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The James Webb Space Telescope has passed the final mission analysis review

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Re: The James Webb Space Telescope has passed the final mission analysis review

#171

Post by dylan604 »

dgrant wrote: post #108
wolverine876 wrote: post #85

Earlier quoted context omitted.

> surely the cost per unit would go down, and launch more than one? Surely? They didn't build a JWST factory. It might go up, as people with specialized skills or knowledge have moved on.

I think the verb tenses were not perfect... I think he just meant: why did they build only 1 in the first place? They could have built N instead, at a lower cost per unit.

Space/Science/Military spending do not seem to follow the normal rules of civilian production nor schedules. Alos, once the satellite is built and launched, there is the ongoing budgeting of the actual operations of the satellite. The budgets are limited in those capacities as well.

Re: The James Webb Space Telescope has passed the final mission analysis review

#172

Post by throwaway2048 »

cnlevy wrote: post #46
detritus wrote: post #18

Earlier quoted context omitted.

I don't know why, but I've had this gut-wrenching feeling for a couple of years now that Something Terrible is going to happen to this before it gets into position at L2. I really hope not, obviously, but this seems like an All Your Eggs In One Basket lesson in the making. We need to commodify this tech, make them somewhat disposable, and sent oodles of them up on Starships.

Using 3 COTS (Commercial Off The Shelf) components with 90% reliability can ensure 99.9% redundancy instead of having a Unique very reliable and even costlier 99.9% custom component can really lower costs. But it can happen only if mass is not a constraint. From Casey Handmer's blog: https://caseyhandmer.wordpress.com/2021/03/04/sls-what-now/ The Perseverance Mars rover cost $2.4 billion, which works out to a few tho…

an important consideration is that SpaceX hasn't in fact, gotten 100 tons of equipment to mars yet.

Re: The James Webb Space Telescope has passed the final mission analysis review

#173

Post by dragonwriter »

abz10 wrote: post #151
bumby wrote: post #140

Earlier quoted context omitted.

> Was the F-35 necessary for threat mitigation. No. Was it framed as the necessary for cost savings, yes. I think we're saying the same thing. The argument is, "Was the F22/F18/Fwhatever/weapon-system necessary for threat mitigation? Yes." With that said, if proponents of the F35 want to frame it as "threat reduction + cost savings" that's how they get the budget approved. But the point stands that without a threat,…

I don’t think it’s a great example of using existential threat for sales, when the whole thing was sold as a cost saving. Pretty much everyone at the time just wanted more F-22s. I was a technical advisor on the project.

> Pretty much everyone at the time just wanted more F-22s

The Navy and Marine Corps didn't, especially after development of the Naval variant of the F-22 was cancelled in 1991.

Re: The James Webb Space Telescope has passed the final mission analysis review

#174

Post by machinehermiter »

detritus wrote: post #18
baggy_trough wrote: post #2

Going to be amazing if this thing can actually unfurl, but I'm scared.

I don't know why, but I've had this gut-wrenching feeling for a couple of years now that Something Terrible is going to happen to this before it gets into position at L2. I really hope not, obviously, but this seems like an All Your Eggs In One Basket lesson in the making. We need to commodify this tech, make them somewhat disposable, and sent oodles of them up on Starships.

I think this part of the problem though. We don't believe we can really do anything at this point so we have turned everything into a stochastic process with multiple draws needed and it gives everyone an out when things don't work.

"Oops, JWST blew up, guess we just got unlucky with that single draw from the urn. Shouldn't have put all our eggs in one basket. "

Just do it. No more urn thinking. Just launch , get in orbit and blow our minds with the data that is sent back. I don't want to hear about anything less than that.

Re: The James Webb Space Telescope has passed the final mission analysis review

#175

Post by jcims »

hypertele-Xii wrote: post #164
jcims wrote: post #75

Earlier quoted context omitted.

Do you know if there is any test footage of that anywhere? That's, to me anyway, the second most amazing thing about the sky crane...that I can't find a single frame of it in operation on earth.

Earth physics are different from Mars physics. What works there wouldn't work here; can't just try it out and see if it works.

Sure the final mission configuration isn't exactly what they would test, but the differences in the sky crane maneuver on Mars and Earth would be relatively easy to factor in (ok, that might be an exaggeration, but its doable). There is a ton of control development that would need to be sorted out so they knew how to integrate it all. For example, I had heard that the primary indicator that the rover had touched down simply watching the throttle on the closed loop flight control system. When it throttled down it meant the rockets were no longer suspending the weight of the rover. If true, I would think you would want to test that quite a bit...

