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Cryogenic Dewar



 
 
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  #1  
Old March 24th 17, 09:11 AM posted to sci.space.policy
William Mook[_2_]
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Default Cryogenic Dewar

OTTA and HTTA dewars Following Apollo, in 1969 and 1971, under NASA contract, Beech built two ground test dewars to demonstrate techniques for very efficient storage of cryogens. They remain among the most thermally efficient dewars ever built. The oxygen thermal test article (OTTA) was 7..0 ft. diameter near-sphere with a 6,456 liter tank volume. It had fiberglass tank supports, a total of 46 silverized Mylar and silk layers in the MLI blankets and two vapor cooled shields. It was tested with liquid nitrogen and liquid hydrogen and demonstrated boil-off rate of 0.022%/day and 0.056% per day
respectively.

The hydrogen thermal test article (HTTA) was 21.8 ft long x 9.2 ft. diameter. It used all known technologies for maximizing thermal performance in a flight like dewar including fiberglass strap supports, 68 layer, aluminized Mylar MLI blankets and two vapor cooled shields. It was made from spun and welded 2219 aluminum. It was tested with liquid hydrogen and demonstrated a boil-off rate of 0.022%/day or 7.72%/year

http://iopscience.iop.org/article/10...1/1/012086/pdf

https://ntrs.nasa.gov/archive/nasa/c...0090037584.pdf

Structure fractions of 10.5% (propellant fraction of 89.5%) are achieved with this 50 year old technology. A vehicle the same shape and size as the External Tank of the Space Shuttle, with its inter-tank section removed, using the best available 1960s era technology, carry 815 metric tons of propellant and 91.6 metric tons of structure.

With an average exhaust speed of 4.3 km/sec during ascent, a SSTO system can put 13.1 metric tons into LEO.

Two elements operating in parallel puts 117 metric tons of payload.



  #2  
Old March 26th 17, 03:55 AM posted to sci.space.policy
William Mook[_2_]
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Posts: 3,840
Default Cryogenic Dewar

Zero boil off tanks are being developed by NASA
https://www.nasa.gov/mission_pages/s...ents/1270.html

This permits long duration missions with very energetic propellants like LOX/LH2.

Consider a Falcon Heavy, launching 53,000 kg into LEO bound for a mission to Ceres using LOX/LH2 propellants.

Ceres has a semi-major axis of 2.7675 AU and an orbital period of 4.6040 years.
A transfer orbit between Earth and Ceres has a semi-major axis of 1.88375 AU and an orbital period of 2.5854 years and a transfer time of 1.2927 years..

Orbital speed at Earth is 29.7658 km/sec. To transfer to Ceres requires a speed at 1 AU equal to 36.07857 km/sec which requires a hyperbolic excess velocity of 6.3128 km/sec which requires a delta vee of 4.9786 km/sec at LEO.. Using LOX/LH2 propellant with an exhaust speed of 4.3 km/sec requires a propellant fraction of 0.6752 for this kick stage. With a 53,000 kg take off weight this totals 35,785.1 kg of propellant. With a 9.5% structure fraction this leaves 12,179.9 kg of payload.

Orbital speed at Ceres is 17.8926 km/sec. When the probe arrives at Ceres it is travelling 13.0365 km/sec, requiring a 4.8561 km/sec increase in speed. With a 0.51 km/sec escape velocity for Ceres, this means that 4.8828 km/sec delta vee is required to soft land on Ceres. This requires a propellant fraction of 0.6704 for the arriving kick stage. With 12,179.9 kg stage weight, 8,164.8 kg of the total is LOX/LH2 propellant with 4.3 km/sec exhaust speed. With a 9.5% structure fraction this leaves 1,915.8 kg for payload weight.

At Ceres light intensity of 178.6 W/m2 average. This is the same level of insolation that is enjoyed by places like Boston, Minneapolis, Detroit on a much more consistent basis.

With 3,200 watts per kg of useful power produced from inflatable concentrator power systems at Ceres, and 12 MJ of power required to process a kg of raw materials in Ceres to their elemental parts and reassemble them into anything, it takes 2.976 hours ~ 3 hours to replicate a system, assuming 35% of the reduced material is useful to the construction of the replicant.

