161–170 of 522 posts
Since 90% of the cost is probably in R+D of the telescope, one could build and deploy another for another 10%. Why isn't this done? Why is every space telescope completely unique?
Why spend money on JWST 2 when you could as well spend it on ... LUVOIR ? ^^ https://en.wikipedia.org/wiki/Large_Ultraviolet_Optical_Infr...
Earlier quoted context omitted.
Because it's a wrong assumption. Significant cost come from the assembly and testing of all the components itself, that you would have to redo entirely. Also if you were to build just 2 or 3 of them, you can't expect any economy of scale. On top of that, the operational cost of JWST is expected to be around 1B$ for it's lifetime, you could expect that to be similar for every single replica you have. And finally, you…
Assuming your figures are correct, you'll get double the data for another 30% cost. If you wait a month before launching #2, if problems appear in #1 (like the telescope mirror was ground improperly) it can be fixed in #2. The operational cost will not double. The same ground facility, equipment, and staff can manage both. If you're buying two identical launches, you can get a quantity discount. > the benefits of a s…
I think 30% is probably a reasonable guess, based on past programs where people have flown 2. You get to reuse design and some fixturing. You get to share some operational costs. But you're not at unit counts where you benefit from mass production techniques and a whole lot of verification and qualification work are still effectively one-offs for each one.
(You save a whole bunch of costs related to making a repeatable program that can turn out hundreds of an item, but more has to be validated/verified for each unit).
The thing is-- what's the marginal value of the additional data (and of the higher priority data arriving earlier)? Would you rather have 2 James Webbs for $13B, or 1 James Webb & some other $3B mission?
(Or, at the outset/original decision making: do you aim for 2 somewhat simpler telescopes or 1 really awesome telescope with the block of money you're given?)
Since 90% of the cost is probably in R+D of the telescope, one could build and deploy another for another 10%. Why isn't this done? Why is every space telescope completely unique?
The Hubble telescope wasn't unique. It was simply the first one that was pointed away from earth. For the JWST, is there even room for a 2nd telescope at L2?
Earlier quoted context omitted.
Assuming your figures are correct, you'll get double the data for another 30% cost. If you wait a month before launching #2, if problems appear in #1 (like the telescope mirror was ground improperly) it can be fixed in #2. The operational cost will not double. The same ground facility, equipment, and staff can manage both. If you're buying two identical launches, you can get a quantity discount. > the benefits of a s…
I remember having manuals printed in the 1980s. The first manual cost $1000 to print, the second one $1. This was with camera-ready copy. Never mind all the cost of writing the manual, proofing it, and formatting it. When I worked at Boeing, the first forging of a part cost $250,000. The next, just a handful of dollars. At Boeing, the first airplane gets a ton of testing, as the design is being tested. Airplanes #2 a…
Milling 2 parts from billet is cheaper per unit than milling 1 (some shared setup and programming costs), but it's the same amount of raw material and basically the same amount of operator time.
Earlier quoted context omitted.
Assuming your figures are correct, you'll get double the data for another 30% cost. If you wait a month before launching #2, if problems appear in #1 (like the telescope mirror was ground improperly) it can be fixed in #2. The operational cost will not double. The same ground facility, equipment, and staff can manage both. If you're buying two identical launches, you can get a quantity discount. > the benefits of a s…
> Making two adds little cost. I think you are overextending your experience in a production environment here. I’ve worked in both, and the type of builds in these aerospace applications still have huge costs in subsequent runs. Hell, even rebuilding an existing component can be prohibitively expensive. Much of the GSE was likely existing so that’s probably a non-issue.
Often that's because they have to rebuild and reset the tooling. Within the run, though, the incremental cost should be minimal.
The huge costs may be huge, but not huge compared to the cost of the prototype.
Earlier quoted context omitted.
Assuming your figures are correct, you'll get double the data for another 30% cost. If you wait a month before launching #2, if problems appear in #1 (like the telescope mirror was ground improperly) it can be fixed in #2. The operational cost will not double. The same ground facility, equipment, and staff can manage both. If you're buying two identical launches, you can get a quantity discount. > the benefits of a s…
> double the data Yes, but the data has diminishing returns as well. The real value in a second unit is having a backup in the event of a total failure of the first. But that's a hard sell to the taxpayers who fund these things.
I find that hard to believe considering there's literally a universe of things to look at. We find surprising things everywhere we look.
Since 90% of the cost is probably in R+D of the telescope, one could build and deploy another for another 10%. Why isn't this done? Why is every space telescope completely unique?
Since 90% of the cost is probably in R+D of the telescope, one could build and deploy another for another 10%. Why isn't this done? Why is every space telescope completely unique?
Why spend money on JWST 2 when you could as well spend it on ... LUVOIR ? ^^ https://en.wikipedia.org/wiki/Large_Ultraviolet_Optical_Infr...
https://en.wikipedia.org/wiki/Large_Ultraviolet_Optical_Infr...
No mention of ESA again, looks like it is solely NASA project, which it is not. Shame.
What puzzles me is the maneuvering fuel. When that fuel runs out, the telescope can no longer orient itself. This ended the life of the Kepler telescope. But aren't there other ways to orient in space? 1. use pressure from the solar wind 2. have 3 electric motors on 3 axis. Wouldn't spinning those motors rotate the craft? Electric power to do it would come from solar panels, giving it plenty of fuel.
JWST, like many other spacecraft, has reaction wheels to orient itself. The reason Kepler ran out of fuel when it did was that it was expending more maneuvering fuel for attitude control because two of its four reaction wheels failed. Hubble and the ISS also had similar failures. We're getting better all the time at building more reliable components (including reaction wheels and cryocoolers) though. Until a few year…
And to calm down anyone afraid of JWST sharing the same fate - construction of reaction wheels have been changed some time ago to make them significantly more reliable. The source of issues on Hubble, Kepler, FUSE, Hayabusa, Dawn and TIMED was electrical arcing between metal parts of reaction wheels. Static charge was building up like when you rub a ballon against your head. That charge caused arcing that in turn caused metal pitting and increased friction leading to failures. That failure mode was understood only in late 2007, when Kepler was already fully build and ready for launch.
JWSt uses new generation ceramic bearing in its reaction wheels, they have been used in spacecrafts since 2010 with great performance.
