James Webb Space Telescope emerges successfully from final thermal vacuum test • Hacker News Board

Re: James Webb Space Telescope emerges successfully from final thermal vacuum test

#61

Post by boardwaalk » Fri, May 31, 2019, 2:44 PM UTC

rakoo wrote: post #56

Klathmon wrote: post #32

Earlier quoted context omitted.

To be a bit more specific, we can't send something up to fix this because it's magnitudes further away from the earth than Hubble is. JWT will be ~1.5 million km away from earth, in a special orbit around a spot called the "L2 Lagrange point". It's located there so that it can kind of hide in the earth's shadow at pretty much all times and keep all the nearby "bright" things behind the heat shield. For comparison, th…

Minor nitpick, but the L2 point is selected so it doesn't need fuel to stay there. It's like a gravity well of the earth/sun system, any object getting a little further from it will get back to it.

I don't think that's true? At the exact L2 point, the forces are zero, anywhere off that point, they are non-zero, away from the point, from what I understand.

Ref: https://www.space.com/30302-lagrange-points.html "L1, L2 and L3 are all unstable points with precarious equilibrium."

Re: James Webb Space Telescope emerges successfully from final thermal vacuum test

#62

Post by nn3 » Fri, May 31, 2019, 2:45 PM UTC

afpx wrote: post #14

nn3 wrote: post #9

At this price point it better be good. It has to make up for all the other astrophysics missions it killed with its (near) endless budget overruns.

That's a bit cynical. There are many examples of NASA missions that had far exceeded the original expectations.

Let's assume expectations scale with budget.

The original cost estimate was $0.5B [1]. Now it's roughly at $10B. So there was a 20x cost increase.

So if we assume original expectations it would need to exceed original expectations by 20x just to make up for the cost growth.

Of course we also need to consider all the other NASA telescopes that didn't get funded to feed this one. They all would likely have exceeded expectations too. It's hard to estimate those, but at least a factor of two addition seems reasonable. So it has to be 40x better just to not exceed

BTW nothing of this is cynical. It's just basic cost-benefit analysis.

It would have been better to cancel it early and spend a small part of the cost in technology development (and other more manageable telescopes) to make sure such an epic project disaster never happens again.

Re: James Webb Space Telescope emerges successfully from final thermal vacuum test

#63

Post by java-man » Fri, May 31, 2019, 2:46 PM UTC

mhb wrote: post #35

java-man wrote: post #27

what puzzles me all the time is why not build two instead. it looks like the R&D portion of the budget might be greater than the actual manufacturing cost, so building two would be less than 2x the price. if one launch fails, we've got a backup. if both launch, we have two instruments deployed. why don't we do it??

Is there any economy of scale? Why not wait until the first one fails to build another one?

I would expect the R&D costs to dominate.

One does not even need to consider economy of scale. For example, if the R&D is $1 million, and manufacturing one mirror costs $100k, the total price for two mirrors is $1.2 million vs. $1.1 million for one.

Plus, consider a non-zero probability of a launch failure.

Re: James Webb Space Telescope emerges successfully from final thermal vacuum test

#64

Post by jvanderbot » Fri, May 31, 2019, 2:46 PM UTC

NikolaeVarius wrote: post #7

Man, I really want this telescope to succeed its mission, but I just can't get over how complex its deployment procedure is. I am extremely pessimistic about it actually managing to deploy as planned.

I have great faith in it. The "deployables" crowd knows their stuff and all eyes are on them right now.

Re: James Webb Space Telescope emerges successfully from final thermal vacuum test

#65

Post by robertfw » Fri, May 31, 2019, 2:46 PM UTC

rakoo wrote: post #56

Klathmon wrote: post #32

Earlier quoted context omitted.

To be a bit more specific, we can't send something up to fix this because it's magnitudes further away from the earth than Hubble is. JWT will be ~1.5 million km away from earth, in a special orbit around a spot called the "L2 Lagrange point". It's located there so that it can kind of hide in the earth's shadow at pretty much all times and keep all the nearby "bright" things behind the heat shield. For comparison, th…

Minor nitpick, but the L2 point is selected so it doesn't need fuel to stay there. It's like a gravity well of the earth/sun system, any object getting a little further from it will get back to it.