Now, Ceres masses 8.958x10^20 kg and at 35% utilisation, 3.153x10^20 kg of useful products may be produced from the entire mass of Ceres. Starting with 1,915.8 kg at the outset, this means that 57.18 doubling periods totalling 171.55 hours, or 7.148 days, converts the entire dwarf planet into 31.53 billions Stanford Toruses each massing 10 billion kg. With an internal area per Torus of 1.14 sq km, and housing a population at the same living standard and density as Monaco, 20,000 persons per Torus is supported.

http://www.nss.org/settlement/nasa/7...dy/Design.html

One torus every 70,000 km around the orbit of Ceres. To move a torus to the other side of the Orbit takes the longest time and the most energy. Namely, boost the torus to an aphelion of 3.4994 AU and have it come back to 2.7675 AU after 6.5426 years and slow into a circular orbit again. This requires 1.0598 km/sec delta vee to boost into the higher orbit, and another 1.0598 km/sec delta vee to circularise the orbit opposite Ceres. Using solar powered ion engines, with exhaust speeds of 54 km/sec - 3.693% of the space station's mass is ejected by ion rocket. 369.3 million kg of surplus shielding materials. All other systems take less time and energy to deploy. With a 36 km diameter concentrator it takes 18 days of thrusting to boost to the higher orbit, and 18 days of thrusting to circularise the orbit again on the opposite side of the Sun.

With 7.25 billion people and 31.53 billion stations, each family of four has 17 stations each station is 3,000 human level robots operating it using a self replicating utility fog throughout. This leaves 717.5 million stations scattered around the orbit of Ceres as public stations available to visited by all people everywhere.

Large solar pumped lasers are also brought back to Earth orbit, and used to boost Interplanetary Transports to Torus stations in Cerean orbit.

https://www.youtube.com/watch?v=sZNzz4SaTYk

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

https://www.youtube.com/watch?v=tf7IEVTDjng

https://www.youtube.com/watch?v=5J5bDQHQR1g

https://www.youtube.com/watch?v=0qo78R_yYFA&t=15s

https://www.youtube.com/watch?v=uVAaZVz9pDs

To transport 7.25 billion people to Cerean orbital distance in 6.5426 years requires 35.114 people per second leave Earth permanently. The world's airline industry today transport 114.077 people per second. 30.78% the rate of the airline industry.

https://en.wikipedia.org/wiki/Interp...ansport_System

With 550 tons on LEO, and a 54 km/sec exhaust speed, with laser assisted ion rockets, 1,000 persons could be sent in suspended animation, and arrive at a public space colony for training and dispatch to 17,000 surrounding space colonies. This is 3,034 launches per day. The people are placed in suspended animation after being injected with Ex-Rad and similar drugs used for radiation treatments, so they survive the radiation dosage expected, and then placed in a shielded hardshell suit. They awake upon arrival and are nursed back to health by an army of robots they own. They are then transported to their own stations.

http://www.space.com/22228-space-sta...fographic.html

Aneutronic fusion powered rockets, using Jetter fuel cycle (Lithium-6 and Deuterium, with a neutron breeding material, and a particle accelerator on a chip as a spark plug to detonate it) shaped to produce its own containment field which interacts with a magnetic nozzle efficiently to eject the high speed material efficiently, produces the next generation of constant gee ships that give mastery of the solar system.

The moon's mass 7.3477x10^22 kg is sufficient to build 7.3477x10^12 Stanford Torus cylinders. Separated by 2 km in a ring 384,400 km in diameter the disk is filled with stations out to a distance of 5.45 million km! Alternatively a band of stations orbiting the Sun at 1 AU that are 957,000 km across, would find place for all the stations described. This would be sufficient to provide nearly 1,000 Stanford Toruses per person on Earth!



  #3  
Old March 26th 17, 05:05 AM posted to sci.space.policy
William Mook[_2_]
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Posts: 3,840
Default Cryogenic Dewar

https://vimeo.com/108412303

 




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