VC10 Launch and orbital transport
Depth of coverage
At its target depth of L3. What the depth levels mean.
What this layer covers
Launch price per kg, cadence, fairing and mass constraints, orbit choice and transfer, launch availability
Where it ends
In scope as a cost and cadence parameter; out of scope as a launch-vehicle technology assessment
Deep area
This layer is studied in more depth than most. It belongs to the deep area In-orbit assembly and mass.
Launch and orbital transport
Launch dominates cost in NASA's model, and no launch contract at the scale and rate these systems need has been signed at any of the prices quoted (CLM-0382). In that NASA model of two designs, launch is 71% and 77% of lifecycle cost. Of every 13 launches, 12 only carry fuel for payloads bound for geostationary orbit, the high orbit where a satellite stays over one point on Earth (CLM-0144). NASA's sensitivity run reports 62% total cost savings for its electric-propulsion variant, in which electric tugs move payloads between orbits instead of refuelling. This site's own calculation, built from NASA inputs, finds that the levelised cost, the lifetime cost per unit of electricity, falls 67%, to 0.2069 USD/kWh, after a 17.2% mass penalty for electric propulsion. That is still four to ten times the cost of the ground-based comparator (CLM-0601). The company Virtus Solis estimates USD 665/kg to low Earth orbit for a Starship that is not reused (CLM-0532). A January 1980 workshop of NASA, contractor and university staff judged the programme's timing unrealistic for space transport (CLM-1025).
Scope. This section covers the price of lifting mass into orbit, how many launches a design needs, and how the parts reach their working orbit. It treats launch as an input of cost and launch rate. It does not assess rocket technology. In NASA's model, a satellite of thousands of tonnes needs thousands of flights, most of them only to carry fuel (CLM-0144). So launch price and the route from low Earth orbit (LEO) to geostationary orbit (GEO, the high orbit where a satellite stays over one point on Earth) drive much of the cost. Total cost is covered in What it would cost.
What is settled. Launch is the largest cost in a NASA model of two designs, at 71 per cent of lifecycle cost for one and 77 per cent for the other (CLM-0144). The model assumes Starship-class rockets and a system that starts operating in 2050 (CLM-0662). It needs 2,321 launches to deliver 5.9 million kg for one design, and 3,960 to deliver 10 million kg for the other. Twelve of every 13 launches only refuel payloads in LEO for the climb to GEO (CLM-0144). This is a modelled estimate, not a programme cost.
What is disputed or uncertain. The launch price itself. Low figures all rest on forecasts or assumptions. The company Virtus Solis, in its own 2024 analysis, estimates USD 665/kg to LEO for a Starship that is not reused, and expects launch costs in the USD 500/kg range within a decade (CLM-0532). A 2010 paper forecast USD 403 to 450/kg for a fully reusable launcher, but only if the satellite programme itself supplied the flight rate, so the argument is circular (CLM-0194). Two Frazer-Nash studies, for the UK government in 2021 (in 2018 prices) and for the European Space Agency in 2022, assume GBP 358 to 2,410 and EUR 454 to 3,301 per kg to GEO (CLM-0382).
The route to GEO matters as much as the price. By calculation from NASA's own figures, the disputed figure in NASA's study is its transfer plan, not its launch price. NASA assumes USD 1,000/kg to LEO, less a 15 per cent discount for buying launches in bulk, which is USD 850/kg. The effective cost delivered to GEO is USD 11,050/kg. Almost all of that thirteen-fold rise comes from twelve tanker launches, which carry only fuel, for each payload launch (CLM-0600).
Electric transfer removes the largest single cost term (CLM-0601). In it, electric tugs move payloads between orbits instead of refuelling. NASA's sensitivity run reports 62 per cent total cost savings for its electric variant (CLM-0601). This site's own calculation, built from NASA's inputs, removes the refuelling launches and applies a 17.2 per cent mass penalty for electric propulsion. Levelised cost, the lifetime cost per unit of electricity, falls from 0.6231 to 0.2069 USD/kWh, a 67 per cent cut. That is still four to ten times the 0.02 to 0.05 USD/kWh ground-based comparator, and the two results are not fully independent (CLM-0601). NASA also modelled a chemical route direct to GEO, in which Starship carries its own fuel all the way and is not reused. Lifecycle cost falls by at least 42 and 47 per cent for the two designs, but greenhouse gas emissions fall by only 8 and 9 per cent, because many more Starships must be built (CLM-0666).
