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  #1  
Old 09-30-2022, 12:33 AM
Bob Austin Bob Austin is offline
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Default NASA Looking to SpaceX to Service Hubble Space Telescope

NASA has announced that it will be conducting a feasibility study on using the SpaceX Dragon to service the Hubble Space Telescope and boost it into a higher orbit.

Hubble is currently orbiting about 540 kilometers above the earth. This is about 60 kilometers lower than its initial orbit. At the current rate of decay Hubble has about a 50% chance of reentering the earths atmosphere by 2037.
Complete article over at Space.com
https://www.space.com/nasa-spacex-possible-dragon-mission-hubble-space-telescope
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  #2  
Old 09-30-2022, 06:33 AM
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This would be fantastic if it ever materializes. Hubble has done so much. I'd like to see it put into a very long term orbit so that when at some point in the future and its useful life is over, and it becomes feasible to capture it and return it to Earth at a reasonable cost, NASA does so and places it in the Smithsonian. It deserves to be there.
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Old 09-30-2022, 12:46 PM
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Reboost, or de-orbit Hubble, yeah.

"Service", whole lotta problems trying to do that with the shuttle gone. Dragon-II ain't shuttle.

Unfortunately, by the time that a reboost might be needed, Hubble will likely have too many critical parts stop working, rendering it useless. Like, say, the last gyro on one of the three axes (IIRC there are two gyros per axis). Torque Gyros wear out a lot.

Effectively, cancelling the shuttle was also dooming Hubble from any future service mission to fix any hardware problems.
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Old 09-30-2022, 02:23 PM
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Too bad they didn't specifically design it for robotic servicing.

Hubble Robotic Servicing and De-orbit Mission: Risk Reduction and Mitigation (unfortunately behind a paywall)
18 September 2007


(Abstract) The Hubble Space Telescope (HST) Development Office spent over a year developing the Hubble Robotic Servicing and De-orbit Mission (HRSDM) with the objectives to autonomously rendezvous with and capture HST, perform robotic servicing tasks (gyroscope and battery changeout and installation of scientific instruments), and ultimately de-orbit the observatory after its useful scientific mission lifetime. During this time, the HST Development Office established the feasibility of performing Earth-based telerobotic servicing of a NASA asset in Low Earth Orbit and advanced the technology readiness level of the following component technologies and techniques: autonomous rendezvous and capture (ARC Object Recognition and Pose Estimation algorithms that successfully measured the relative position and orientation of a robotic interface fixture to an accuracy of ± 2mm in position and ± 2.0 degrees in orientation (with respect to the camera frame of reference) at a distance of 45 cm from the camera; and the development of a space flight qualified 1K x 1K monochrome digital video camera system that is going to be used as part of a Relative Navigation Sensor experiment during the next shuttle-based servicing mission to HST.

Lots of concept images:

Hubble Robotic Servicing and Deorbit Mission (HRSDM)

https://www.edcheung.com/job/hrsdm/hrsdm.htm

The loss of the Space Shuttle Columbia in February 2003 caused a reexamination of the capabilities of the Space Shuttle. As a result of this, the decision was made in January 2004 to not service HST any longer with a human crew, but to allow it to decay gradually out of a operational state. After much behind-the-scenes work, in October of 2004, NASA changed directions slightly, and we formed a team consisting of MDRobotics, Lockheed Martin and the Hubble Project to build a robotic vehicle to service the Hubble Space Telescope.

Space tug

https://en.wikipedia.org/wiki/Space_tug
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Old 09-30-2022, 02:47 PM
Bob Austin Bob Austin is offline
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Jessica Jensen, vice president of customer operations and integration at SpaceX, said, "We're going to be looking at Dragon capabilities and how they would need to be modified in order to safely rendezvous and dock with Hubble. Details of exactly physically how that's done, and how we also safely do that from a trajectory point of view — that's all to be worked out."
...
And a Dragon Hubble mission, should it come to pass, wouldn't necessarily need to be crewed, she added. The feasibility study might point planners toward an uncrewed mission, with Dragon or perhaps even a different type of vehicle.

No SpaceX mission to Hubble is currently in the works. The new announcement concerns a feasibility study, which is expected to last six months and involves no NASA money. (The agency is participating via an unfunded Space Act Agreement.)


https://www.space.com/nasa-spacex-p...space-telescope
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Old 10-09-2022, 10:58 PM
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The main problem with using Dragon to reboost anything, including the Hubble or ISS, is that its main Draco thrusters point FORWARDS on either side of the docking tunnel, under the nose cap (the four large nozzles flush to the surface of the spacecraft). It has multiple maneuvering thrusters located around the outside of the vehicle for translation maneuvers (IOW, steering and pointing the spacecraft, speeding it up slightly or slowing it down or backing it up, etc) but these are low-thrust engines.

