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Rare Found Roton footage



 
 
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  #1  
Old August 4th 16, 08:35 PM posted to sci.space.policy
Greg \(Strider\) Moore
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Posts: 752
Default Rare Found Roton footage

https://i.imgur.com/dm2o6h5.gifv




Yes, a little levity:
https://www.reddit.com/r/nonononoyes...rwoahdude_ufo/

  #2  
Old August 11th 16, 06:00 PM posted to sci.space.policy
William Mook[_2_]
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Posts: 3,840
Default Rare Found Roton footage

On Friday, August 5, 2016 at 7:35:33 AM UTC+12, Greg (Strider) Moore wrote:
https://i.imgur.com/dm2o6h5.gifv




Yes, a little levity:
https://www.reddit.com/r/nonononoyes...rwoahdude_ufo/


Here's a better one;

https://www.youtube.com/watch?v=7Kp63-an2ts

and here;

https://www.youtube.com/watch?v=NX-911v7BHk

I thought a ramjet powered helicopter would be a better choice, with the ullage fuel driving a ramjet - to reduce propellant requirements of a full-on oxidizer/fuel mix of Roton and vastly better than Musk's approach of using a rocket (though a lot less hardware which is genius at reducing complexity out of the box - once the basic concept of recovery is proven - then the race will be to make it less costly in terms of payload and so forth - that's when details like this will become important)


But the advantages are clear;

Isp of LOX/LNG rocket engine is 380 seconds.
Isp of a LNG ramjet is about 3800 seconds.
Descent angle of an autogyro is about 6.6 degrees - a L/D of 8.7 to 1.0

http://naca.central.cranfield.ac.uk/...rc/rm/1111.pdf

So;

Applying a force of two gees to slow a descending stage from Mach 0.6 to Mach 0.0 in a one gee gravity field,

205.8 m/sec / 9.80665 = 21.26 seconds

You need around 5.6% of the landing weight to be propellant to achieve this goal.
Using rotor you can start with air drag to slow you to a descent speed of about Mach 0.2 or 68.6 m/sec.

IF you use a rocket to come in for a landing at that speed it takes 7 seconds of thrust - 1.84% of the landed weight must be propellant. If the rotor weight is less than the difference between 5.6% and 1.84% - then there is an argument for the rotor.

If you use a LOX/LNG rocket ON THE ROTOR - then the propellant weight falls to 0.21%. If the weight of the rockets is less than the difference in weight between 1.84% and 0.21% and a rotor was chosen above, then rockets are a go.

If you use a AIR/LNG pulsejet on the rotor - then the propellant weight falls to 0.02% !!! In fact, the LNG is built into the rotor blades themselves, to save the weight of the plumbing! lol. If pulse jets weigh more than the rockets but the difference is less than the difference between 0.21% and 0.02% - they're a go. If the pulse jets weigh less than the rockets - they're a go if rockets are a go.

https://www.faa.gov/regulations_poli...a/hfh_ch07.pdf

https://www.youtube.com/watch?v=RRrYdIqrnWY

The Robinson R-22 has a maximum take off weight of 635 kg. Its rotor system weighs 45 kg. 14.1 kg of force for each kg of weight. 7.08% - well, this is an argument against the use of a rotor of this performance for recovery! 5.6% propellant, with no added weight is really no advantage at all! In terms of weight, there is likely a lot to be said in terms of control.

A rocket with 380 sec Isp at take off burns through 7.08% of the rocket's weight accelerating to 273.6 m/sec - So, a rotor stage that accelerates a rocket to this speed or more and drops away for reuse, might be useful!

Using aerodynamics of an accelerating vehicle to to assist in achieving very high performance, is still very much a classified subject. We're all familiar with traditional variable sweep wings - like the F111

https://www.youtube.com/watch?v=9SwbpHUdBqE

Less familiar are oblique wings like on this DARPA inspired project;

https://www.youtube.com/watch?v=RbMIOvi46ro

Of course, with MEMS ram rocket arrays built into the skin of an aircraft, and addressing the array to paint moving force vectors across the surface as easily as we produce a 4K UHDTV picture on a flat screen TV, things are reduced in mass and simplified greatly.

Cryogenic fuels in zero boil off pressurised container that mass less than 2.5% of the total vehicle weight, yet produce dozens of times the thrust at lift off, provide a different approach to stage design than we have had in the past.

Anyone who uses a Dyson Air Multiplier, can see that ejecting a small quantity of air across a surface can induce a larger quantity of air to flow across that surface as well. This can be used by aerospace engineers like myself to leverage forces - and construct amazing aircraft.

The simplest sort of aircraft as far as analysis goes, is the sphere! By placing jets around the equator of a sphere, one can induce flow from the entire top surface - reducing the power required for lift. Burning the oxygen in the air induced to flow, further reduces propellant requirements! So, that's pretty awesome. No extra rotor blades! As the speed increases dynamics change. As the altitude increases, dynamics change in other ways - along with the availability of oxygen. All this is taken on board seamlessly - to create a very efficient sort of booster.

Once you understand a sphere, then you can create an oblate sphere - to mimic a wing. Changing the 'effective' shape of the wing by controlling local pressure around the wing at various speeds - allows an oblate sphere stretched in one dimension and squeezed in another - to operate efficiently as a wing at any speed - largely by changing its obliquity and angle of attack. Continuous application of force differentials to the oblate sphere - that's mashed down say 1/4th its diameter in the Y direction and stretched out 4x its diameter in the X direction to produce a winglike surface that has the same volume (though larger area) as the sphere - add nuances to the shape instead. A larger area also lets us generate more propulsive forces - while reducing propellant consumption to do it! All this translates to superior performance!

Using rotor like lift (even though an air multiplier effect is used) through Mach 1 - saves 10% propellant weight. Using atmospheric oxygen alone through Mach 3 save 15% propellant - and provides a safe means of recovery and landing for multiple stage vehicles.

A one stage vehicle using LOX/LH2 with a 4.5 km/sec exhaust speed - requires 0.8705 propellant weight to attain orbit. With a 0.0295 structure weight 0.1000 fraction (10%) of the take off weight makes it to orbit. An incredible achievement.

Now, reduce the speed requirement by 0.6 km/sec and reducing air drag and gravity losses, using aerodynamic effects, reduces this to 0.8025 propellant fraction increasing payload by 0.1680 (16.8%) an increase of 68% !!!

A SSTO without such aerodynamic assists would weigh 5,000 kg to lift 500 kg to LEO. A SSTO with such aerodynamic assist masses only 2,976.2 kg. The first is a sphere 3 meters in diameter. The second a disk 0.64 meters tall and 5.00 meters in diameter.
 




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