The idea of electric transfer is old. A 1980 study by NASA's Jet Propulsion Laboratory (JPL) modelled moving 2,000 tonnes with 150 MW of electric thrusters in 160 to 213 days, using thruster performance that was projected, not demonstrated (CLM-0700). The 1981 reference design's electric ferry, a slow solar-powered ion-thruster vehicle, would have burned about 0.13 kg of propellant per kg delivered, by division of its stated figures (CLM-1026). Its 120 cm thruster was larger than any fully qualified thruster of the time. A chemical stage, in a workshop figure for a Boeing concept, would have needed 280 flights per satellite (CLM-1026).
Other figures are dated, unclear or untested. A second 2010 paper assumed USD 10,000/kg to LEO, scaled from Ariane V prices, and reached at least USD 25 billion per GW for launch alone. Its author called that uneconomic (CLM-0199). A 2025 Chinese design prints a transport rate of USD 1,000/kg, but division of its own totals gives USD 482/kg, and its basis year is unstated. By simple division, NASA's USD 11,050/kg to GEO is about 11 and 23 times these. All are assumptions, not prices anyone has paid (CLM-0698). Orbit choice also matters. Virtus Solis's own unaudited model, at 100 reuses of each rocket, gives USD 9/kg to LEO, USD 26/kg to its own Molniya orbit (a long elliptical orbit) and USD 35/kg to GEO (CLM-0668).
The 1979 to 1980 programme gave low figures, all estimates or targets. A 1979 NASA cost data book priced one flight of the reference heavy-lift launcher, the large rocket that would carry the satellite parts, at USD 10.1 million in 1977 dollars. Dividing that price by the launcher's net payload gives USD 27.0/kg to LEO. The estimate assumes no vehicle ever fails and carries no spare vehicles (CLM-1024). An independent 1980 review judged those costs reasonable for an early stage, once adjusted for optimistic scenarios. It added reserve vehicles because the plan assumed no failures. Per-satellite transport cost rose from USD 2,802 million to USD 3,113 million in 1977 dollars, with a range of minus 15 to plus 35 per cent (CLM-1030). A January 1980 workshop set a target of USD 30/kg to LEO in 1979 dollars and called the programme's timing clearly unrealistic for space transport (CLM-1025).
What is missing. No cited source gives a measured or contracted price per kg to GEO. No cited source reports a launch contract at the scale and rate these systems need at any of the prices quoted (CLM-0382). No cited source reports a flight of electric transfer at the scale these systems need.
Read next. Launch price per kilogram: what the models assume. Which assumption drives the cost spread. Building it in orbit. What it would cost.
Records
75 of the 86 records tagged to this layer are published. The rest are not yet published. A record is published only after a second reader has checked it and it has passed every publication check. What the gate checks.
