Finances aside… an all-battery, wingless eVTOL is silly.
(1) Too much power: At 360kg MGTOW, the Astro will require around 65-70kW total shaft power for hover, even more for maximum forward speed. But because I’m a nice guy I’ll assent to 60kW. At the battery output, assuming 97% efficient control and 95% efficient motor (not really possible, but OK let’s use it): 65kW. That’s the same battery output to move a 2200kg Tesla Model X SUV with four people at >130km/hr, a wasteful and absurd power commitment to move 120kg of pax+payload at 70km/hr. Is it apparent now why the piloted test maintained flight well within Ground Effect, where hover power is much lower?
(2) No battery available: The best available Li ion cell today is the Panasonic/Tesla 21700, with as much as 300Wh/kg on a cell level at discharge rates of <0.5C in a narrow ambient temperature range. This figure does not include conductors, thermal management, BMS or containment. For 25 minutes of flight (Astro’s advertised number), the 65kW/25min energy need is 27kWh with no reserve (charge to 100%, discharge to 0%). A marginal reserve (95% to 5%, very detrimental to battery life) requires 30kWh, and we’re assuming that it can do this at a discharge rate of just over 2C (which Tesla cannot do). That’s 30kWh=30,000Wh, so the aircraft needs 100kg of the most capable cells available today. Even with only 10kg of thermal, control and structural hardware to support the energy source (impossible), at 110kg that’s 45% of the empty weight of the aircraft. That’s impossible. Even at 5%/year improvements in energy density between now and 2023 the battery weight is OPTMISTICALLY close to 90kg at best. We haven’t even started looking at modest challenges of fault tolerance requirements, low/high temp soak, etc.
The remaining 150kg of structure, propulsion equipment, etc just isn't in the realm of practicality. But people will believe anything.
