Any orbital launch must end up with the payload going 4.5 km/s at LEO (about 200 km altitude). For a classic rocket launcher, this happens after about 450 seconds. See for example the Falcon 9 velocity and altitude traces from [1]
This baloon launcher skips the altitude gain of the first 120s of a Falcon 9 launch. Not bad, but it can't skip the velocity gain - it still needs to inject 4.5 kmps delta-v.
The Paul Allen financed Stratolauncher project starts from a similar high altitude-low velocity point, but was planned to use quite a beefy rocket launched from a carrier plane to inject delta-v to the payload.
Maybe that capsule is just a suborbital vehicle. They're quite popular as a stepping stone.
[1] https://forum.nasaspaceflight.com/index.php?topic=40983.0
I found this explanation in their payload user guide of an example flight profile (excerpt):
The first stage burns for 110 seconds, upon which the vehicle reaches an altitude of 80 km and an inertial speed of 2.3 km/s. After ejecting the first stage, the vehicle reaches 400 km and 4.4 km/s in 230 seconds. Upon third and final stage separation, the third stage performs multiple firings, the first one lasting 340 seconds and reaching 600 km of altitude while still slightly below the target orbital speed. Then, after coasting and later finalizing the orbit, the payload is released.
See page 23: http://www.zero2infinity.space/wp-content/uploads/2018/01/Z2...
Thanks for raising that :)
But, what I find amusing is simply by going up you gain a little velocity from earth’s rotation via atmospheric drag. It’s kind of the opposite of everywhere else in aerospace engineering.
