Re: Bill you missed out on a business opportunity

Bill Brown

As often is the case, the pioneers in technology are too far in advance of demand. All I see here is a small rocket launched from a not-very-high hot air balloon. I do wish them success and hopefully they have worked out the math for the optimum liftoff altitude and rocket thrust (and weight) necessary to achieve orbit. There have been dozens of Rockoon startups with fancy CGI graphics, a nicely edited video and great background music who then disappear when they find funding is hard to raise. A hot-air-balloon (or high-altitude zero pressure balloon) would have to be capable of lifting thousands of pounds of rocket to place a small toaster-size payload into LEO orbit and would have to be above 70,000 feet to make it worthwhile. A rockoon is indeed a great first stage replacement. The rocket can be about 25 percent of the weight of an equivalent ground-based launch plus the rocket motor nozzle is more efficient in a near vacuum BUT it is also much harder to ignite in a near vacuum and -60 deg temperatures. We did work out how to do that using a series of weather balloon flights. A small rocket can make it into Space itself but it would come right back down again. Very useful for microgravity and sounding rocket experiments. Plus it gives you the flexibility of moving your launchsite around on a boat which we proved out 20 years ago since you can cancel out the surface winds completely by steering the boat along with the wind (up to the speed limitation of the boat). James Van Allen sent some of his rockoons thousands of miles into Space but didn't achieve orbital velocity and he also did most of his flights from the decks of Navy ships. That's where you need a much heavier rocket to achieve orbit, even with a Rockoon.

They seem to imply that they will be using a hot air balloon at 58,000 feet to launch their rockoon. While I was at the NearSpace Conference in Poland I had to pleasure to hear a talk about a fellow who took a hot-air balloon to 32,000 feet and beyond. It took an enormous redesign of their propane burners to work at that altitude and even after all their design efforts they still failed to keep burning after they got close to their altitude goal. I did find a story about a balloon pilot in India who made it to 69850 feet but the hot air balloon envelope was enormous and likely not capable of lifting thousands of pounds of rocket in addition.

The available launchsites for a Rockoon are very limited. Basically Black Rock Desert in Nevada, Spaceport America in New Mexico, some of the larger military bases and even a possibility in Sheboygan WI across Lake Michigan. However you cannot go past the range limits which is a real problem for a high altitude balloon and even worse you would have to prove that your rocket will land within the range after going into Space and back if it fails to achieve orbit. We solved that problem by heading out to sea on a large oil supply boat and had to be 200 miles from the coastline to launch the rocket. And yes we had FAA permission and also had to coordinate with the Coast Guard, the Navy and the Air Force. It actually took longer to get permission from all of these agencies than it did to design and build the Rockoon system. We flew a 400 pound rocket from a 500,000 cubic foot Raven zero-pressure took 33 tanks of helium.

 So it boils down to whether a hot air balloon of that magnitude and flight logistics combined with the range limitations is a cost effective way to launch small satellites with a 25 percent lighter-weight rocket than a ground-based rocket. 

- Bill WB8ELK

-----Original Message-----
From: Zack Clobes W0ZC <zclobes@...>
To: GPSL <>
Sent: Wed, Feb 13, 2019 6:02 pm
Subject: [GPSL] Bill you missed out on a business opportunity

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