131–140 of 188 posts
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Newton's birthday sounds like the perfect day for a rocket launch to me
He was born January 4th, using modern calendars. https://www.britannica.com/biography/Isaac-Newton
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I suspect the deployed structure cannot handle the acceleration required for escape velocity. That also may require much more propellant. Then on top of that, we don’t have the capability for humans to service satellites other than the ISS. So this is all a moot point.
We had the capability in 1993, and could of course develop it again. A broken JWT could wait a few years in orbit.
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They calculated that. Building a second JWST would have added 10% to the budget, but the budget committee nixed that. YOLO (you only launch once).
The JWST only has a planned mission duration of 10 years. If it’s as epic as everyone claims it could be, there must be a follow up mission planned. So even if it fails, we’ll still see a successor at some point.
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What booster would you use? Another booster up in the fairing? That would need to be quite heavy. It would be a totally custom thing for this specific mission. You would need a suitable storable propellant. Leave the booster from the Ariane attached? The lh2 and lox would boil off after a few days. What do you do if the deployment fails? SpaceX's dragon can't do space-walks on its own, it doesn't have an airlock. The…
For space walk accessibility maybe they should have docked it to the ISS for initial setup before then boosting it to its final point?
We're told that since JWT will travel very far away before it unfolds and activates all its systems, there is no practical way to service it if something would go wrong. Why can't it unfold etc in Earth orbit, where a repair mission can be sent if needed, and then travel to its Lagrange point?
To get from low-earth orbit to the sun-earth Lagrange point 2 (where the JWT is headed) takes around 7 km/s of delta-v[0]. That's a lot of speed.
You could try to do this gently enough that the unfurled JWT won't be damaged by the acceleration. This isn't totally impossible, but you'd need a good Hall thruster (ion engine) with a huge amount of reaction mass, since the JWT is so big itself. It would need to run for longer than any other such thruster has. It would need massive solar panels to power it.[1]
Or you could have the original rocket just be bigger, and throw it all the way to the right orbit while everything is packed tight.
[0] https://en.wikipedia.org/wiki/Delta-v_budget [1] I'm guessing at this, but that's my intuition. I encourage anyone to correct me because space is too cool to be upset that I was wrong.
We're told that since JWT will travel very far away before it unfolds and activates all its systems, there is no practical way to service it if something would go wrong. Why can't it unfold etc in Earth orbit, where a repair mission can be sent if needed, and then travel to its Lagrange point?
We probably wouldn’t have a way to service it in earth orbit either. We needed a space shuttle to operate on Hubble. And using some other commenter’s estimate a 2nd JWST would cost 10% of the 10 billion USD price of the first one. A billion dollars is ballpark what it costed to launch a space shuttle. So even if we had the shuttle, would we fix the first one or just build & launch a second one?
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That may be true, but designing a mission based off that hypothetical is a bad idea. The reality is we currently don’t have the capability for humans to service satellites, and developing that capability would probably take years and cost >$100 million. And NASA can’t just decide to take on that endeavor, it would require congress and months of political bickering. JWST was designed for what is currently feasible and…
$100M is 1% of what JWST cost. Looks like a reasonable repair cost (and only if) it turns out to be broken.
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Interesting though. Does that really matter without air resistance? Depending on how high you actually bring it. Like 500km away from earth is still an orbit (I think that's Hubble's orbit) but how much force do you need or will happen?
The parts of a ship that thrusters are directly attached to experience acceleration first, the other parts that are further out from the thrusters won't accelerate immediately and if the acceleration is too sudden or extreme could be damaged or break off entirely. And to answer your question in the other response, many thrusters have a minimum thrust, and even that minimum may be too much for the parts when deployed.
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That may be true, but designing a mission based off that hypothetical is a bad idea. The reality is we currently don’t have the capability for humans to service satellites, and developing that capability would probably take years and cost >$100 million. And NASA can’t just decide to take on that endeavor, it would require congress and months of political bickering. JWST was designed for what is currently feasible and…
> developing that capability would probably take years and cost >$100 million. And NASA can’t just decide to take on that endeavor So what you're saying is, this could easily be funded by some billionaire, e.g. Jeff Bezos who already sells billions of dollars in Amazon stock per year to fund Blue Origin? Not saying this should be done privately, but if funding is the problem, that problem can be solved. Space travel…
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> Unlike say, the Apollo program, which had a guaranteed successful outcome? Apollo was wildly dangerous. Apollo 1 killed the whole crew. The contemporary calculated failure odds for a Saturn V launch were 1/8. Compare that to the current Dragon 2 projected LOC risk of 1/276 [1]. [1] https://en.wikipedia.org/wiki/Crew_Dragon_Demo-2#:~:text=NAS... .
I think GP was being sarcastic.