Space Shuttle Atlantis is currently in orbit performing the last repair mission to the Hubble Space Telescope. The flight is interesting for a number of reasons. It is the final mission to repair and upgrade one of the most amazing scientific instruments in existence. It also carries a larger amount of risk than most shuttle flights. If NASA discovers any problems with the Space Shuttle Orbiter’s heat shield while in orbit, the crew will not be able to use the International Space Station (ISS) as a safe harbor. Instead, NASA would have to launch a second Orbiter for a risky shuttle rescue mission.
However, for commercial space enthusiasts, the most interesting part of the mission might be the launch of the Soft Capture Mechanism (SCM). The SCM is a rendezvous and docking target for Hubble that will allow spacecraft other than the Shuttle to dock with the telescope.
You see, Hubble was designed around the Space Shuttle. It was launched by the Shuttle, and serviced four times by Shuttle astronauts wielding its robotic arm (this mission is the fifth). And because Hubble is large enough to cause localized destruction on Earth if allowed to reenter the atmosphere in an uncontrolled manner, it was designed to be returned to Earth at the end of its mission in the cargo bay of the Shuttle.
However, when Space Shuttle Columbia burned up on reentry, it became clear that Hubble would not end its life with a funereal ride on the Shuttle to the Smithsonian Museum (as was once considered). Instead, a $1-1.6 billion robotic mission to service Hubble was drafted that would have used a version of the new International Space Station (ISS) arm to service Hubble one last time. When this proved too complex, a simpler version was studied to attach a $170 million propulsion module to Hubble that would deorbit Hubble, sending it to a death of fire and water over (and in) the Pacific Ocean.
Deorbiting Hubble After the Shuttle Retires
To better ascertain what Hubble’s future will look like after the Shuttle retires in 2010 I interviewed Mike Moore, the Program Executive for Hubble. Here’s an excerpt of our email conversation:
Gerend: I understand that there are no official plans to service Hubble past SM4, but are there any ideas of how to deorbit Hubble that you can share with me?
Moore: “We have done several studies on how to de-orbit the observatory, and as you might guess, there are lots of ways to configure a system to do the job. Fortunately for us, it seems that the Solar cycle will allow us to stay in orbit for some time to come, so the need will not be with us until 2020 or so. That means we have the opportunity to take advantage of all the developments that will occur in the coming few years. By that time, there will be several systems that are able to do rendezvous and docking in some fashion, including the European ATV, the Japanese HTV, and our own Orion system. All of these will provide a basis for an automated system that can attach to the observatory and provide the push needed for an accurate re-entry…”
“I have specifically not tried to spec a system that would do the mission now, just because the potential in the future is so great that what we can do now could be so old hat by the time we actually do the job that it might just sound silly.“
Gerend: The LIDS adapter was put there conceivably to allow visitation by Orion, so I assume that this is the baseline deorbit method. Is that correct, or is it simply to provide better options for when deorbit planning begins?
Moore: “You have hit the nail on the head with your latter comment. The Orion, as I mentioned above, is one of many potential “off the shelf” systems that might be made to work in the time frame noted. However, so can many other systems…” “What the adapter does do, we hope, is make the process of docking easier and cheaper.“
So what would the real final Hubble mission look like? Here are some of possibilities:
- A crewed Orion mission The mission could look like this: NASA’s next generation space capsule Orion docks with the telescope, fires its retro rockets to put the pair into a suitable reentry trajectory, and then undocks and adjusts its own trajectory to reenter in the appropriate location.
- An unmanned ATV mission The European Automated Transfer Vehicle (ATV) is currently the most capable spaceship for this task, assuming it could be fitted with a LIDS docking port. It has automated rendezvous and docking capabilities as well as more than adequate propellant reserves. Like the Orion mission profile, it is likely that the ATV would have to disconnect from Hubble before reentering-the combination of both large objects reentering simultaneously would produce a little too spectacular a fireworks (and aquatics) show!
- An unmanned SpaceX Dragon or Orbital Sciences Cygnus vehicle This would be the cheapest option if the private sector can successfully deliver their ISS cargo vehicles, currently under contract with NASA. The mission would have the cargo craft dock with the Hubble’s new LIDS docking port and then place it in an appropriate reentry trajectory or possibly a higher, long-life “museum” or graveyard orbit. However, neither craft (nor the Japanese H-II Transfer Vehicle) is designed for automatic docking. They are designed to be grappled by the ISS robotic arm and manually docked, so these options might not be workable until automatic docking capabilities are developed.
- A crewed SpaceX Dragon mission If the unmanned version of the Dragon or Cygnus cargo vehicles can’t achieve the automated rendezvous and docking task, a small crew could be launched on the crewed version of the Dragon to manually assist with the docking.
As you can see, the final Shuttle flight to the Hubble Space Telescope is a noteworthy mission with an interesting repercussion for the commercial spaceflight industry. The Shuttle isn’t quite the wonder-spaceship it was supposed to be, but it is nonetheless the most capable orbital servicing ship ever created, and when it retires, a significant capability will be lost. However, the inclusion of the new docking port on Hubble means that NASA will have more options when it comes time to service Hubble again or deorbit it, and it’s likely that a commercial option might be the cheapest and best. It also might set the stage for private orbital servicing missions that begin to replace some of the Shuttle’s capabilities.
- Space.com’s coverage of Space Shuttle missions, and the Hubble servicing mission.
- A nice set of pictures showing the preparation of the shuttle for the mission.
- Shuttle rescue mission discussion.
- More information about the Soft Capture Mechanism.
- SpaceX Dragon
- Japanese H-II Transfer Vehicle
- Hubble natural reentry – not likely before 2020.
- Additional information about a robotic service mission to Hubble.
- More information about the Hubble Space Telescope.