That is incorrect, L2 is not a stable lagrange point, and will require station keeping adjustments to remain in position

Re: James Webb Space Telescope emerges successfully from final thermal vacuum test

#66

Post by AWildC182 » Fri, May 31, 2019, 2:49 PM UTC

Damorian wrote: post #51

skizm wrote: post #34

Anyone know if there are any well paying jobs in space programs of any kind? I've been seeing a growing number of reputable universities offering a wider range of space / aerospace / engineering offerings* and I've been getting curious what's out there. Only issue is, a lot of places I looked pay well below market rates :/ (at least for software engineers). I'll admit my expectations might be off considering I've bee…

Just adding on to this. The government funded research labs and DoD contractors I've had offers from have been seriously sad, which makes me concerned on the quality of their missions, personally. Also it's frustrating because I'd much rather work in that space. I'm a senior dev making ~140k and was just offered 80k in a higher cost of living to manage a team of 10 developers with TS clearance working on spy satellit…

That's really weird... I made more than that as a jr engineer doing imaging satellite flight software. Most of us are over 100k in the Denver area.

Re: James Webb Space Telescope emerges successfully from final thermal vacuum test

#67

Post by TheOtherHobbes » Fri, May 31, 2019, 2:50 PM UTC

NikolaeVarius wrote: post #55

petschge wrote: post #41

Earlier quoted context omitted.

Regarding the 10 missions before Apollo 11: It's a little more complicated. Apollo 1 is the name that was given to honor the astronauts who died in the pad accident. Apollo 2 and 3 didn't exists. But a whole bunch of other tests did exist testing Saturn 5 before we got to the unmanned Apollo 4, 5 and 6 tests. And starting with Apollo 7 humans were included. See https://en.wikipedia.org/wiki/List_of_Apollo_missions fo…

I probably should have known this. I've read alot on Apollo, but never really internalized some of these facts.

The really amazing thing is it took just over a year and a half to get from the first unmanned launch of a Saturn V to the moon landing.

Re: James Webb Space Telescope emerges successfully from final thermal vacuum test

#68

Post by mikepurvis » Fri, May 31, 2019, 2:54 PM UTC

bumby wrote: post #13

d33 wrote: post #8

Earlier quoted context omitted.

Could you elaborate on the complexity, comparing it to other complex science projects that succeeded? I'm a layman, curious if this is actually riskier than what humanity has done so far.

For one, I think it has an astronomically (ha) high number of single-points-of-failure. A quick Google search reported 344.

One imagines that for every single point of failure they've got some kind of plan for how to still derive scientific value while operating it in a degraded state, similar to how Hubble was able to take pictures before service mission 1 and COSTAR.

Re: James Webb Space Telescope emerges successfully from final thermal vacuum test

#69

Post by NikolaeVarius » Fri, May 31, 2019, 2:54 PM UTC

rakoo wrote: post #56

Klathmon wrote: post #32

Earlier quoted context omitted.

To be a bit more specific, we can't send something up to fix this because it's magnitudes further away from the earth than Hubble is. JWT will be ~1.5 million km away from earth, in a special orbit around a spot called the "L2 Lagrange point". It's located there so that it can kind of hide in the earth's shadow at pretty much all times and keep all the nearby "bright" things behind the heat shield. For comparison, th…

Minor nitpick, but the L2 point is selected so it doesn't need fuel to stay there. It's like a gravity well of the earth/sun system, any object getting a little further from it will get back to it.

They need to use fuel to station keep, there is a hard time limit to this.mission

Re: James Webb Space Telescope emerges successfully from final thermal vacuum test

#70

Post by AWildC182 » Fri, May 31, 2019, 2:55 PM UTC

jvanderbot wrote: post #50

skizm wrote: post #34

Anyone know if there are any well paying jobs in space programs of any kind? I've been seeing a growing number of reputable universities offering a wider range of space / aerospace / engineering offerings* and I've been getting curious what's out there. Only issue is, a lot of places I looked pay well below market rates :/ (at least for software engineers). I'll admit my expectations might be off considering I've bee…

I'm betting that in 5-10 years, there will be an explosion of aero startups. But fast and loose don't work as well in space, where everything ends up going 11,000 meters per second at least. The culture will necessarily be a bit more conservative, and as others have mentioned, software is usually a supporting element at best, a necessary evil at worst.

With launch costs falling and hardware getting smaller/lighter it's getting less conservative. It used to be everything was C99, VxWorks and SPARC or worse but a lot of companies are starting to look at newer technologies. Good luck finding one of those projects right now but it is happening.