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James Webb is fully deployed

nasa.gov

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Re: James Webb is fully deployed

#181

Post by WalterBright »

sailingparrot wrote: post #102
WalterBright wrote: post #75

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?

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…

I remember a NOVA on one of the Mars landers. Nobody had ever landed anything on Mars with a parachute before, so the developers had a massive problem. They built this humongous facility to test parachutes. One design after another failed, for several months. They finally found a design that worked.

I don't know what building a second chute would cost, but I bet it would be less than one thousandth of the cost of #1.

Re: James Webb is fully deployed

#182

Post by bmitc »

ProAm wrote: post #108
bmitc wrote: post #101

Earlier quoted context omitted.

Can anyone elaborate on these single points of failures? For example, are they actually single points of failure? Or is it a bit of exaggeration for marketing purposes (a bit of under promise, over deliver)?

They are single points of failure.

That's not much of an elaboration. Further, I am doubtful, because something always goes wrong. So if a project that has seen decades of delays and billions of dollars of budget overruns has suddenly invented engineering and processes that yields zero failures, count me surprised.

I just wish there was more elaboration of things they are able to accommodate for as things inevitably pop up and not this hyper focus on a number of supposed single point failures.

Re: James Webb is fully deployed

#184

Post by Beldin »

WalterBright wrote: post #166
lisper wrote: post #133

Earlier quoted context omitted.

> 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.

> Yes, but the data has diminishing returns as well. I find that hard to believe considering there's literally a universe of things to look at. We find surprising things everywhere we look.

$3-5B would go a long way to a new Einstein telescope (ie. gravitational waves detector). It would likey allow for significant sensitivity increases in the existing ones. It could propel the National Ignition Facility or ITER forward. It could be used to build a new Arecibo. It could add an enormous amount of low-frequency telescopes - or other scopes for very large integrated scope arrays.

I'd much rather broaden our view than double it in one narrow band. (Or advance fusion research.)

Re: James Webb is fully deployed

#185

Post by ramesh31 »

WalterBright wrote: post #119
sailingparrot wrote: post #102

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 do have some experience with this. I worked for 3 years on the design of the 757. Thousands of engineers spending maybe 5 years on it.

Just wanted to say that's really awesome. The 757 is by far my favorite Boeing jet of all time. They are so overpowered it feels like taking off in a fighter jet. Delta still flies them from LAX to HNL, and it's always so much better than cramming into a 737.

Re: James Webb is fully deployed

#187

Post by lisper »

WalterBright wrote: post #166
lisper wrote: post #133

Earlier quoted context omitted.

> 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.

> Yes, but the data has diminishing returns as well. I find that hard to believe considering there's literally a universe of things to look at. We find surprising things everywhere we look.

That's not true. The potential for surprises gets smaller and smaller the more data you collect. The Webb will produce surprises at first because it is able to make new kinds of observations that were not possible before, but after a while that new data will be used to improve our models and subsequent observations in the same regime will (almost certainly) be less surprising as a result.

Re: James Webb is fully deployed

#189

Post by ThinkBeat »

WalterBright wrote: post #72

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.

They should have made a port for refueling it.

An internal fuel tank and a high-capacity tank externally

Once the fuel is getting low, launch a refuel. when the new supply gets closed, eject the previous tank, dock the new one.

Easy.

When they managed to du an in air refuel of a SR71 in 1970s . Surely we can dock a fuel tank in 2022?

Re: James Webb is fully deployed

#190

Post by sailingparrot »

godelski wrote: post #172
sailingparrot wrote: post #102

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…

Honestly that doesn't sound like much money. Especially since these projects aren't solely funded by one country, even if one foots most of the bill. Also, $1bn over it's lifetime is really cheap even just for the US alone.

> Honestly that doesn't sound like much money

Well by comparison, here is the cost of two of the most impactful recent-ish (post 2000) space telescopes the US has launched:

- Spitzer: 700M$, JWST being it's successor. This telescope allowed us to detect an exoplanet through light for the first time, refine our understanding of the shape of the milky way, find candidate objects to be further observed by JWST and many more contributions.

- Kepler: 600M$, this is the telescope that allowed us to understand that planets were not rare at all, detecting more than 2500.

So imagine what you can do with 3 to 5B$. Certainly more interesting things than just doubling your data gathering rate of a single telescope.

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