ARIA is paying 18 teams £70M to keep 300 watts aloft above Britain for a week

Three hundred watts held for a week is 50.4 kilowatt-hours delivered to a communications payload ^[20], and all 18 teams are being paid to make it ^[4]. What differs is how they supply it. Menapia, in Leeds, wants to rotate a fleet through the stratosphere so no single airframe has to last the full week ^[8]. "When it comes to reaching the stratosphere, the vehicles don't have very long endurance whilst up there, but that problem can be overcome by means of this fleet-level rotation system," John Mooney said ^[9]. Space Solar is working the power side instead, beaming radio-frequency energy up from the ground ^[13]. Rico Chandra, the programme director, splits the money three ways: enabling technologies such as power beaming and lightweight solar materials, aircraft integration and testing, and the communications systems a commercial fleet would need ^[7].

VFP Aerospace has given the clearest unit numbers. Six-axis drones, each built by founder Andy Cheadle at about £50,000, flown at less than £10 an hour, rotating around a 20-kilometre service route ^[12]. At that rate, a week of continuous cover costs under £1,680 in operating cost for each aircraft on station, with the airframes as the capital item ^[23].

Whether that undercuts orbit is not a question the programme sets up to answer. ARIA's case is qualitative: satellites have to survive rocket launches and radiation, and the agency thinks an aircraft holding 15 to 20 kilometres for long periods might be cheaper ^[25]. The target it has actually written down is stated in watts and days, and leaves out cost per unit of communications capacity and any launch comparison ^[26].

Then there is the budget. The £20m increase over December's estimate is 40 per cent ^[22], and ARIA attributes it to the rotorcraft proposal and the expense of flight testing ^[16]. "It's not easy to work out how costly it will be to book the drone test ranges and obtain the necessary airspace," Chandra said ^[17]. That revision arrived before any team had held the one-week endurance test ^[4].

The two screening criteria say what kind of bet this is. A project had to show the potential for a "trillion-pound socio-economic impact" and had to be unlikely to proceed without ARIA's support, and a number of well-qualified applicants were turned down ^[19]. Spread across 18 projects, £70m averages about £3.9m each ^[21], enough to fund demonstrators, and ARIA's stated hope is that at least one of the 18 engineering approaches works ^[6]. In my view the eventual comparison will turn on how much traffic 300 watts carries at that altitude, since endurance is only the minimum requirement to qualify. The counter-argument comes from Space Solar's co-founder and co-CEO. "If we are successful, it will open up new markets in a new type of telecommunications infrastructure. In rural areas it is difficult to provide the high-bandwidth connectivity that businesses need," Martin Soltau said ^[14]. If rural backhaul is the market, the price to beat is a terrestrial one.

The 40 per cent revision is still the most concrete cost number this programme has produced, and no team has published a bandwidth figure ^[22]. ARIA notes that the rotorcraft entrants are proposing a class of aircraft new to these altitudes ^[11]. "The teams are now building aircraft that have never been built before, and that is exactly something we were determined to fund," Chandra told Tech Funding News ^[10].