Perfect-Scientist-29 t1_j37q5qu wrote on January 6, 2023 at 4:53 PM

Reply to comment by Reddit-runner in NASA And SpaceX Consider Daring Plan To ‘Reboost’ The Hubble Space Telescope by aureliamachiavelli

I have tired to source as much of my data as possible, can you tell me how much you think a JWST replacement will cost, and how you are confident it is less than $2billion dollars with the same or better capabilities? I know since we have proven the massive amounts of new technology successfully, costs will come down, but even Hubble upgrades reusing most of the bus and infra still cost nearly $900 million to upgrade without trying to lift all the mirrors/shields/infra to orbit and assemble only the bare minimum. I just wanted to use the most conservative examples i could find to argue why servicing JWST was still less costly than another $9.7 Billion of space telescope as a ballpark, even if they could make and test in near zero degree vacuum chambers using gold, beryllium plates and near absolute zero actuators, near 0 kelvin acoustic refrigeration half as expensive to manufacture. So given I don't know what SpaceX is going to charge for a JWST servicing mission using a starship, i just wanted to call out the unknowns and that a human rated, rad hardened launch total to service was less clear than what SLS has shown for a journey roughly 1/4-1/5th the L2 distance with a 26-40 ton payload (SpaceX has not stated what the kg/GEO, kg/TLI or kg/Helio will be for starship yet). I am not saying Starship will not make it, and i never commented on wrinkly tanks or raptor production rate (I may have commented that given the replacement rate after test fires that SpaceX needs a new Raptor block to fix the copper oxidation and relight issues, which they did do with Raptor v2). Given that SpaceX is licensing the NASA shuttle patents for the current TPS system and bought the Shuttle tile factory from NASA the Tiles will work. Personally (and its possible i am wrong) i think the Starship tiles will wind up being reworked to prevent zippering/laminar flow issues and the post issue will be resolved with adhesive like the shuttle did when it faced similar issues with early test flights. That aside, we haven't seen Starship leave the atmosphere and re-enter yet with a full test payload even for LEO, so that can effect costs of kg to TLI/L2. As to what sources i am using for Starship capabilities for the next 6-10 years until engines that are much more efficient than raptor come online: Elon said Starship is aiming to get max 100 ton payload to LEO (with optimal apogee in tweets so may be less depending on LEO orbit), social media comments, and the official SpaceX website. https://www.spacex.com/vehicles/starship/

Correct_Inspection25 t1_j3899zu wrote on January 6, 2023 at 6:47 PM

Nitpick here: Didn’t you say the last Hubble refit and boost mission cost a total of $900 million? We are talking large numbers but rounding up another $100 million is a bit unfair as a ballpark estimate for JWST, and argues against your point that refit is a value compared to another brand new telescope with proven current/2023 launch vehicles. Want to also point out that L2 orbital space is finite and without an easy way to gradually deorbit Sats there, is a highly valuable resource. This goes beyond a purely financial argument for refit.

Perfect-Scientist-29 t1_j38e7dj wrote on January 6, 2023 at 7:17 PM

Fair point, will fix. $900M was just what i could find via google, and looks like it was already rounding up all externalities anyway so will edit. Forgot that to the other posters point around how many cheaper systems will start certifying for human rated/heavy lift deep space payloads, this year will see 3-4 L2 capable heavy launch systems debut with Starship, Vulcan, New Glenn and Ariane 6 (Starship and New Glenn have more risk of being bumped to Q1 2024), so that also makes the case for repair/refit even stronger. Will look into how NASA/ESA manage the L2 decommissioning, you have a point that de-orbiting around an L2 frame much further away from a gravity well is more complicated especially if a satellite runs out of fuel to keep the L2 frame orbit stable. Shouldn't there be a parking orbit established like some now used for very extreme orbit (GEO/Helio)? Likely L2 would want to have 1 type of each highly sensitive observatories (Deep infrared (JWST), Hubble replacement for visible light/UV, High energy, and or LIGO/Radar) for data link throughput and cost reasons given the goals for the new Decadal Science survey that initially proposed JWST, and leave the rest of the workload to the much cheaper ground based telescopes using laser correction. https://www.nationalacademies.org/our-work/planetary-science-and-astrobiology-decadal-survey-2023-2032

Reddit-runner t1_j38j4j9 wrote on January 6, 2023 at 7:47 PM

>can you tell me how much you think a JWST replacement will cost, and how you are confident it is less than $2billion dollars with the same or better capabilities?

