This lets you avoid the rocket equation as you don’t have to carry your own fuel. Presumably you’ll be using solar powered ion drives to gradually speed up.
Seems promising. Why not use an elongated blimp shape? Why the v?
And why can’t the space craft lift off from the ground.
> Why not use an elongated blimp shape? Why the v?
It aims to be a hypersonic vehicle. Blimps aren't brilliant for that use case. (There may also be a structural advantage since it's basically two air beams.)
> why can’t the space craft lift off from the ground
They're using a balloon to get to the edge of the atmosphere and then a lightweight craft to slowly accelerate to orbit from there. The lightweight craft would be too delicate to survive in the atmosphere. The low-altitude craft too heavy to cruise to orbit.
> Why not use an elongated blimp shape? Why the v?
For the upper stage: it would only be an airship at the start, then transition into an inflatable hypersonic lifting body before eventually reaching orbital velocity. Very similar to how a seaplane starts swimming by displacement, then transition to gliding on the water before eventually taking off.
For the lower stage: I suspect the shape is more like a branding thing, and knowledge transfer ("perhaps some of what we would have to learn about v-shaped blimps can be learned in the lower atmosphere?")
> do if the ions you’re using are collected from the atmosphere around you rather than coming from a tank on your vehicle
This [1] looks like a plasma propulsion engine [2]. They'd need to carry propellant. That said, they're pre-staging, so the traditional rocket equation doesn't apply.
Seems promising. Why not use an elongated blimp shape? Why the v?
And why can’t the space craft lift off from the ground.