Why Solar Power Satellites Can Be Launched Quickly
The first systems in space were single satellites that did everything in one launch. Sputnik in 1957 was the first example of this kind of system [1]. But one launch is not enough to create large space stations and fast communication networks.
Skylab in 1973 was the first US space station. [2] It was orbited with a single launch and for a long time was the most massive object in orbit at 90.6 tons. The first space station to exceed this mass was the Mir. [3] It first launched in 1986 and took 10 years to assemble in orbit. When completed, it massed 129.7 tons, an incremental increase over Skylab. Mir was followed by the International Space Stations (ISS) which was first launched in 1998. It has been under continuous construction since then with a mass of about 450 tons. [4] The Taingong Space Station is the latest space station to be assembled in orbit with 68.7 tons of mass in orbit so far. [5]
In addition to single structures like space stations, there are distributed systems like constellations. The first large constellation was Iridium that first launched in 1997. When completed 95 satellites and a combined mass of 65.4 tons were launched. [6] This constellation was refreshed as Iridium starting in 2017 with 80 satellites totaling 68.8 tons in orbit. [7]
Starlink is in an entirely different class of system. It currently has more than 5800 satellited launched with a total mass exceeding 2,150 tons. [8]
An interesting metric to look at the is the effective mass per year placed in orbit for these systems. For most of the past 50 years, the pace of launch and assembly/integration was about 30 tons per year. With Starlink, SpaceXis successfully deploying more than 500 tons a year into a working system. This is more than an order of magnitude faster then on any prior space systems.
This pace is accelerating. The last 10 Starlink launches deployed satellites at a pace of more than 1250 tons/year.
One of the long standing objections to space based solar power (SBSP) was the launch pace required to economically launch and assemble a system in orbit. [9][10] A slow launch pace drives up the cost of power on the ground due to financing and the cost of ongoing operations. Estimates went as high as 10 years to launch and assemble a satellite. With more than 100 launch providers operating today and demonstrated launch and system integration rates in excess of 1250 tons a years, this is no longer a limitation.
References
References
[1] https://en.wikipedia.org/wiki/Sputnik_1
[2] https://en.wikipedia.org/wiki/Skylab
[3] https://en.wikipedia.org/wiki/Mir
[4] https://en.wikipedia.org/wiki/International_Space_Station
[5] https://en.wikipedia.org/wiki/Tiangong_space_station
[6] https://en.wikipedia.org/wiki/Iridium_satellite_constellation
[7] https://space.skyrocket.de/doc_sdat/iridium-next.htm
[8] https://en.wikipedia.org/wiki/Starlink
[9] https://nss.org/wp-content/uploads/2017/07/1981-NRC-Electric-Power-From-Orbit-1-Report.pdf
[10] https://www.nasa.gov/organizations/otps/space-based-solar-power-report/
[11] https://www.researchgate.net/publication/377865839_Survey_of_Space_Based_Solar_Power_SBSP
Images
- Iridium image - By Cliff - originally posted to Flickr as Iridium Satellite, CC BY 2.0, https://commons.wikimedia.org/w/index.php?curid=6439519
- Iridium Next image - https://space.skyrocket.de/doc_sdat/iridium-next.htm
- Taingong Space Station - By Shujianyang - Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=124945822
Additional Reading
- https://en.wikipedia.org/wiki/Assembly_of_the_International_Space_Station
- https://en.wikipedia.org/wiki/List_of_Starlink_and_Starshield_launches
