141–150 of 170 posts
Any more billionaires feeling left out of the space race?
Should we worry that every billionaire seems highly intent on building ways to get the heck off the planet? ... Do they know something we don't?
Dumb question: why don't they launch rockets from the tops of mountains?
Related question: Couldn't we create some sort of rocket elevator with huge and very high balloons?
http://www.zero2infinity.space/bloostar/
The low pressure lets them get away with toroidal tanks, pressure fed booster engines, and a relatively large faring. Or at least that's the plan, they haven't launched anything close to orbital class yet.
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Related question: Couldn't we create some sort of rocket elevator with huge and very high balloons?
https://what-if.xkcd.com/58/
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it's a proven design. scaled composites, which built this also built the GlobalFlyer with similar configuration. https://en.wikipedia.org/wiki/Virgin_Atlantic_GlobalFlyer
Clearly Allen and his team did the necessary engineering work, but I'm not sure the GlobalFlyer is a good example. It had a single mid-mounted engine, and had a gross, fully loaded weight of 22,000lbs. This thing has 70,000+ lbs of engines alone. The torque has to be absolutely colossal. Again, I know that much smarter people did the math, but from the eye check this does not look like a tenable design.
Imagine differing oscillations of pitch or yaw from each fuselage happening at the same time... and at just the right/wrong frequency for the connecting structure.
I'm sure I'm just overly paranoid, but often we find out long after something is built that some "little possibility" was overlooked.
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That's absolutely how I would've done it. Way cheaper to make a monster hybrid of two used 747s than to try to make a one-off custom airplane from scratch. Sure, it won't be as efficient at its job as if it were purpose-built, but you'd never get all of that R&D money back.
Once the concept is proven, once there is a real market for that, other, more efficient planes designed for bigger rockets will be built.
The really interesting question - does the modest increase in initial velocity and altitude with a boost out of the lower atmosphere make it practical to build a Single Stage To Orbit rocket? If they can, then it's an impressive achievement. If not, then it doesn't really seem worth the trouble.
More important than that is that the rocket doesn't have to punch through as dense of an atmosphere when getting up to speed. That means you don't have to reinforce the rocket as much since it's maximum dynamic pressure (maxQ) is lower giving you a better mass ratio and it means that you're not losing as much delta-v to air resistance but that's only another 100 m/s or so for a decently sized rocket like the one being launched here.
But more importantly you can design your engines so that they don't have to work at higher atmospheric pressures.
https://en.wikipedia.org/wiki/Rocket_engine_nozzle
A Merlin engine with a bell designed for taking off from sea level has a trust at sea level of 845 kN but a thrust in Vacuum of 914 kN all while burning the same amount of fuel. And a Merlin with a nozzle sized for vacuum use can go up to 934 kN when firing in vacuum, again for the same fuel flow rate.
Scaled Composites built it. It should work. Although Rutan has retired, the company goes on. It's interesting that they didn't connect the tails, like the old Lockheed P-38, but there's probably some good reason for that. Launching a Pegasus XL has to be just a demo. That's normally launched by dropping it from an old Lockheed L-1011; it doesn't need this monster. They need something bigger to launch. There was a con…
Rocket exhaust?
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Landing weights are usually a bit lower than take off weights due to the extra shock on landing. for example the a340-600 has a MTOW of 380 tons but a Max landing weight of 265 tons. Just a bit of a difference.
That's the fuel the plane takes off with. I don't know how much this beast uses, but those six engines must be burning quite a lot of it. Also, the landing gears seem to be very robust.
[1] Figures given in pounds on wikipedia, the kg version looks like a "dumb" conversion: https://en.wikipedia.org/wiki/Boeing_787_Dreamliner#Specific...
IANARS but this plane should give the remaining stage(s) four advantages: 1. +230m/s orbital velocity [1] 2. +9km launch altitude [1] 3. can launch in more weather conditions 4. 1st stage can abort mid-launch without loss of payload. Of these, the most important is the increase in launch altitude, because that means stage 2 launches in air of greatly decreased density, leading to the following efficiencies: A. a vacu…
The primary advantage of airplane launch is that you can fly to into a launch window for an orbital rendezvous. Otherwise you'd have to wait for the target's orbit to be just right w/respect to the launch site, or do a long orbit matching process. This is very useful if say you want to very quickly and quietly launch something towards another satellite. People are making comparisons with the Spruce Goose, but the Glo…
Have a plane take off with a small load and have rockets connect with it at it's highest altitude and push it into orbit.
expended stages could reconnect with another plane of the same model on the way down.