17
$\begingroup$

The list of Shuttle missions contains quite a few of in-orbit repairs of commercial satellites.

Meanwhile, Soyuz is about exclusively resupply/crew exchange missions to space stations, and this is the ongoing trend.

Did the era of in-orbit satellite repairs end with the end of the Shuttle program, or did I miss something? Also, are there plans to bring that era back - be it through manned launches, or some robotic missions?

$\endgroup$
16
$\begingroup$

It hasn't ended, it has taken a reprieve. Except for space stations, no docking of any kind is currently occurring (At least, that is publicly admitted), nor has it since the last Hubble Space Telescope servicing mission. But there are a few groups interested in researching this technology. I know that Goddard Space Center has a test setup to do on orbit refueling and battery replacement. I also know that DARPA is interested in the technology. I suspect this will eventually make a resurgence, although it might take a while.

EDIT: Since I wrote this, at least one on orbit servicing mission has happened. Northrop Grumman has docked one spacecraft to another one using the thruster port, allowing the mission to continue for longer than it otherwise would have been able to. It only supplies attitude control, but that is significant for geostationary spacecraft.

| improve this answer | |
$\endgroup$
  • 1
    $\begingroup$ Yes, out of the eyes of the public, the Airforce X-37 could be doing it right now. After all, the space shuttle design was to a large degree supposed to serve military purposes. Launching a new spacecraft as replacement is a hard competitor for a servicing mission to deal with, especialy when considering economic lifetime for military and commercial satellites on the edge of current ability. $\endgroup$ – LocalFluff Jun 27 '16 at 13:12
  • 1
    $\begingroup$ Is the JWST designed to be serviced robotically in some minimal sense? (i.e. some easy attachment-point for an undesigned fixit probe?) $\endgroup$ – Nick T Jun 27 '16 at 20:55
18
$\begingroup$

On-orbit repairs are not being done these days. There are no spacecraft from which repairs can be done on orbit.

Why not?

The Shuttle era showed on-orbit repairs to be very expensive (on the order of the cost of a new satellite), making it not worth bothering for a commercial satellite. After several experiments early on in the Shuttle program, repair missions dwindled until only the Hubble service missions were left.

What would it take to run a repair mission?

There are two major factors you need to make a repair mission possible:

  1. The Shuttle showed that on-orbit repairs become much easier if you can attach the satellite to the spacecraft, and if the spacecraft has a manipulator arm. The arm can be used to move large components around, and it can provide astronauts with a surface to stand on/be attached to.

  2. The satellite also has to be designed for it, with a docking interface, handrails, accessible internals with hatches etc. This makes the satellite more expensive and heavier. The difference was several hundred kg for Hubble.

No current spacecraft contain a manipulator arm or an airlock, so you can't use them. You could bolt the hardware onto an existing spacecraft, but only in an expendable fashion (attached to the service module).

The Space Shuttle had a large cargo bay that contained these items, so it could land with its repair/recovery tools intact.

You'd have to design a new spacecraft that includes these in a way that allows recovery of these expensive parts.

Lowering launch cost changes the economics, and makes it more feasible to design and launch a heavy capsule with spare parts, an airlock and a manipulator arm. At the moment, satellite and launch are in the same cost bracket (\$100-300M each). When launch services become cheaper (say, \$10M) it would become cost-effective to service a satellite rather than replace it.

| improve this answer | |
$\endgroup$
  • $\begingroup$ But Wasn't all this true for the spaceshuttles too? I thought the point of them was recoverying everything except the launching stages. So how one could reduce this? $\endgroup$ – Zaibis Jun 27 '16 at 14:15
  • $\begingroup$ The Shuttle turned out to be much more expensive than hoped for. Spending $500M on a repair when you can build and launch a new satellite makes no sense. $\endgroup$ – Hobbes Jun 27 '16 at 14:19
  • 4
    $\begingroup$ Lowering launch costs may de-incentivize on-orbit repair even futher; instead, it may encourage operators to launch birds with shorter operational lifetimes, allowing them to be upgraded more often. Why repair a sat when you can replace it with a newer/better one for the same cost? Miniaturization trends in sat design also work against on-orbit repair. $\endgroup$ – John Bode Jun 27 '16 at 14:56
  • 2
    $\begingroup$ No. Lowering launch cost doesn't make the satellite itself cheaper, see my answer. $\endgroup$ – Hobbes Jun 27 '16 at 15:01
  • 1
    $\begingroup$ Shorter operation lifetime doesn't make a satellite much cheaper. You save propellant and launch weight, but when launches are cheap that doesn't make much of a cost difference. The only way to save is by making the space-qualified parts less expensive, and those won't be much cheaper when rated for half the lifetime. $\endgroup$ – Hobbes Jun 27 '16 at 19:16

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.