Building a Stratospheric Balloon Launch Company with Zero 2 Infinity
spacebandits.ioThat space vehicle they show in their mockups, the conical capsule with 6 engines, can't possibly have enough delta-v for an orbital injection. For one, not enough fuel to run all those engines for a long enough time.
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 don't work for Z2I (I run Space Bandits) but that's a good point and definitely would have been worth including in the interview.
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 :)
I agree with your analysis, from the initial rocket concepts the delta-v does look lacking. One note however, I think you may be confusing your kilometers with miles - one needs around 7.8km/s for a stable LEO.
Not the OP you're replying to but you're right! I'll try to get more information on this and update once I do. Thanks!
Ballon launches are unlikely to be economically viable.
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.
Out of curiosity, what do you think will make then not viable economically? There's a lot of advantages they have compared to rockets, particularly for smallsats.
You don’t get to actually save on the expensive bits of rockets.
Within a small rounding error you need just as many and just as large rocket engines. Sure, you save a little fuel, but that’s the cheap bit. Structurally you need to handle dangling from the balloon, which means your cargo capacity is about the same size and possibly worse.
On top of that you need to both pay for the balloon and extra R&D for a complex system. If everything worked perfectly you might see a small savings per launch except the market is tiny so just breaking even on R&D is difficult. On top of that the more complex launches mean more can go wrong, meaning higher insurance costs.
Finally this is not the 80’s. Compare it to SpaceX’s reusable first stage that gives not just altitude but also velocity. Something like that is a huge advantage reducing the number of expensive bits needed to manufacture.
PS: As to dangling. When you fuel a rocket on the launch pad all the stages sit on top of each other. This means you can build a rocket that would break if sitting on it’s side, because all the forces are down before and after the engine fires.
That whole partial sum taken to infinity thing. You’re trunking off not enough of it fast enough with a balloon. Ie balloon ballast isn’t as efficient in lift as burning actual fuel. Just my off the top of my head with little knowledge thoughts though.
Sure seems viable without thinking it through at first! But I think the scale of space travel just makes it easy for intuition and first impressions to be off.
Very reminiscent of http://www.jpaerospace.com/
Really cool that they were essentially a bunch of volunteers working together to try something innovative like this - and that was before SpaceX was founded! It's a shame their rockoon prototype didn't succeed, though.
pixar's up of space companies. launches would be a lot more quiet.
Haha maybe a new tagline for them ;)