| Record | In plain language | Tier | Confidence |
|---|---|---|---|
| CLM-0019 | The report sets out Space Solar's plan: a small in-orbit test, then 31 megawatts in 2030, 150 megawatts in 2033, and 650 megawatts in geostationary orbit in 2036. | T4 | MED |
| CLM-0144 | A NASA study found that launching everything into space is by far the biggest cost of a space solar power system, and that most of those launches would just be carrying fuel to move earlier payloads from a low orbit up to the final, much higher orbit, not carrying useful hardware. | T3 | HIGH |
| CLM-0176 | The launch-cost range that drives most of this study's cost uncertainty is not based on any launch that has actually happened - for Starship, a rocket not yet in service, it assumes a launch costs about the same as a Falcon Heavy launch did in 2021 (100 million US dollars), and it also uses a British spaceplane concept (SABRE) that has never flown. | T4 | HIGH |
| CLM-0181 | The 9.4-cents and 3.8-cents per kWh figures both depend on launch prices that do not exist yet - they are extrapolated 10 and 20 years into the future from a historical cost-decline trend, using SpaceX's not-yet-finalised Starship costs and a design still based on today's Falcon 9 hardware costs. | T2 | MED |
| CLM-0187 | The company's own 2024 analysis estimates that a single, non-reused Starship launch to low orbit would cost about $665 per kilogram, and projects (using two very different learning-rate scenarios) that this could fall to somewhere between about $12 and $614 per kilogram within ten years, with the company itself expecting something close to $500/kg. | T4 | MED |
| CLM-0194 | This 2010 paper predicts that if enough solar power satellites were built to justify mass-producing reusable rockets, launch could eventually cost around USD 400-450 per kilogram, against over USD 10,000 per kilogram at the time of writing, and this would add only about 2 US cents per kilowatt-hour to the price of the electricity produced. | T5 | MED |
| CLM-0195 | In 2025 the whole world launched about 2,712 metric tons of satellites into orbit across 325 launches. A single 2010-era plan for solar power satellites assumed that, at its busiest point, over 160,000 metric tons a year and thousands of launches a year would be needed just for that one program. Real-world 2025 launch activity is far below that assumed scale. | T5 | MED |
| CLM-0199 | The paper estimates that just launching the parts for a 1-gigawatt space solar power satellite would cost at least $25 billion, using 2010-era, pre-reusable-rocket launch prices scaled up from the Ariane V rocket. The author calls this launch cost alone "uneconomic." Adding the cost of building the satellite and the ground antenna brings the total to about $30 billion per gigawatt, which is far above the $1-5 billion per gigawatt the paper cites for building a new fossil-fuel or nuclear power plant. | T5 | HIGH |
| CLM-0281 | The study tested how much the cost of launching material into space changes the price of space solar power. It used launch-cost data from about 2022. The report says that if launch costs fell to about 400 euros per kilogram, which it describes as similar to costs seen for reusable SpaceX rockets at the time, space solar power could become highly competitive with other ways of generating electricity. The report does not give a source for the 400 euro figure. | T4 | MED |
| CLM-0297 | The low electricity costs in a 2025 Caltech study rest on two assumptions among others. First, it assumes that SpaceX's Starship will in time launch cargo for about 7 million dollars a flight, falling to 3 million, which works out at roughly 128 dollars and then 55 dollars per kilogram. Those are the authors' own projections, built on the way SpaceX said in 2020 that Starship would reach geostationary orbit and on the long-run fall in launch costs, not prices anyone has paid. Second, it assumes that the money to build the system costs 2 percent a year (a 2 percent discount rate), taken from a US government energy memorandum, which the paper itself says reflects one country's funding arrangements at one moment. With the costs and hardware available when it was published in 2025, the same study's own figure is about 778 US cents per kilowatt-hour. | T2 | MED |
| CLM-0450 | An economic model from about 2011 of a small, first-of-a-kind demonstration solar power satellite found its electricity would cost over 23 USD per kilowatt-hour if privately financed, against roughly 1 USD per kilowatt-hour that the source uses for comparison (generator power at US forward military bases, where its own estimates run from about 0.9 to 27 USD); only full government funding of both development and hardware brought the price down to 0.15 USD per kilowatt-hour, which the authors say may then be competitive on optimistic ground-system costs, in a case they judge unlikely. | T5 | MED |
| CLM-0517 | Every date in the plan -- the ground demo (2026), the demo mission (2027-28), 2030, 2033 and 2036 -- is a hope, not a booking, and the report that states them says so itself. | T4 | HIGH |