Starliner was designed for its service module on back to contain the propulsion system... this puts its four big retrorocket motors on back, so it does an "eyeballs in" retrofire for reentry, flying backwards like all previous capsule designs. Dragon is different-- it uses its four big thrusters on the FRONT of Dragon in an "eyeballs out", forward facing flying retrofire braking maneuver to reentry... after it performs retrofire, it reorients itself flying backwards, closes the nose cap, and jettisons the trunk. The Dragon "trunk" isn't really a service module-- Dragon doesn't particularly need one, not in the "traditional sense". All of Dragon's propulsion systems are in the CAPSULE, so they are all brought back and REUSED. The trunk is just a hollow structure to connect the Dragon to the second stage, and provide room on its surface for solar cells/panels, aerodynamic fins to help with stabilizing the spacecraft in an abort, and unpressurized cargo space inside its hollow structure.

For Dragon to be able to reboost, a "thruster package" kit would have to be engineered to fit inside the trunk, and load paths and suitable controls set up to operate it and integrate it into the spacecraft control system. Putting a 'rocket pack" into the trunk, firing AFT, would do the job that the FORWARD FACING Draco thrusters could not, because their engine plumes would impinge on whatever spacecraft they were docked to. The other option might be long thruster firings of the maneuvering thrusters on the outside of Dragon, but I doubt that would be very effective or efficient.

Seems to me that would be the easiest way to modify the Dragon spacecraft to be able to be used for "reboost". This could help ISS as well, since reboost was something that the troubled Starliner spacecraft was supposed to be able to do, IF it ever actually flies to ISS and is an operational spacecraft. With such a propulsion kit added to the trunk, Dragon SHOULD be able to do reboost just as Starliner would.

For a manned servicing mission, EVA suits would be required. Technically the SpaceX suits are "IVA" suits, made only for depressurized use INSIDE a spacecraft to protect the astronauts from an emergency depressurization of the cabin. While carrying some regular EVA suits along shouldn't be a problem, the gear can be carried as cargo, of course it all has to be checked out to work together nicely without unforeseen problems. Not sure if Dragon is meant to be pressurized/depressurized to conduct EVA's, BUT that's not a huge issue. A Dragon COULD rendezvous and dock with a pre-positioned "work module", which could be little more than a pressurized can with a docking adapter on one end for Dragon to mate with, and whatever is necessary to lock onto and grab Hubble (or any other satellite for that matter) on the other end, and a side hatch for EVA's. Once docked to the Dragon, the module would work virtually identically to how the docking adapter worked on the Apollo Soyuz Test Project back in 1975... that was a one-off construction, carried into orbit atop the same Saturn IB that injected the ASTP Apollo into orbit, which then turned around, docked to it (as it would a lunar module on a Moon flight) and then extracted it from the top of the S-IVB stage. (It might be possible to do something similar with a Falcon 9/Dragon launch, with special fairings between the Dragon Trunk and the top of the Second Stage to house the adapter, or it could be launched on a separate unmanned Falcon 9 using standard fairings as a payload like any other satellite, remaining in orbit to be docked with by the manned Dragon when it arrives in orbit).

The docking adapter in this case, instead of connecting two pressurized spacecraft from different countries and allowing their crews to pass from one to the other, instead it would serve as an "airlock chamber" between the pressurized Dragon and the vacuum of space. It would be equipped with oxygen/gas cylinders to contain enough gases to repressurize and vent the airlock the required number of times to complete the mission, with a hatch to seal it off from Dragon (or using Dragon's forward hatch for this purpose) and once depressurized, allow astronaut(s) to exit the adapter's side hatch to work on Hubble (or whatever). Then when the spacewalk was completed, reenter the side hatch, close it, and repressurize the adapter, then open the hatch to Dragon to allow them to reenter the spacecraft. The docking adapter COULD be fitted, if needed or desired, with a robotic arm for grappling or capturing the Hubble if needed, or for use on other missions. If the adapter were designed right, it could be left in orbit and designed for reuse, with "plug and play" connections for being resupplied with gases and such from a pallet launched as cargo up to it, etc. Once any repairs were conducted on Hubble (or whatever), the propulsion package installed in the trunk could then boost the Hubble (or whatever) through the adapter module it's docked to, through the Dragon and trunk attached to it, into a higher (or appropriate as desired) orbit. Once in the proper orbit, the module could then detach from Hubble, or remain attached, and then maneuver away, and the adapter module could be either left in a parking orbit nearby, or for safety in a lower parking orbit for possible use in the future by another Dragon servicing mission, or simply disposed by putting it into a reentry intersection orbit and cast off.

