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The world's largest aircraft has made its first test flight:
The giant aircraft built by Stratolaunch to serve as an air-launch platform made its first flight April 13 amid questions about the future of the venture. The aircraft, the largest in the world by wingspan, took off from Mojave Air and Space Port in California at 9:58 a.m. Eastern. The plane flew for two and a half hours before landing back in Mojave, reaching a top speed of 278 kilometers per hour and altitude of 4,570 meters.
[...] [Neither Zachary Krevor, vice president of engineering at Stratolaunch,] nor Jean Floyd, the chief executive of Stratolaunch, said anything about the test flight program, including when the plane will fly again and how long the overall test program will last. The company took no questions from reporters during the call, which lasted 10 minutes.
The flight comes after a turbulent six months for the company. Its founder and principal funder, billionaire Paul Allen, passed away last October. In January, Stratolaunch announced it was abandoning development of its own launch vehicles that would have been air-launched from the plane. A company spokesman said at the time that Stratolaunch was "streamlining operations" to focus on aircraft development.
The only vehicle Stratolaunch currently plans to launch from the aircraft is Northrop Grumman's Pegasus XL, a small launch vehicle that has struggled in the commercial marketplace in recent years despite the surge in interest in small satellites. The only recent customer for the Pegasus is NASA, and problems with the rocket have delayed for months its latest mission for the agency, the ICON space science satellite.
Also at CNN.
Previously: Stratolaunch: The World's Largest Plane Rolls Out
Paul Allen's Stratolaunch Completes Key Taxi Test Days After His Death
(Score: 0) by Anonymous Coward on Sunday April 14 2019, @10:31AM (6 children)
SpaceX reusable systems makes this thing dead on arrival.
(Score: 3, Interesting) by aiwarrior on Sunday April 14 2019, @11:58AM (1 child)
I would not dismiss it. If it really is able to avoid most of the dense atmosphere for a launch this could be good. Plus the idea of having different design constraints for vacuum or low density atmosphere from a full sea level launch sounds very interesting. I think it is not dead on arrival, it is just very late to the party.
(Score: 1, Insightful) by Anonymous Coward on Monday April 15 2019, @10:05AM
Well, the speed of a rocket is lowest on its departure, and gradually rises during its flight time. Frictional losses are polynomialy dependent on speed. I am not sure how significant in overall problem space is the problem of dense atmosphere on launch. Using aerodynamic lift for a part of the journey may be a good idea for saving amount of fuel to be launched, but it is probably less efficient (greater drag, for longer time) and doesn't scale favorably with increase in launch mass - for each new bigger rocket, you need to design another, bigger air frame to carry it, and aircraft design seems slower and more work intensive than rocket design, despite the "rocket science" meme.
(Score: 4, Insightful) by FatPhil on Sunday April 14 2019, @12:05PM (3 children)
As I've said before, landing your boosters is 70s tech, so you shouldn't waste too much time stroking Musk's thrusters, he's not that cutting edge, he's just very successfully broken into a market that had forgotten how to compete and become fat and lazy on the US taxpayer's dollar, thanks to the MIC.
Great minds discuss ideas; average minds discuss events; small minds discuss people; the smallest discuss themselves
(Score: 3, Funny) by takyon on Sunday April 14 2019, @01:11PM (1 child)
Apparently not financially sound 70s tech.
And Starship's complete reusability will catch everyone with their pants down. ULA will be trying to capture Vulcan booster engines with helicopters.
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(Score: 2) by FatPhil on Monday April 15 2019, @08:30AM
Great minds discuss ideas; average minds discuss events; small minds discuss people; the smallest discuss themselves
(Score: 3, Interesting) by novak on Monday April 15 2019, @04:46AM
I'd rate that mostly false. While perhaps precisely true in the pure, mathematical sense that using air for thrust can improve Isp, there are a number of second order effects that ensure that it's not that simple, and most of these effects tend to drive up the cost as well.
First, it doesn't give any "dV" improvement, because a vehicle designed for ground launch would never be able to air launch. The highest loads, by far, on an air launched vehicle are the "twang," when it drops, plus side loading and turning (~90 degrees for current systems) under full thrust. So actually, it's a boost in Isp for a weight penalty.
Second, one of the most difficult parts of a rocket is stage separation, where the second (or later, depending on vehicle) stage separates from the previous one. This is something that's been worked on quite a long time and rarely ever fails anymore, but it does often induce high shock loading, plus it's made much easier by the fact that it's done out of atmosphere. Adding an airlaunch is essentially adding in the worst possible stage separation event, generally meaning more weight and more complexity.
Third, launch facilities are both complex and often used as a way to offload weight from the rocket- the more you can put on the ground, the better, and then make it as heavy as you want. Adding, eg, cryogenics storage and fueling capability to an air vehicle is an enormous amount of complexity. Look at what Virgin orbit is doing about that- ignoring it and dealing with boiloff (more weight penalty) because it's too tough to handle.
Fourth, you have to remember what you're comparing this air launched vehicle to. Probably, you're comparing it to something much simpler that experiences much lower loads and is marginally larger to compensate for any reduced Isp. I can tell you right now which is cheaper and easier to build and operate.
So I'd say sure, in principal, air launch is cool and could give performance benefits, but I have not seen any indication in current or advertised systems that it actually reduces launch costs. If you wanted to do that, you'd come up with clever ways to make the separation from the carrier vehicle better/easier/lower load. Stratolaunch actually does the opposite because the aircraft is huge and they don't want a rocket operating within a huge radius from it for safety reasons. It's basically a vanity project that they had to justify.
As a bonus problem with stratolaunch specifically, look how big it is. Insanely big. It could probably lift a vehicle capable of carrying ~6mt to LEO- impressive, but not even close to the size of an F9, for instance. Price per unit mass generally scales with vehicle size because some systems, like engines and avionics are expended on the second stage, and carrying more mass is the easiest way to spread out that cost. So if it's all about $/kg, strato isn't even going to be in the same league with today's RLVs, which are using 70s tech.
novak