Value chain · CLM-0338
In plain terms
The 1978 design assumed each steering thruster would fail on average once every five years, and that its grids would wear out after about 5,000 hours (roughly seven months) of running. It carried 64 thrusters so that spares could cover failures between yearly maintenance visits.
The claim as recorded
The DOE/NASA 1978 reference design's attitude control system, as described for the 5 GW GaAlAs CR2 option, is sized to 64 argon ion thrusters specifically to provide redundancy against an assumed annual maintenance interval, a 5,000-hour thruster grid lifetime, and a 5-year thruster mean time between failures (MTBF).
Scope and limits
Describes a maintenance-driven redundancy plan for one subsystem (ACS) of one 1978 point design. Does not establish an overall system availability percentage, and does not cover the antenna, power distribution, or other subsystems. The 64-thruster figure is for the GaAlAs CR2 option only; the source states that the silicon CR1 option would need a different number of thrusters and a different propellant load.
What it assumes
These are stated as sizing ASSUMPTIONS for redundancy design, not as demonstrated hardware performance; 1978-era ion thruster technology had not achieved this life in flight at the time of writing.
Where it comes from
PDF p.34 (doc p.22): "A total of 64 thrusters is included in the system to provide the required redundancy assuming: an annual maintenance interval, 5000 hour thruster grid lifetime and a 5-year thruster MTBF."
Basis: hours (thruster grid life), years (thruster MTBF), annual (maintenance interval)
Related records
- Answers question
- QST-002 not published in this release
Cite this
energyaperture.com/c/clm-0338
CLM-0338, Energy Aperture, as of 1978.
Connected records
Other published records linked to this one. A list, not a judgement.
- Also from SRC-085
- CLM-0013The paper that modern UK studies rely on for the beam figure calls anything below 1 kilowatt per square metre safe, with 230 watts per...CLM-0020The original 1978 design set the beam at 230 watts per square metre in the middle of the receiving site, about one twenty-third of that at...CLM-0023In the 1978 reference design, two limits set the size of the transmitter and the receiving site: how much heat the transmitter can shed...CLM-0039The 1978 report set the figure to protect radio and navigation systems from a disturbed ionosphere, called the number theoretical and...CLM-0045The apparent conflict between 12 and 23 was not an error. The underlying study gave a range, and the figure adopted sits near the top of it.CLM-0101The 1978 contract required the researchers to report fixes if ionospheric disturbance pushed the pilot-beam phase error past 2 to 3...CLM-0137In four major space solar power studies from 1978 to 2007, none put a number on how much of the beam's energy would be lost if the beam...CLM-0138The original 1978 government design for beaming power down from space adds up all the expected energy losses to get 63% overall efficiency...More on the source page.