| CLM-0528 | NASA's assumptions imply a high cost per kilogram delivered to the power station's actual orbit, mainly because NASA assumes every launch carrying hardware needs twelve extra fuel-only launches to refuel it for the climb from low orbit. | T0 | HIGH |
| CLM-0531 | Neither the UK nor the US figure for what it costs to get a kilogram of hardware into the power station's real orbit is based on an actual, completed transaction. Both are assumptions about future launches, and NASA says it makes no claim that its assumed launch price is reliable. For the same rocket and the same starting price per launch, the two figures differ mainly in how hardware is assumed to get from low orbit to its final orbit, and that is what changes the number of launches needed. | T4 | MED |
| CLM-0532 | A different space-solar-power company's own 2024 analysis estimates that a single non-reused Starship launch to low orbit would cost about $665 per kilogram, and that costs could fall toward $500/kg within a decade. | T4 | MED |
| CLM-0533 | All the rockets in the world together put about 2.7 million kilograms into orbit in 2025, about a fourteenth of the mass of one solar power satellite design from 1978 (about a thirteenth for the main 1978 reference design). | T3 | HIGH |
| CLM-0534 | SpaceX's published Falcon 9 price is lower per launch than the 100 million dollars both the US and UK studies assumed, but higher per kilogram, because Falcon 9 carries far less than the rocket those studies assumed. A real government order in late 2025 for five missions averaged more than 100 million dollars each. Neither figure allows for getting from low orbit up to the power station's real orbit. | T6 | MED |
| CLM-0535 | By late July 2026, after 13 test flights, SpaceX's Starship rocket had still not been launched into low Earth orbit, and its test of transferring fuel between two of its craft in space had not yet flown. It flew five times in 2025. | T6 | MED |
| CLM-0600 | NASA's launch price was optimistic, not pessimistic. The expensive part is its assumption that each payload needs twelve refuelling flights, which multiplies the cost thirteen times. | T0 | HIGH |
| CLM-0601 | In one model, swapping refuelling flights for electric-propulsion tugs cuts the electricity cost by about two thirds. NASA's own analysis reports 62 per cent total cost savings for its electric-propulsion variant, and a critic said that using tugs with electric propulsion would be a far more efficient approach. The three are not fully independent, because the model uses NASA's own inputs. | T0 | MED |
| CLM-0660 | The 2019 CASSIOPeiA paper does not discuss electric propulsion for getting the satellite to its orbit. It only prices delivery using ordinary rocket-fuel-based transfer methods. | T2 | HIGH |
| CLM-0662 | NASA's own report lays out a timeline: build in the 2030s, launch and move to the final high orbit in the 2040s, then run the system from 2050 to 2080. | T3 | HIGH |
| CLM-0666 | NASA also modelled a third option: a rocket that flies itself all the way to the final orbit without refuelling, at the cost of carrying so much of its own fuel that it can only deliver about a fifth of its normal cargo. This cuts cost a lot but barely cuts emissions, because so many more rockets have to be built. | T3 | HIGH |
| CLM-0667 | One company's design deliberately avoids the standard high orbit used by other designs, because it believes waiting for compatibility with existing satellites there would delay deployment by decades. | T4 | MED |
| CLM-0668 | The same company's own numbers show that, using the identical rocket and the identical (chemical) engine type throughout, simply choosing a higher orbit roughly quadruples the cost per kilogram - a separate effect from which propulsion type is used. | T4 | MED |
| CLM-0675 | Some real satellites use a mixed approach: a normal rocket engine does most of the work of reaching high orbit, and small electric thrusters only fine-tune the final position. This is much faster than doing the whole trip electrically: 4 to 74 days on the eleven flights reported. | T4 | HIGH |
| CLM-0687 | The Chinese design says how it gets to orbit. Rockets carry the parts to a low orbit. A reusable space tug then moves each part up to the high orbit, where they are put together. The paper says that assembling it high up lowers the risk of hitting space debris, because there is much less debris there. The tug comes back down to be refuelled and to have its solar panels swapped. The design does not say whether the tug burns fuel or uses electric thrusters. | T2 | HIGH |
| CLM-0688 | The Chinese design shields the satellite parts from radiation during the climb to high orbit, using the tug itself as the shield. It also plans to replace the tug's own solar panels in low orbit, along with refuelling it, so that the tug can be reused. | T2 | HIGH |