Dragon could then perform retrofire in the normal manner, cast off the trunk and its propulsion package mounted inside to burn up, and reenter normally.

All it takes is some engineering work, and money... Later! OL J R
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Old 10-10-2022, 10:01 AM
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It would probably be simpler, faster, and cheaper for SpaceX to design a purpose built vehicle specifically for reboosting and orbital maintenance instead of adding a package to the trunk. It's something that's already been done, but on a smaller scale than the HST.

If they actually do decide to service the HST, then a manned mission would be a whole different ball game. I don't think they can do it 100% roboticly. A robot couldn't have closed the bay doors on the HST service mission and likely couldn't now if that portion of the HST had to be accessed again.
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Old 10-10-2022, 04:55 PM
Bob Austin Bob Austin is offline
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Scott Manley has a pretty good video on how SpaceX and Dragon may be used to both service and boost Hubble. It can be found at https://youtu.be/RXarNOCMV3c
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Old 10-11-2022, 06:17 AM
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How much servicing does NASA expect the James Webb telescope to require? Hopefully the big impact it endured was just a fluke.

Dragon/Falcon 9 as currently configured cannot get out there and back. And it will not be able to carry much in the way of tools or spare parts.

Maybe the Starship if it finally becomes operational? Nothing currently envisioned for NASA would be able.

Edit: Starliner maybe?


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Old 11-16-2022, 01:32 PM
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Quote:
Originally Posted by Bill
How much servicing does NASA expect the James Webb telescope to require? Hopefully the big impact it endured was just a fluke.

Dragon/Falcon 9 as currently configured cannot get out there and back. And it will not be able to carry much in the way of tools or spare parts.

Maybe the Starship if it finally becomes operational? Nothing currently envisioned for NASA would be able.

Edit: Starliner maybe?


Bill


JWST has NO service missions planned... why everything had to work PERFECTLY the first time-- one and done.

That said, there's technically no reason a service mission COULDN'T be done if there was the desire and money to do it. Orion technically could be flown out there-- it's a million miles to ESL-2 where JWST is in a halo orbit. That's 4X the distance to the Moon, but technically less challenging in terms of propulsion-- once you're through escape velocity, you're 3/4 of the way to anywhere. It would actually take less propellant to send Orion to JWST than the current Artemis 1 mission, because it would take less propellant to brake into ESL-2 halo orbit alongside JWST than to get into low lunar orbit, which Artemis 1 is incapable of (not enough fuel/propulsion capability, which is why it's going into a highly elliptical lunar orbit with a perilune of about 80 miles and apolune of about 75,000 miles IIRC). Of course an airlock and tool/equipment servicing pallet (cargo pod) would be highly beneficial and would be extra mass that has to be taken along, increasing propulsion requirements/budgets.

There's technically no reason a Crew Dragon couldn't do such a mission, either. People scream that the Crew Dragon isn't meant for deep space, but the differences aren't as huge as people think-- and spacecraft are modified all the time. Again the main thing is propulsion, and navigation. Crew Dragon is intended for up to six months in space, not sure how long Orion is rated for. With either it's not a "run around the block" and using minimal propulsion would take about a month to get out there and a month back, BUT if you have extra propulsion capability (larger service module or stage along for the ride) you could get there MUCH faster, BUT the propellant required to BRAKE into ESL-2 halo orbit is also much greater. Nothing really impossible about it.

Launching off a Falcon Heavy would give you a lot of serious load carrying capability for extra propulsion/service module/stage and/or a airlock/servicing pallet. Either carried up at the same time, or a dual-launch scenario... depending on how you designed the mission, I could see either a pair of Falcon Heavies, a Falcon Heavy and a Falcon 9, or perhaps even a pair of Falcon 9's capable of launching the mission. Maybe a single launch of Falcon Heavy if the mission masses and propulsion budget worked out right.

