Value chain · CLM-1026
In plain terms
The electric ferry takes half a year to climb to geostationary orbit but burns about an eighth of a kilogram of argon for every kilogram it carries; a chemical stage would burn two kilograms of propellant per kilogram and need almost three hundred trips per satellite. That ratio, not speed, is why the programme chose electric.
The claim as recorded
The reference silicon EOTV is stated at 4,000 t up and 200 t down, 180 days up and 40 down plus 16 days on-orbit turnaround, Isp 8,000 s, 1,156 argon ion thrusters of 120 cm, dry mass 1,462 t, 469 t argon plus 46 t LO2/LH2 per round trip (0.13 kg propellant per kg delivered), 10 round trips per vehicle and $40.7M per flight in 1977 dollars ($10.2 per kg LEO to GEO by division), which Battelle's own low-thrust algorithm reproduces at 170-200 and 40-45 days; the GaAs update in the same NASA volume is 6,814 t in 120 days at Isp 7,963 s on 120 thrusters with 0.864e6 kg of propellant (0.127 kg/kg); and the chemical alternative appears only as a Workshop figure for Boeing's two-stage LO2/LH2 personnel/high-priority cargo OTV, carrying 400 t on 830 t of propellant with 280 flights per satellite, while NASA states that chemical propulsion in general raises the mass to LEO "approximately three-fold".
Evidence behind this: T3-programme summary and JSC data book; model outputs with no flown analogue for the electric vehicle.
Scope and limits
The NASA summary (PDF 10-11 / viii-ix) gives different COTV figures from its section 2 (Si: 160-day round trip, Isp 7,000; GaAs: 3,500 t, 133 days, Isp 13,000, 259 thrusters) and does not say which is current. The 120 cm thruster "exceeds the size of any fully qualified thruster to date" (Workshop III-27), the largest being 30 cm; the trip times are model outputs with no flown analogue. The chemical OTV's 280 flights are a Workshop figure for a Boeing concept, not a costed reference. The "1,156 argon ion thrusters" is not printed in SRC-555 (probe "1,?156" over all 260 pages: none); it is 4 x 289 from p.75 (printed 2-5), "289 thrusters are used at each of the four corners".
What it assumes
The 0.13 and 0.127 kg/kg and the $10.2/kg are division of the stated figures.
Where it comes from
PDF p.72 / 2-2: "The vehicle is sized to deliver 4000 metric tons and return 200 metric tons with an uptrip time of 180 days and down time of 40 days, with a specific impulse of 8000 sec. The total dry mass of the vehicle is 1462 metric tons while the total propellant loading is approximately 500 metric tons." SRC-532 PDF p.129 / B-21, render read: argon 469,000, hydrogen 6,600, oxygen 39,400, payload 4,000,000, start burn 5,977,000 kg; PDF p.131 / B-23: "AVERAGE VEHICLE COST / FLIGHTS PER VEHICLE = 283,600K / 10 = $28,400K ... ARGON 494 TONNES @ $1/kg ... REFURBISHMENT 11,300K ... TOTAL COST PER FLIGHT $40,709K". SRC-532 PDF p.90 / 3-17: "the 180-day flight time quoted by Boeing is reasonable (Battelle's estimate is 170-200 days)". SRC-555 Table 2.2-6 (PDF 83 / 2-13), render read: "PROPELLANT 0.864 ... PAYLOAD 6,814 ... LEO DEPARTURE 8.807" (10^6 kg), "based on a 120 day trip time". Figure 23 (PDF 196 / III-10), render read: "PAYLOAD CAPABILITY = 400,000 KG ... PROPELLANT = 415,000 KG [each stage] ... 280 OTV FLIGHTS PER SATELLITE". SRC-555 PDF p.78 / 2-8: "the mass to low earth orbit requirement is increased approximately three-fold due to chemical propellant requirements". SRC-555 PDF p.77-78 / 2-7 to 2-8, opening section 2.2: "The rationale for electric OTV selection over the conventional chemical systems is clearly illustrated in Figure 2.2-1"; "Since transportation costs from earth-to-LEO is the prime contributor to overall SPS transportation cost, the electric system offers a considerable cost advantage over chemical systems."
Basis: days; tonnes; kg propellant per kg payload; USD 1977 per flight
Related records
- Answers question
- QST-003 not published in this releaseQST-040 not published in this release
Cite this
energyaperture.com/c/clm-1026
CLM-1026, Energy Aperture, as of 1981.
Connected records
Other published records linked to this one. A list, not a judgement.
- Also from SRC-532
- CLM-1024The 1979 government estimate put a heavy-lift flight at about ten million dollars of the day, most of it people refurbishing the vehicle...CLM-1027Getting a crew from low orbit up to the construction site took half a day and a stage the size of a small airliner, refuelled at the top...CLM-1028Building the rockets was priced at seventeen billion 1977 dollars and running them at about 2.8 billion per satellite, or roughly sixty...CLM-1029In 1980 the programme's own accounting had rockets at roughly one dollar in four of a satellite's cost and nearly one in two of the money...CLM-1030The independent 1980 cost review said the government's rocket numbers were fair for the stage the programme was at, then added spare...CLM-1031A launcher a third the size of the reference one would cost about a fifth more per kilogram to fly and need four launches a day instead of...CLM-1033At the higher of NASA's two peak figures, the launches would have needed about 6 per cent of US daily hydrogen output and 30 per cent of...CLM-1034The programme's transportation workshop said the schedule was probably unrealistic, and the programme's cost reviewer said the launcher...
- Also from SRC-555
- CLM-1023The programme's last word on its rockets describes a launcher of about 11,000 tonnes at liftoff flying about once a day, gives fleet sizes...CLM-1025In 1980 the people building the case set themselves a goal of thirty dollars a kilogram to low orbit, hoped for fifteen later, and said in...CLM-1027Getting a crew from low orbit up to the construction site took half a day and a stage the size of a small airliner, refuelled at the top...CLM-1029In 1980 the programme's own accounting had rockets at roughly one dollar in four of a satellite's cost and nearly one in two of the money...CLM-1031A launcher a third the size of the reference one would cost about a fifth more per kilogram to fly and need four launches a day instead of...CLM-1033At the higher of NASA's two peak figures, the launches would have needed about 6 per cent of US daily hydrogen output and 30 per cent of...CLM-1034The programme's transportation workshop said the schedule was probably unrealistic, and the programme's cost reviewer said the launcher...