| CLM-0698 | The Chinese cost table states a transport price of 1,000 dollars per kilogram in its column heading, but its own numbers only work out at about 482 dollars per kilogram. Every row shows the same mismatch, so it is not a rounding error. Either way the figure is far below NASA's assumed 11,050 dollars per kilogram - between 11 and 23 times below, depending which of the two you use. | T0 | MED |
| CLM-0700 | A 1980 JPL paper already worked out how to move a two-thousand-tonne payload from low orbit to high orbit using electric thrusters. It needed 150 megawatts of electrical power and took between 160 and 213 days depending on which thruster was used. The magnetoplasmadynamic option needed only 23 thrusters against 920 to 2,000 for the ion options. | T3 | HIGH |
| CLM-0701 | The 1980 study assumes each kilogram being moved has 75 watts of electrical power pushing it. One real electric satellite manages between about 2 and 9 watts per kilogram of its whole launch weight. The study's figure is 8 to 33 times that, but it counts only the cargo, so on a like-for-like count the gap would be smaller. That assumption, more than the thruster type, is why its travel times look so short for such a huge payload. | T0 | HIGH |
| CLM-0702 | Electric trips from a low orbit to a high one took four to seven months on real flights and in most models held here, and NASA's four-month figure is at the fast end of that. One European study expects at least 20 months for its modules, because the time depends on how much thrust each tonne gets. | T4 | MED |
| CLM-0714 | The 2021 UK study by Frazer-Nash Consultancy proposed that the satellite fly itself to its final orbit, using its own solar panels to run its own electric thrusters. Chemical tugs would take the parts only partway, to about 5,900 km, just above the inner radiation belt, where the satellite would be built. The study said the plan needed further work and gave no figures for the self-powered trip. | T4 | HIGH |
| CLM-0715 | The 2021 UK study assumed one extra fuel launch for every payload launch; NASA's 2024 study assumed twelve. The reason, which neither study states, is not that they disagree about the price of a rocket: the UK plan used chemical rockets only part of the way up, to about 5,900 km, and then switched to electric, while NASA's used chemical rockets all the way to the top. The two studies also assumed different amounts of cargo reach the top per launch. | T4 | HIGH |
| CLM-0964 | To build two of these satellites a year, about 300 tonnes of material had to arrive at the orbital construction site every day. Getting it there was over a third of the whole cost. | T3 | HIGH |
| CLM-0987 | They built in high orbit not because it was cheaper - the 1978 numbers said low orbit was - but because a half-built satellite in low orbit gets pulled about by gravity gradients and drag, cools every time it passes into shadow, and cannot be flown up to high orbit in one piece without breaking. | T3 | HIGH |
| CLM-1023 | The 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 and turnaround times, deliberately gives no costs, and ends by recommending a launcher with a quarter to a third of the payload. | T3 | HIGH |
| CLM-1024 | The 1979 government estimate put a heavy-lift flight at about ten million dollars of the day, most of it people refurbishing the vehicle, which works out at about thirty 1979 dollars for every kilogram put into low orbit. That is the number the programme's later cost goal was built on. | T3 | HIGH |
| CLM-1025 | In 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 the same breath that the programme's schedule could not be met. | T3 | HIGH |
| CLM-1026 | 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. | T3 | HIGH |
| CLM-1027 | Getting 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 with fuel the slow electric ferry had carried up. Counted fully, moving one worker's year of labour into orbit cost about a million 1977 dollars. | T3 | HIGH |
| CLM-1028 | Building the rockets was priced at seventeen billion 1977 dollars and running them at about 2.8 billion per satellite, or roughly sixty 1979 dollars for every kilogram of satellite delivered to its final orbit. Most of that was the launcher; the electric ferry was a fifth. | T3 | HIGH |
| CLM-1029 | In 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 needed to develop the system, and it noted that the whole programme through the first satellite cost about what NASA had spent from its founding through Apollo. | T3 | HIGH |
| CLM-1030 | The independent 1980 cost review said the government's rocket numbers were fair for the stage the programme was at, then added spare vehicles because the plan assumed nothing would ever fail, roughly doubled the risk on the electric ferry because its unit price assumed a factory that did not exist, struck out the dedicated crew launcher, and put the running cost about eleven per cent higher with a much wider error band. | T3 | HIGH |