FWIW they tested missile defense 'kill vehicles' on the ground and they will operate at or near orbital velocity in space. The main 'hover thruster' would likely be completely unnecessary in a live exercise:

https://www.youtube.com/watch?v=KBMU6l6GsdM

Re: The James Webb Space Telescope has passed the final mission analysis review

#176

Post by abz10 »

bumby wrote: post #170
abz10 wrote: post #151

Earlier quoted context omitted.

I don’t think it’s a great example of using existential threat for sales, when the whole thing was sold as a cost saving. Pretty much everyone at the time just wanted more F-22s. I was a technical advisor on the project.

> I don’t think it’s a great example of using existential threat for sales, when the whole thing was sold as a cost saving. Again, if there is no threat (perceived or real), there is no need for a weapons system, period. Think of it this way, if there was a proposal for a cost savings for an anti-spacecraft/anti-asteroid system mounted to the JWST? I'm saying no, because there is no credible threat that would prevent…

Threat mitigation is largely nuclear shield; but if you’re taking about maintaining air superiority then the F-22 is where it is at. The Navy carrier fleets and Marines are force projection.

The JSF were sold around cost savings; half the price so you could buy twice as many.

Re: The James Webb Space Telescope has passed the final mission analysis review

#177

Post by prpl »

spaetzleesser wrote: post #139

When I look at project management for the small projects (1-20 people) I am working on I always wonder how projects of such a complexity are managed. It must be freakishly difficult to coordinate all the pieces. The people working on this will also have several stressful months ahead of them. From launch to full deployment so many things can go wrong and there is nothing that can be done when something fails.

Systems Engineering

Re: The James Webb Space Telescope has passed the final mission analysis review

#178

Post by jasonwatkinspdx »

7373737373 wrote: post #160
spaetzleesser wrote: post #139

When I look at project management for the small projects (1-20 people) I am working on I always wonder how projects of such a complexity are managed. It must be freakishly difficult to coordinate all the pieces. The people working on this will also have several stressful months ahead of them. From launch to full deployment so many things can go wrong and there is nothing that can be done when something fails.

I wonder the same for large (especially international) companies, government bureaucracies or other organizations. With thousands of employees and branches in different locations, it must be impossible to get a full understanding of the state of the system.

This is what Systems Engineers do. There's no magic bullet, but the basic process is lots and lots of documents. Much of what NASA does is published openly so you can get a feel for what some of these document types are like. The wiki page gives a decent summary.

Building a model for the system is indeed a big part of the challenge. These days it's increasingly done as a fully detailed software simulation. The big CAD packages have specific functionality for this now. For example SpaceX runs on Siemens NX, and you can wade through their marketing speak to get some idea of how it works. CATIA is also popular with aerospace companies, and Autocad's products with architecture.

Re: The James Webb Space Telescope has passed the final mission analysis review

#179

Post by abz10 »

dragonwriter wrote: post #173
abz10 wrote: post #151

Earlier quoted context omitted.

I don’t think it’s a great example of using existential threat for sales, when the whole thing was sold as a cost saving. Pretty much everyone at the time just wanted more F-22s. I was a technical advisor on the project.

> Pretty much everyone at the time just wanted more F-22s The Navy and Marine Corps didn't, especially after development of the Naval variant of the F-22 was cancelled in 1991.

I’m sure the Navy wished it wasn’t canceled, and the Marines probably would have been happy with Harriers.

The stealth window of usefulness is closing anyway with improved radar.

Re: The James Webb Space Telescope has passed the final mission analysis review

#180

Post by jasonwatkinspdx »

dgrant wrote: post #108
wolverine876 wrote: post #85

Earlier quoted context omitted.

> surely the cost per unit would go down, and launch more than one? Surely? They didn't build a JWST factory. It might go up, as people with specialized skills or knowledge have moved on.

I think the verb tenses were not perfect... I think he just meant: why did they build only 1 in the first place? They could have built N instead, at a lower cost per unit.

Because there's only one L2 point, and it'd be very risky to have two units orbiting. So your spare would just sit around costing money in the case the first one works. The folks that do this are pretty dang good at what they do, so they're willing to bet $10 billion on success the first time, vs $20 billion to hedge with a spare. Even with a spare it's not clear to me a malfunctioning first example would have enough Delta-V to get it safely out of the L2 point proximate.

If it fails, they'll learn all they can, then try again with another follow on project, that likely will take advantage of technological improvements since functional requirements on this one were set in stone. Pre-building a spare just doesn't make sense with this kind of project.

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