3 ms·
Super exiting. * JWST costs ~$10B, about the same as Large Hadron Collider or aircraft carrier. * JWST has 344 single-point-of-failures (SPOF), 80% of them re
by nabla9 5y ago
Super exiting.
* JWST costs ~$10B, about the same as Large Hadron Collider or aircraft carrier.
* JWST has 344 single-point-of-failures (SPOF), 80% of them related to deployment.
* No ability for repair. JWST goes to orbit the Sun 1.5 million kilometers away from the Earth, almost 4 times the distance between Earth and Moon.
* Ariane 5 launch failure rate is 0.045
---
assuming 0.045 launch failure probability, and 0.0001 failure probability for each SPOF, the mission failure probability is ~8%.
0.955×(1−0.0001)^344
- guerrilla 5y ago> 0.0001 failure probability for each SPOF Why did you choose this value for the assumption? Is that standard or a publicized detail?
- nabla9 5y agoI picked relatively high number 1/10000 as a starting point to get a ballpark. NASA has never tested deployment in the zero gravity. It's unlikely that the probability is higher. Ariane launch failure probability dominates if you add zeros. 0.00001 -> 4.8% 0.000001 -> 4.5%
- wiz21c 5y agoThis makes a 92% success rate... I'm not sure I would cross a road if I had that much chance to be hit by a car :-)
- efitz 5y agoI’m much more concerned about what will happen once the telescope is in operation. We can’t send astronauts to L2 to fix it like we could send them to Hubble on STS.
- pfdietz 5y agoWe can't yet, but doing so isn't entirely out of the question. It's easier than sending anyone to Mars. The one-way trip time for astronauts to L2 might be 25 days. https://www.wired.com/2012/04/100-day-mission-to-sun-earth-l2-1999/ https://www.wired.com/2012/04/100-day-mission-to-sun-earth-l...
- api 5y agoJWST apparently does have some kind of docking attachment so we can service it if we get the capability between now and EOL. Servicing once could likely double its useful life. Starship and Orion could do it AFAIK. Maybe Dragon with a service module.
- mlindner 5y agoThe docking attachment was originally planned but there's been no mention of it in the last 10 years or so and no pictures of such an attachment point. They probably de-scoped it.
- redisman 5y agoI’m guessing they can’t service it by adding more fuel? That would’ve been a neat expansion to be able to expand its life
- dredmorbius 5y agoThe possibility has been engineered, though the mission profile does not rely on this. JWST does have a docking ring: https://www.space.com/3833-nasa-adds-docking-capability-space-observatory.html https://www.space.com/3833-nasa-adds-docking-capability-spac... Deets on station-keeping http://www.ai-solutions.com/Portals/0/AI%20Docs/Technical%20Paper%20Library%20pdf/2014/ISSFD24_Petersen_et_al_JWST_MCC_Monte_Carlo.pdf http://www.ai-solutions.com/Portals/0/AI%20Docs/Technical%20... (PDF) NASA's official FAQ deems servicing does "not offset the increases in mission complexity, mass and cost that would be required to make Webb serviceable, or to conduct the servicing mission itself." https://jwst.nasa.gov/content/about/faqs/faq.html#serviceable https://jwst.nasa.gov/content/about/faqs/faq.html#serviceabl...