To be fair, that wasn't a conservative estimate. More like optimistic spitballing.

I based that on the fact that we now already have the tech needed for Webb. A new telescope wouldn't need to be folded due to larger launch vehicles.

And the rule of thumb (as per my aerospace prof) is that if you can double the mass you can cut development and manufacturing cost by a factor of four.

Webb is like 6,500kg. A new telescope could weigh 15 times as much. Obviously the rule of thumb can't be extrapolated linearly by that much. But I'm relatively certain that we could develop and build a similar telescope for $1B if you practically don't have to look at the mass of your components.

>SpaceX has not stated what the kg/GEO, kg/TLI or kg/Helio will be for starship yet

It's 100 tons at minimum to everywhere in the solar system.

Perfect-Scientist-29 t1_j38o69f wrote on January 6, 2023 at 8:18 PM

Can you share which of the space telescope proposals are you talking about? Several of them are 4-8x the mass of JWST, and up to 2-4x times the length of JWST's minimum payload faring even folded up.

Space assembly is going to be required even for a number of the proposals components i mentioned above, or at least multiple heavy lift launches in the star-shield senario.

In engineering space launch systems/vehicles, it isn't just 100 tons everywhere in the solar system, its 100 tons to a specific apogee/orbital altitude/delta V target. That is why Falcon heavy can only get 17.637 tons to Mars (assuming the least fuel consumptive Holman transfer window), but can get 69.4 tons to LEO. https://www.spacex.com/vehicles/falcon-heavy/ This is why Falcon Heavy missed bids on a number of deep space missions as it had to reserve fuel mass to hit the orbital targets and could only hit those numbers in non-re-useable mode (Another reason Ariane 6 was designed to hit SpaceX's disposable price per kg numbers for the Falcon Heavy).

Worth mentioning, re-entry velocity from high LEO/GEO/TLI/L2 is very different compared to re-entry from LEO. Typical low earth orbit re-entry speeds are near 17,500 mph and the Mach number M 24-25 for the lower end of LEO orbits. For Artemis/Apollo/L2 return in days/weeks, it is 24,500 mph (Mach 32). This is another reason why L2/TLI/Helio is a different ballgame when it comes to human rated craft payload and mission price per kg. The asteroid sample return mission this year is i think going to be a record breaker, but coming from another solar orbit entirely would be the high end for re-entry velocity/heat abatement. Stardust sample return re-entry from a deep space location with 28,856 mph (Mach 38, 12.9 km/sec) holds the record for the fastest reentry of any human made object, but would be the upper end of a human based refit mission.

Starship is aiming to get 100 tons of payload (Payload includes mission Life support, deep space shielding, mission/fuel/food/water/air/etc), in 1,000 cubic meters of payload volume to a optimal 98.9° orbital inclination(less optimal inclinations means much less payload to LEO), with an altitude of 310 mi (500km), traveling at a minimum of 11 orbits a day of velocity. Space X has said it will not invest in hypersonic testing facilities, so i want to add that may mean more payload lost as starship will need to move to tiles the same thickness as the space shuttle's as the Hubble servicing missions were at the extreme limit of the LEO orbital band and speed. [It used to be 150 tons but it was reduced as the real performance of the raptors became known, and SpaceX completely scrapped active cooling in exchange for buying the shuttle TPS system from NASA about 2 years ago.] https://upload.wikimedia.org/wikipedia/commons/b/b4/Comparison_satellite_navigation_orbits.svg