Author Topic: Crew Dragon or Orion to Hubble for CMG Replacement?  (Read 11929 times)

Online RonM

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Re: Crew Dragon to Hubble for CMG Replacement?
« Reply #40 on: 10/10/2018 01:44 PM »
Ok, what's so special about hubble that we can't simply build a replacement? Not with all new and super fancy stuff like the want with WFIRST, but with the technology level Hubble has now? Hubble has been launched 30 years ago, upgraded the last time almost 10 years ago.
Why isn't it possible to build something based on a commercial spacecraft bus, for let's say 500 mio. $ that's new and shiny and has the same capabilities of 30-10 year old hardware?
Sure, we'll just manage the program along the lines of the Webb Space Telescope...

The problem with Webb is all the new technology. Building a Hubble replacement with "off the shelf" tech would be reasonable.

Offline Jim

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Re: Crew Dragon to Hubble for CMG Replacement?
« Reply #41 on: 10/10/2018 01:44 PM »

Why isn't it possible to build something based on a commercial spacecraft bus,

Commercial spacecraft buses are not designed for missions like HST.

And still there is the telescope part.
« Last Edit: 10/10/2018 01:45 PM by Jim »

Offline Coastal Ron

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Re: Crew Dragon to Hubble for CMG Replacement?
« Reply #42 on: 10/10/2018 02:00 PM »

Why isn't it possible to build something based on a commercial spacecraft bus,

Commercial spacecraft buses are not designed for missions like HST.

OK, but what would be? And even if they are not designed for such missions, what do they lack for such missions?

Quote
And still there is the telescope part.

In what way?

And not that I think Congress would fund such an effort, but it is an interesting thought experiment given the newer capabilities we have today and in the near future.
If we don't continuously lower the cost to access space, how are we ever going to afford to expand humanity out into space?

Online Lar

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Re: Crew Dragon to Hubble for CMG Replacement?
« Reply #43 on: 10/10/2018 09:46 PM »
(mod) We got a complaint that this discussion isn't SpaceX any more. The irony of that complaint wasn't lost on me... but let's try to stay marginally focused on the topic. A Raptor upper stage, for example, would be off topic.  And stop laughing.

(fan) Also, Rocket parts are not LEGO elements, to be put together in whatever way one can imagine. Doesn't work that way. A D2 mission would take a lot of engineering and be diversionary. When the last HST science (positioning and desaturating) gyro gives out, safe HST and build a fixture to stow it inside a BFS and bring it home. The safe mode gyros should have some considerable life remaining presumably.
« Last Edit: 10/10/2018 10:03 PM by Lar »
"I think it would be great to be born on Earth and to die on Mars. Just hopefully not at the point of impact." -Elon Musk
"We're a little bit like the dog who caught the bus" - Musk after CRS-8 S1 successfully landed on ASDS OCISLY

Offline LouScheffer

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Re: Crew Dragon to Hubble for CMG Replacement?
« Reply #44 on: 10/11/2018 02:50 AM »
No need for a Dragon or crew.  Just a spacecraft bus with rendezvous and docking capability and a separate
non propulsive attitude control system.  The propulsion system used for rendezvous and docking then can be used for reboost.
You left out a tiny little detail: the need to disable Hubble's own attitude control system to allow the ACS of the docked spacecraft bus to take over. Which means completely changing the way the Hubble computers operate the telescope.
Without knowing how it works, I'd guess disabling Hubble's own pointing gyros and actuators and substituting others is not hard. 

To measure its pointing, Hubble needs to measure the state of the gyros, and convert this to angular pointing.   Presumably this is a matrix operation that is in software, since it needs to work with any 3 of the 6 gyros.

Likewise, when Hubble wants to point, it sends commands to the reaction wheels to change speed.  This should also be a matrix operation that projects the desired change in angular state onto the axes of the active reaction wheels.  It is also presumably in software since they need to be able to use any big-enough subset of the wheels.

Assuming the replacement ACS has its own gyros, or its own reaction wheels, or both, then Hubble needs to power down the corresponding internal hardware, then use modified matrix values when reading the new gyros or driving the new reaction wheels.  My main question would be if there is a path with high enough bandwidth from the pointing measurement and computation units in the Hubble to the added module.

Offline speedevil

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Re: Crew Dragon to Hubble for CMG Replacement?
« Reply #45 on: 10/11/2018 09:46 AM »
My main question would be if there is a path with high enough bandwidth from the pointing measurement and computation units in the Hubble to the added module.
As mentioned above, the radios can be used.
Any radio capable of being received at distance can at much lower power (if this is an option) be received by something a few meters away, even if not pointed correctly.
If not capable of reduced power, the transmitter dishes can be pointed into space.