| CLM-1031 | A 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 one, but would save five billion dollars up front and add only three per cent to the cost of each satellite. By 1981 everyone involved wanted it. | T3 | HIGH |
| CLM-1032 | If the ferry's solar cells could not be repaired in flight it would wear out in three trips and the cost per kilogram would rise by about a third; thicker glass would fix that. A ten-minute delay restarting the engines every orbit cost more than the heat of being near Earth, and a chemical ferry would cost twice as much. | T3 | MED |
| CLM-1033 | At 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 its oxygen, and making the hydrogen by splitting water would have consumed about half the output of one of the satellites being launched. NASA's own report gives two different figures for how much fuel that is. | T3 | MED |
| CLM-1034 | The programme's transportation workshop said the schedule was probably unrealistic, and the programme's cost reviewer said the launcher fleet was too small for it: about one launch a day on a five-and-a-half-day turnaround with no reserve vehicles, and a fleet of slow electric ferries with no slack for accidents. | T3 | HIGH |
| CLM-1035 | In 1981 NASA priced a satellite at 11.5 billion 1977 dollars and the road to the first one at 102 billion, said it was not an official figure, and built the transport line on a launch price that works out at about 24 of those dollars per kilogram to orbit. | T3 | HIGH |
| CLM-1057 | The safety study's own picture of the system: about $13 billion of hardware per satellite in 1978 money, 640 people in orbit for six months to build each one, forty heavy launches per gigawatt, a launch site loud at six kilometres and windows rattling at 125, and one rocket failure that could kill a thousand. | T3 | HIGH |
| CLM-1060 | The 1980 review did not agree with itself on how much of a satellite's cost was rockets: one paper said over a third, the programme's own table said a quarter of each satellite but nearly half of the money to get to the first one, and one paper's launch rate was double everyone else's. | T3 | HIGH |
| CLM-1062 | In 1980 the launch vehicle that everything was costed on was said by its own designers to be arbitrarily big, and they proposed a rocket a third the size that would save five billion dollars up front for a three per cent higher running cost. | T3 | HIGH |
| CLM-1069 | Each launch would put about ten tonnes of nitrogen dioxide into a cloud over the pad, enough to breach a one-hour air standard on a bad day but not on its own, and make a shower of rain about as acid as ordinary polluted rain; the programme's own papers disagreed whether that happened 375 or 500 times a year. | T3 | MED |
| CLM-1070 | Nobody in 1980 agreed whether the ion engines' argon would be caught by the earth's magnetic field or escape: one group had most of it caught within twenty seconds, another had all but a few per cent escaping, and the third had a sixth raining back into the atmosphere. | T3 | MED |
| CLM-1199 | On its long, looping 12-hour orbit each array hangs over one region for about 11 and a half hours, then on the next loop serves a region about halfway round the world; the company plans 16 of them. | T4 | MED |
| CLM-1223 | In 2019 China's state news agency said the country's main space-technology academy planned a megawatt-scale solar power station in space by 2035, weighing about 200 tonnes, and was spending about 28 million US dollars on a ground test site in Chongqing. | T5 | MED |
| CLM-1245 | In 2016 a senior Chinese military official told state media that China planned to use the space between the Earth and the Moon for solar power after its space station was built, but that a full-scale plant, over 10,000 tonnes, was beyond current technology. | T5 | MED |
| CLM-1246 | In 2019 a Chinese state science paper said China had started building a test base in Chongqing, planned high-altitude solar stations by 2025, a megawatt-scale test station in space from 2030 and the ability to build a gigawatt commercial plant by 2050. | T5 | MED |
| CLM-1249 | Japan's December 2025 space roadmap plans to launch a solar power demonstration satellite, OHISAMA, on a private Kairos rocket in the year from April 2026, to beam power from low orbit to the ground. | T3 | HIGH |
| CLM-1272 | In 2000 NASA sketched a path from small demonstrations around 2006 to a first full-size power satellite prototype between 2025 and 2035, and very large systems after 2050. None of it was funded, and none of the dated steps has happened in a held source. | T5 | HIGH |
| CLM-1367 | A long spinning cable in low orbit dips its end down to 150 km, grabs a cargo pod from a very fast plane, and flings it towards a high orbit. | T3 | MED |
| CLM-1368 | The study found a 600 to 900 km cable works best. Shorter ones jerk the cargo too hard, longer ones get too heavy. Its first design spun faster than it needed to. | T3 | MED |
| CLM-1369 | The design is a ribbon about 100,000 km long, fixed to a sea platform near the equator, that stays over the same spot as the Earth turns. Without avoidance, something in orbit would hit it about once a year. | T3 | MED |
