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Comment by elil17 | Hacker News Reader

Could you explain what is going on in this video? Are you building a microsat launcher that gets sent off while hanging from a helicopter?

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I believe it's similar to this: https://en.wikipedia.org/wiki/Air-launch-to-orbit

The idea is to get the rocket as high as possible using conventional vehicles, which should make it easier for the rocket to reach orbit.

It was proposed as a way of launching rockets from countries that don't have access to the best spots on the planet.

I've followed ARCASpace with interest for a while, although it looks like nothing came out of it, sadly:

https://en.wikipedia.org/wiki/ARCAspace

https://en.wikipedia.org/wiki/IAR_111

https://en.wikipedia.org/wiki/Haas_(rocket)

Only problem is that altitude is the least important component of orbital space flight.

To each orbit you need to achieve roughly Mach 30 in the correct inclination, and above the bulk of the atmosphere. If your rocket can achieve Mach 30 you don’t need an altitude boost from a balloon, if your rocket can’t hit Mach 30 the balloon won’t help.

But hitting air isn't a small problem either, or is it?

It is, but it also takes time to reach those velocities. Every orbital rocket that I am aware of has a period called MaxQ, where it has to throttle back to avoid exceeding air pressure limits. But it only occurs in lower dense atmosphere and usually ends in a few seconds.

So balloon drop from high altitude avoids having MaxQ issues at all, so no throttling required (which could also make rocket engines simpler). But all the other drawbacks make air drop only useful for the tiniest of orbital payloads.

> enable accurate launch of the rocket from the balloon in the stratosphere. Even though Silverthrone is designed for launch from a balloon, its control capabilities were put to test in harsher conditions of the heavy downwash of the helicopter, to ensure it is ready for rocket launch.

Seems like this is testing the hardware that will be elevated using a balloon. The helicopter isn't part of launch plans.

Ah, so it's a tweak for sneaking the rocket beyond those thickest layers of air, interesting. My initial impression was that it might be just a clever idea to forego the need for a dedicated rocket launch pad.

Why not both? :)

A launch pad gives you the capacity for far larger rockets and payloads.

A high altitude start only allows you to tweak your rocket nozzles for minor efficiency gains.

In the video, we show a flight test of our system hanging from a helicopter - however, our actual launches will happen while hanging from a high altitude balloon, not a helicopter. The helicopter test gives us a way to test the performance of our yaw control system (to point the rocket along a desired heading) without having to do a full blown balloon launch.

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