Basically, the payload just pretends to be one of the TDRS network. The only question would be if the latency is low enough.

Offline Mark Lattimer

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Re: Crew Dragon to Hubble for CMG Replacement?
« Reply #46 on: 10/11/2018 12:46 PM »
You merely have to expand Crew Dragon's mission envelope somewhat to include servicing Hubble's cousins, the NRO's KH-11 satellites, and your funding problems are solved.   8)

Offline Jim

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Re: Crew Dragon to Hubble for CMG Replacement?
« Reply #47 on: 10/11/2018 01:19 PM »
You merely have to expand Crew Dragon's mission envelope somewhat to include servicing Hubble's cousins, the NRO's KH-11 satellites, and your funding problems are solved.   8)

That is nonsense

Offline Jim

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Re: Crew Dragon to Hubble for CMG Replacement?
« Reply #48 on: 10/11/2018 01:22 PM »

OK, but what would be? And even if they are not designed for such missions, what do they lack for such missions?



Propellantless attitude control system.  Precise pointing.   Large payload capability. 

Also, most commercial buses are just designed to point at the earth.

Offline vt_hokie

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Re: Crew Dragon to Hubble for CMG Replacement?
« Reply #49 on: 10/11/2018 03:49 PM »
I think it needs to be clarified that there are rate sensing gyros, and momentum/reaction wheels.  What is replaceable on Hubble is the former, but I don't know if the reaction wheels are.  It also uses replaceable magnetic torquers on the arrays for pointing.  Corrections and clarifications welcome of course!

Offline Halidon

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Re: Crew Dragon to Hubble for CMG Replacement?
« Reply #50 on: 10/11/2018 03:50 PM »

OK, but what would be? And even if they are not designed for such missions, what do they lack for such missions?



Propellantless attitude control system.  Precise pointing.   Large payload capability. 

Also, most commercial buses are just designed to point at the earth.
There's a second NRO bird, unless WFIRST is cannibalizing it.

Offline Jim

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Re: Crew Dragon to Hubble for CMG Replacement?
« Reply #51 on: 10/11/2018 04:53 PM »

OK, but what would be? And even if they are not designed for such missions, what do they lack for such missions?



Propellantless attitude control system.  Precise pointing.   Large payload capability. 

Also, most commercial buses are just designed to point at the earth.
There's a second NRO bird, unless WFIRST is cannibalizing it.


They are not spacecraft.  NRO only provided optical assemblies.

Offline tdperk

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Re: Crew Dragon to Hubble for CMG Replacement?
« Reply #52 on: 10/11/2018 05:32 PM »
No need for a Dragon or crew.  Just a spacecraft bus with rendezvous and docking capability and a separate
non propulsive attitude control system.  The propulsion system used for rendezvous and docking then can be used for reboost.


You left out a tiny little detail: the need to disable Hubble's own attitude control system to allow the ACS of the docked spacecraft bus to take over. Which means completely changing the way the Hubble computers operate the telescope.
Update the firmware.

Yes, we need to reconfigure the confabulator.

 :o too soon?

Offline Hog

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Re: Crew Dragon to Hubble for CMG Replacement?
« Reply #53 on: 10/11/2018 10:28 PM »
What about a crew Dragon with 3x crew (2x experienced Shuttle-Hubble Astros) and CMG's in the trunk?! Two of the Astronauts could perform a pair of EVAs to install new gyros and batteries and the other Astro would be there to assist them in suiting up and 'flying' the Dragon.

Can the Dragon be configured to do multiple EVAs? If the Falcon 9 is fully expended and launched to the 28.5 degree inclination orbit that Hubble is in: would the Dragon have enough delta-v to reach the telescope? Can a set of gyros and batteries fit in the Dragon's cargo trunk? I'd love to see someone do a feasibility study on a mission like this!! And could the Dragon dock with the docking unit that was left on the Hubble by the STS-125 crew? Could EVA's be done on the telescope without an RMS system? Or could the crew suffice with the pole system that was being looked at for the now abandoned Asteroid Rendezvous mission?

Or would this be a mission better suited to an Orion, launched on a Delta IV-Heavy, now that the ICPS stage is going to be 'man rated'?

Are there any Astronauts who repaired Hubble still on the active duty roster? How feasible would it be to reinstate 'Hubble Astronauts' who would still pass the physical or have only recently retired? Also: I know that it might be better to plow the mission's money into new space telescopes, or dock a 'stability' CMG control/command module to the base of Hubble...

...I'm only pondering this concept as a 'face saving' idea if - God fervently forbid - if the James Webb ends up in the drink after launch, or fails to deploy.
Bolded emphasis mine.

