The Impact of Repairable Satellites
Space is the original throwaway economy. Once a satellite is launched, it is thrown away if it breaks. Its also the reason that one-of-a-kind satellites are so expensive. They can't afford to fail, so no expense is spared to ensure reliability.
In 1973 NASA launched the first repairable and maintainable satellite, Skylab It didn’t change the cost of operating in space. But, it did show a satellite could be repaired. It was an important milestone.
More than 50 years ago, Skylab got off to a bad start.
“At 63 seconds, as the vehicle passed through Mach 1 and was approaching maximum dynamic pressure, the meteoroid shield which covered the cylindrical portion of the workshop was ripped from the main structure. As it separated, solar array number 2 was unlatched and only air pressure kept it from deploying. Solar array number 1 was fouled by debris from the shield which subsequently prevented that array from deploying.” [1]
After orbital insertion, the damage caused Skylab to drift and required constant intervention from the ground to maintain control, with several “near misses” that might have lost the space station. The propellant was used so fast that there might not be enough to keep the station in place.
If not repaired, the heat shield/meteorite shield and solar panel damage was enough to make Skylab unusable. The $2.4 billion ($19 billion in 2023 dollars) spent would have been lost.
Since a crewed Skylab II mission was scheduled to launch 11 days later, there was an opportunity to repair the space station. In those few days, a parasol was built using fishing rods (!) and the repair procedure developed. They also developed a plan to use the Command Service Module to power Skylab until the solar panels were fixed.
With the launch of the Skylab II mission, the crew installed the ad-hoc heat shield, repaired the solar array, and improved control with enough propellant left to keep the space station in orbit for the rest of the planned missions. Subsequent missions improved on the repairs and Skylab. The station was eventually manned for 170 days, well in excess of the planned 140 days.
The lesson learned was that spacecraft, space stations, and satellites can be repaired, even when with a lot of damage. Missions that would have otherwise failed, can be completed successfully. In the 20th century, the only way to do this was with human crews. In the 21st century, the construction and maintenance of large satellites can use robotics to recover from the unexpected. This should improve the success rates with what would otherwise be unrecoverable failures.
When considering space based solar power ( SBSP) satellites, a combination of redundant robotic systems and repeated supply missions can improve their success rate just like manned efforts did at the beginning of the space age.
References
[1] Schneider, W. C., Skylab Lessons Learned as Applicable to a Large Space Station, NASA TM X-73073, April 1976, https://ntrs.nasa.gov/api/citations/19760022256/downloads/19760022256.pdf
Additional Reading
· https://en.wikipedia.org/wiki/Skylab
· https://airandspace.si.edu/stories/editorial/saving-skylab
· https://www.space.com/19607-skylab.html
· Analysis Of Changes In Estimated Cost Of The Skylab Program, The Comptroller General of The United States, June 17, 1971, https://www.gao.gov/assets/b-172192.pdf
· Newkirk , R., Ertel, I., Skylab: A Chronology, NASA SP 4011, 1971, https://www.nasa.gov/wp-content/uploads/2023/04/sp-4011.pdf
· https://www.nasa.gov/history/50-years-ago-second-skylab-crew-begins-record-breaking-mission/
· https://plus.nasa.gov/video/skylab-the-first-40-days-2/
· https://www.nasa.gov/humans-in-space/space-stations/
· https://www.nasa.gov/history/50-years-ago-second-skylab-crew-begins-record-breaking-mission/
· https://www.nasa.gov/history/50-years-ago-the-launch-of-skylab-americas-first-space-station/
· https://www.nasa.gov/history/skylab-2-first-repair-spacewalk/
· https://www.nasa.gov/history/50-years-ago-skylab-2-astronauts-deploy-jammed-solar-array-during-spacewalk-2/
· https://roundupreads.jsc.nasa.gov/roundup/1563
· https://www.nasa.gov/humans-in-space/part-i-the-history-of-skylab/
· https://www.nasa.gov/history/50-years-ago-skylab-2-the-we-fix-anything-crew-2/
· https://www.nasa.gov/gallery/skylab-technical-diagrams/
· https://www.nasa.gov/gallery/skylab/
· https://www.nasa.gov/image-article/russ-arasmith-skylab-artwork/
· https://space.stackexchange.com/questions/53609/how-were-the-skylab-solar-panels-stored-and-deployed
