing to build was the mirror, because we needed something that is way bigger than Hubble. But you can't possibly lift something that big or fit it into a rocket, so you need something that is lighter weight but nonetheless larger, so it has to have the ability to fold up. The mirror is made of light-weight beryllium, and has 18 hexagonal segments. The telescope folds up like a butterfly in its chrysalis and will have to completely undo itself. It's a rather elaborate process that will take many hours. The telescope is huge, at 6.5 meters (21 feet), so it's pretty impressive.'"
Re:Build It in Space (Score:3, Informative)
Re:Not really a successor? (Score:3, Informative)
Re:Will Orion be able to service it? (Score:3, Informative)
thanks, also the previous poster (why is the comment hidden) pointed out the wikipedia article on the JWST but it said amongst other things servicing provisions are still under consideration (2008).
From Wikipedia:
NASA is considering plans to add a grapple feature so future spacecraft might visit the observatory to fix gross deployment problems, such as a stuck solar panel or antenna. However, the telescope itself would not be serviceable, so that astronauts would not be able to do things such as swapping out instruments, as has been done with the Hubble Telescope.[18][19][20][21] Final approval for such an addition will be considered as part of the Preliminary Design Review in March 2008.
That's not a serious effort to make the JWST serviceable.
My big fear is that the launch doesn't go successfully, having a multi-billion dollar spacecraft dependent on a foreign launch vehicle makes me nervous. Maybe that's why they fought over the launch decision to use the (free) Ariane V for two years. I'm very happy Kepler went off okay very unhappy about the Orbiting Carbon Observatory.
You do realize that rockets have different capabilities and reliability? The Ariane V is one of the more reliable rockets out there. So is the Delta II that launched the Kepler mission. If you wanted to launch the JWST, currently, you'd need to use either a Proton (can be launched from Kourou, I think), Ariane V (also from Kourou), or Delta IV Heavy (from Cape Canaveral Air Force Station). I don't think other rockets have the payload capability. If I recall correctly, the Ariane V is actually the most reliable of the group (followed by the Proton, Delta IV Heavy just started so it doesn't have a record) I just mentioned. The OCO was launched on a Taurus which doesn't have a good reliability record (one failure in seven launches).
Re:Build It in Space (Score:3, Informative)
Once we have the ability to build things like this, we can, among other things, build space probes in orbit.
Why would we want to do that?
This simplifies things because they don't have to have the ability to deploy. It also cuts the mass because all of the equipment used to deploy is used exactly once, but is carried for the rest of the mission. It also means that the probe itself doesn't have to be sturdy enough to withstand launch forces, and that the various components can be reinspected and, if needed, have any launch damage corrected before it sets out.
I don't think this is well thought out. You are weighing the cost of building a satellite in space versus Earth-side manufacture with some special deployment. The latter will win in any near future cost evaluation. It doesn't help that a lot of applications can't get rid of the requirements either for nontrivial deployment processes or high thrust trajectories (see the Oberth effect [wikipedia.org]).