Types of Astronauts
Former= NASA astronaut that has left NASA or deceased
Active= eligible for flight assignment
Management= employed at NASA but are no longer eligible for flight assignment

Scott Douglas "Scooter" Altman -Former, retired 2010
Gregory Carl "Ray J" Johnson - Former retired 2013
Michael Timothy "Bueno" Good -Management- at JSC serving in the Commercial Crew Program
Katherine Megan McArthur - Active
John Mace Grunsfeld- Former retired 2016
Michael James Massimino- Former retired 2014
Andrew Jay "Drew" Feustel -Active, just returned October 4 2018 from a long duration ISS mission

Of the 7 astronauts that comprised the crew of STS-125, only McArthur and Feustal remain as "Active" astronauts that are eligible for future flight assignment.
Paul

Offline Halidon

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Re: Crew Dragon to Hubble for CMG Replacement?
« Reply #54 on: 10/11/2018 11:20 PM »

OK, but what would be? And even if they are not designed for such missions, what do they lack for such missions?



Propellantless attitude control system.  Precise pointing.   Large payload capability. 

Also, most commercial buses are just designed to point at the earth.
There's a second NRO bird, unless WFIRST is cannibalizing it.


They are not spacecraft.  NRO only provided optical assemblies.
I stand corrected,  didn't know there was no bus included. Thanks for the information.

Online obi-wan

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Re: Crew Dragon to Hubble for CMG Replacement?
« Reply #55 on: 10/12/2018 01:04 PM »
I think it needs to be clarified that there are rate sensing gyros, and momentum/reaction wheels.  What is replaceable on Hubble is the former, but I don't know if the reaction wheels are.  It also uses replaceable magnetic torquers on the arrays for pointing.  Corrections and clarifications welcome of course!
Both the rate sensors and the reaction wheels can be changed out. The RSUs are inside the aft shroud, and one of the hardest tasks for Hubble servicing is getting the access doors open and closed (they tend to flex/jam).

Offline butters

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Re: Crew Dragon to Hubble for CMG Replacement?
« Reply #56 on: 10/13/2018 06:48 AM »
The Chandra x-ray telescope has now entered safe mode and a gyro failure is the preliminary root cause theory. It's like a bad week at the nursing home, the venerable Great Observatories are succumbing to inevitable end-of-life afflictions.

Maybe this should be in a less SpaceXy thread, but I couldn't find one just for the Hubble situation or any thread specifically about Chandra. If I missed the proper location, mods please move.

Offline Hog

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Re: Crew Dragon to Hubble for CMG Replacement?
« Reply #57 on: 10/14/2018 12:35 AM »
The Chandra x-ray telescope has now entered safe mode and a gyro failure is the preliminary root cause theory. It's like a bad week at the nursing home, the venerable Great Observatories are succumbing to inevitable end-of-life afflictions.

Maybe this should be in a less SpaceXy thread, but I couldn't find one just for the Hubble situation or any thread specifically about Chandra. If I missed the proper location, mods please move.
Those great observatories made for some great launch stories. 
 Like when Mr John Shannon, who was STS-93's Asecent/Entry Flight Director over the main flight loop pronounced "Yikes we dont need any more of those." after being informed of the LOX Low Level cutoff off the Space Shuttle Main Engines due the 405 pound Liquid Oxygen shortfall which accounted for the 15 feet per second underspeed.

STS-93 Ascent MCC FCR Internal Loop



https://waynehale.wordpress.com/2014/10/26/sts-93-we-dont-need-any-more-of-those/
Paul

Offline Bob Shaw

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Re: Crew Dragon to Hubble for CMG Replacement?
« Reply #58 on: 10/14/2018 01:06 AM »
You merely have to expand Crew Dragon's mission envelope somewhat to include servicing Hubble's cousins, the NRO's KH-11 satellites, and your funding problems are solved.   8)

That is nonsense

But funny.

Offline Lee Jay

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Re: Crew Dragon to Hubble for CMG Replacement?
« Reply #59 on: 10/14/2018 02:32 AM »
And at this point, I do not have much faith in Webb getting to where it's going and safely deploying with it's nearly insane 'Rube Goldberg' mechanisms and procedures.

Did you see Curiosity's EDL procedure?  To me, that was way harder to execute than the relatively pedestrian JWST deployment.  It was fast, in rough conditions (hot, dusty, etc.) and in an unpredictable environment (rocks, holes, slopes, etc.).

And, as I understand it, Hubble doesn't even have a CMG.  It has rate sensing gyros (which is what is broken), reaction wheels and magnetic torque bars for desaturating the reaction wheels.  Is that correct?

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