Now, what they'd be capable of doing when they GOT THERE, that's a separate issue. JWST was designed specifically to fly alone in a "one and done" mission mode. It carries sufficient propellant for the projected lifetime (which thanks to the Ariane V launch vehicle accuracy, actually saved a good deal of propellant on the spacecraft). The JWST has to do a minor burn periodically to stay in the halo orbit of ESL-2, as it's not a "stable orbit" per se, and requires periodic tweaking to not just drift off into space. It also has to stay stable and keep the heat shield permanently pointed toward the Sun and Earth, so that the mirrors and instruments NEVER receive any sunlight-- that's why the heat shield is SO important-- to keep the instruments in the perpetual darkness and thus cold of deep space, so the infrared instruments STAY cold, using only as little supplemental coolant as possible... which is finite and will eventually run out, at some point beyond the projected lifetime of the infrared telescope. Once the coolant is gone, the instruments will gradually warm up somewhat, thus "blinding" them to the far infrared parts of the spectrum. Thus a servicing mission would have to account for all these factors... working on the mirror/instrument side of the telescope would have to be done in total darkness with only minimal work lights (infrared heat sources) since they'd warm up the instruments and mirrors. Even the radiating body heat of an astronaut in a suit would throw a considerable heat load onto the mirrors and instruments-- they would literally glow like a hot coal in infrared, giving off heat that would be absorbed into the instruments and mirrors via radiative heating. SO work times would be limited and require careful scheduling. Whether the instruments would even be capable of being accessed, who knows-- they weren't designed to be. How much good any astronaut could do "fixing a mirror" would be questionable as well-- those things are INCREDIBLY finely polished and coated and precision ground/aligned, and a human mucking about with it would be the last thing the scientists or designers would want IMHO. For those reasons, I think any servicing of the instrument or mirror "dark" side of the spacecraft would be out of the question.

Of course perhaps they could refuel it, but then again, sufficient fuel was saved in the transit and halo orbit insertion maneuvers to give JWST a long-extended lifetime. So what else would there really be to do? Working on the sun-side of the sun shield would protect the instruments and mirrors from stray heat or other issues created by a spacecraft or astronauts, but there's really little that would potentially need servicing from that side... Radios, thrusters, and propellant is about it... maybe the sunshield, but again it's designed to take a given amount of damage without compromising the mission, and whether any sun shield damage would be reparable by human astronauts is questionable.

I think that the scientists and engineers looked at the cost/benefit ratio of the Hubble servicing missions and figured there was no reason to bother designing JWST for servicing. After all it's 4X the distance to the Moon out away from the Sun and Earth in ESL-2 halo orbit-- it would require a deep space independent dedicated mission to even attempt servicing it, which would be expensive and risky. No free return trajectory from ESL-2, for instance. Plus, Hubble's servicing missions have basically exceeded the cost for a new telescope, at least using the Shuttle. We could have literally launched a brand new version of HST by expendable rocket for the cost of each HST servicing mission. Ultimately that would have been FAR better in terms of science return, because 1) the existing telescope(s) would have continued to operate for some time, while the new one was running as well, giving additional observation time and results until the unserviced one finally died, and 2) Hubble was trapped in the worst possible orbit for a space telescope, that is, Low Earth Orbit. 45 minutes out of every 90 minutes, there's a huge honkin' planet in the way of whatever it's looking at in deep space (Earth) AND because it's constantly passing into and out of Earth's shadow every 45 minutes, twice in each 90 minute orbit, the thing heats up and cools down to the +250 degree sunlight to the minus 250 in Earth's shadow, which causes vibration-inducing "popping" of the structure as it expands and contracts, leaving several minutes of each pass useless for observations due to vibrations in the telescope from the thermal-induced popping. BUT that was the ONLY orbit that the shuttle could achieve to launch and service Hubble, in fact the Hubble missions were the highest shuttle flights ever flown, because they taxed the shuttle's capabilities to their limits. It would have actually been FAR BETTER to launch Hubble on an expendable rocket and put it FAR from Earth, where the Earth would be only a "small marble" or tiny dot in its field of view, giving virtually unlimited observation time, and where it would have been FAR from Earth's shadow and in perpetual sunlight, thus eliminating the popping issue and the subsequent disruptions of observations. OF course a shuttle could NEVER have reached it for servicing, however... only a deep-space capable capsule/spacecraft could have gotten to it out in deep space beyond LEO (either in probably geosynchronous orbit, or beyond it at EML-1 or EML-2, where they're proposing putting the Gateway station, if there IS a Gateway station). EML 3, 4, or 5 would be great positions for space telescopes, at the same distance as the Moon but either directly opposite the Moon in its orbit, or 30 degrees ahead or behind the Moon in its orbit). Even Orion in its current form would be capable of servicing a space telescope at those locations, and Dragon could be modified to do so.

Eventually we need a NEW space telescope, something far larger and grander than the aging Hubble. I'd like to see a 10 meter or larger space telescope launched... whatever the largest telescope that could be fit into either SLS or Starship when it flies... something that would make Hubble look like a backyard refractor scope in its capabilities. Something put out into a TRUE observational-optimized orbit, at one of the Lagrange points of the Earth-Moon system, which could be serviced by deep-space capable spacecraft, and not hobbled by the pathetic limitations of the obsolete Shuttle system.

Later! OL J R
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