| CLM-1370 | The cable needs a material about 30 times stronger than steel. In 2003 only carbon nanotubes looked able to get there, and real fibres were nowhere near yet. | T3 | MED |
| CLM-1389 | Getting a kilogram into orbit has become more than 20 times cheaper since 1960, and the study finds the cost falls by about a fifth every time the total mass ever launched doubles. | T2 | MED |
| CLM-1390 | The study expects launch to keep getting cheaper, to about a tenth of today's average by 2040, but says market power and space debris could slow that. | T2 | MED |
| CLM-1437 | A satellite in geostationary orbit, about 36,000 km up, goes round the Earth once in the time the Earth takes to turn once, which is just under 24 hours. So it stays over the same spot on the ground. | T0 | MED |
| CLM-1438 | The ring of geostationary orbit lies over the Earth's equator. That ring is tilted by about 23.4 degrees to the flat plane in which the Earth travels round the Sun. So for most of the year the Sun is above or below the ring, and it lines up with the ring only around the two equinoxes. | T3 | MED |
| CLM-1443 | The 2021 study for the UK government says the leading designs need no new materials, but that building them at a sensible cost needs two things that are not yet mature: robots that assemble large structures in orbit, and cheap reusable rockets. It says both are developing fast, that the whole system is at an early stage with considerable engineering risk, and that a programme of design and technology demonstration could address that risk. | T4 | MED |
| CLM-1445 | The 2021 study for the UK government reports that supporters of space solar power say it has become workable and affordable in the last ten years, after long being seen as attractive but too expensive. The study lists five reasons for the renewed interest: the push to Net Zero, launch costs that have fallen sharply and are expected to keep falling, modular designs built for mass production, maturing solar cells, wireless power and space robots, and other countries' strategic interest. It gives no figures for these on that page. | T4 | MED |
| CLM-1448 | In 1979, the planners of a space solar power programme expected launch to low orbit to cost about 140 dollars a kilogram in today's money, on a large rocket they planned to fly hundreds of times. A 2026 study puts the average cost over all launches in 2025 at about 3,900 dollars a kilogram in today's money, about 28 times as much. The two numbers are different kinds of figure: one is a forecast for one planned rocket, the other an average over every rocket that flew that year. | T0 | MED |
| CLM-1450 | SpaceX's price sheet lists a Falcon 9 launch at 74 million dollars, and 22,000 kilograms as the most it can carry to low orbit if the rocket is not recovered. Using those listed figures with the US study's own way of counting the extra launches needed to reach the power station's orbit gives a cost per kilogram about four times what the US study's own assumptions give, and the UK study's lowest input would need launches about ninety times cheaper than that listed figure. Both studies turn to electric propulsion for part of the climb, NASA only in the case where it finds a competitive cost, and this has not been shown at power-station scale. | T6 | LOW |
| CLM-1453 | A 2021 UK study estimated what it would cost to carry satellites to high orbit on two reusable launchers: 3,260 dollars a kilogram for SpaceX Starship and 1,340 pounds a kilogram for the British SABRE spaceplane. The study does not set the two side by side in one currency, but converted at any of the exchange rates it lists, the Starship figure is the higher. The cost range its model actually uses runs from 358 to 2,410 pounds a kilogram. | T4 | MED |
| CLM-1460 | When a US military satellite's main engine for climbing to its high orbit failed in 2010, press reports from 2010 and 2012 say its small chemical thrusters and then its electric thrusters lifted it the rest of the way; on their dates the electric thrusters were in use for about a year, two months longer than the recovery plan expected, and the satellite reached its final orbit about 14 months after launch. | T5 | LOW |
| CLM-1468 | The basic idea, a solar power satellite climbing to its final orbit on electric engines run by solar panels it carries, with no separate fuel tanker, is real: it has flown on communications satellites, though not at the scale of a power station. A 2013 design does it with a separate, smaller set of panels. The stronger version, where the satellite's own main panels run the engines, has been proposed, for example by a 1977 US study, which found the panels used for the trip would be badly damaged on the way, and by a 2021 UK study for the last part of the climb only, after chemical stages carry the parts past the inner radiation belt. None of these designs has flown. | T0 | MED |