Aptera Reboot - Improved

[redpoint5]

There's nothing special about multirotors that lend themselves toward automation, as I'm always saying. They're simpler to make since they lack complexity. Their inherent instability is overcome in software. Much less efficient than having fewer but larger diameter blades.

[oil pan 4]

I think they used that many rotors because they are cheap off the shelf rotax engines.

[freebeard]

Won't someone thnik of the birds?

Imagine it had these aerospike engines:

Aerospike fan powered by Bambu Lab X1C toolhead turbine

Possibilities for sound control and it would just look cooler.

Bucky Fuller in the 1930s with his Dymaxion Omnidirectional Trasport (AKA car) predicted 'jump-jet stilts' for VTOL paired with inflatable wings.

[redpoint5]

I've been contemplating turbojet, to ramjet, to scramjet to rocket boost for orbital injection. Breathing air instead of hauling it with you is the most efficient way to gain initial speed and altitude.

[freebeard]

Tell us how it worked out when you get back.

[redpoint5]

Top Gun Maverick animated a scene where it appeared ramjet was reconfiguring for scramjet. Might be possible to make both in 1 engine.

Getting to ramjet is trickyish, but that should probably just be a railgun acceleration so one could ditch the turbojet.

[freebeard]

Consider the Skylon

Skylon is a series of concept designs for a reusable single-stage-to-orbit spaceplane by the British company Reaction Engines Limited (Reaction), using SABRE, a combined-cycle, air-breathing rocket propulsion system. The vehicle design is for a hydrogen-fuelled aircraft that would take off from a specially built reinforced runway, and accelerate to Mach 5.4 at 26 kilometres (85,000 ft) altitude (compared to typical airliner's 9–13 kilometres or 30,000–40,000 feet) using the atmosphere's oxygen before switching the engines to use the internal liquid oxygen (LOX) supply to take it into orbit.[1]
....
One of the most significant features of the Skylon's design is its powerplant, known as Synergetic Air-Breathing Rocket Engine (SABRE).[65] ... The engines are designed to operate much like a conventional jet engine to around Mach 5.5 (6,740 km/h; 4,190 mph),[63] 26 kilometres (85,302 ft) altitude, beyond which the air inlet closes and the engine operates as a highly efficient rocket to orbital speed.[63] The proposed SABRE engine is not a scramjet, but a jet engine running combined cycles of a precooled jet engine, rocket engine and ramjet.[13] Originally the key technology for this type of precooled jet engine did not exist, as it required a heat exchanger that was ten times lighter than the state of the art.[45] Research conducted since then has achieved the necessary performance.[21][66]

I forget why the jet needs to be pre-cooled but that heat exchanger is phenonemal, dropping the temp a thousand degrees in a fraction of a second or something. [cittion neeeded] of course.

edit: Here it is

https://www.space.com/32115-skylon-s...e-vehicle.html

This device precools the air entering the engine at speeds greater than four times the speed of sound (Mach 4). SABRE's precooler will cool such air from more than 1,832 degrees Fahrenheit (1,000 degrees Celsius) down to minus 238 F (minus 150 C) in one one-hundredth of a second. The oxygen in the chilled air will become liquid in the process.

I undersold it.

[Piotrsko]

In order to get enough air to burn and make any meaningful power, you have to compress it. Compress it in a supersonic venturi and boy howdy does it get hot, enough to ignite the fuel. Hypersonic is even worse, enough to melt the metals used.

Inco 625 is lots heavier than 316 ss

[redpoint5]

Yeah, an ablative engine does not lend itself towards low operating costs and reusability.

Now that has me curious if rockets use the LOX for cooling, or only the fuel?

[freebeard]

SpaceX calls it engine-enriched exhaust.