New smallsat launcher start-up.

On Sunday, September 28, 2014 4:22:40 AM UTC+13, Robert Clark wrote:
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In article ,

William Mook wrote:





The weight of the tank is such that a tank that carries 11.9 kg masses 6.1

kg. So, to carry 171 kg of hydrogen requires 2,442.9 litres of storage

volume in a take that weighs 87.7 kg!



http://www.the-linde-group.com/inter...bal/en/images/

HydrogenBrochure_EN14_10196.pdf



Now, on the other hand, a Lycoming 0-360 masses 117 kg and has another 86

kg

of other machinery attached to it. A total of 203 kg. A 270 kW DC

electric

motor masses only 65 kg, has none of the machinery attached to it, and

thus,

is 138 kg lighter! More than making up the 87.7 kg weight of the fuel

tanks.

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"William Mook" wrote in message

...







Overlooked is the size of the tankage required to pack the LH2. As I

posted earlier,



Nonsense. The tankage was included in the calculation.



just the tanks would occupy the useful part of the

aircraft.



Real engineers that have designed built and tested real hydrogen fuelled

aircraft and hydrogen fuelled vehicles, like the BMW Hydrogen 7 and Boeing's

Phantom Eye and Boeing's Hydrogen Fuel Cell aircraft, find the overall mass

is less since electric motors and fuel cells mass vastly less than thermal

engines when combined with the mass of their air handling and exhaust

systems.

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That ratio of the weight of the fuel carried compared to the weight of the
tank for hydrogen at 2 to 1 is quite poor.

US DOE reports that liquid hydrogen tank weight vs. liquid hydrogen weight in 2014 is 30% or 0.3 not 2. I used 0.51 which was an older figure. So, the weights I quoted were even higher.

For kerosene it's in the range of
100 to 1.

More like 28 to 1, when you include the same fuelling features.

The Lycoming O-360 piston-engine is 1950's technology, not very efficient
in regards to the weight of the engine compared to the horsepower.

True.

Modern
jet engines are an order of magnitude better in regards to the power they
put out compared to their weight.

Yet, if we're going to do a unit for unit replacement, we're not using either. We're using an electric motor.

It's the weight of the systems for a
hydrogen-fueled aircraft that is the problem.

Its not a problem. In a long distance airliner about 40% take off weight is fuel. At 43.2 MJ/kg for Jet fuel and 141.8 MJ/kg for hydrogen you need only 0.3 kg of hydrogen for every kg of jet fuel. Adding 30% to the hydrogen figure and 3% to the Jet fuel figure to account for tanks, we have an overall change of 0.39 that of Jet fuel, or a reduction to 15.6% of take off weight for the fuel system - with no engine changes.

Now, if we take into account that a high bypass turbofan can be made an ALL bypass electric turbofan - we can double fuel efficiency! Which reduces take off weight for the same range to about 10% that of jet fuel. Finally, we'd likely increase the range of the aircraft as well as the payload at this point.

There's no reason whatever not to use hydrogen, once a supply is developed using nuclear fusion - either natural (solar power) or artificial (Jetter Cycle)



Bob Clark

Element Specifications

7.4121 Length
1.3275 Diameter
104.6 Empty Wt
3000.0 GLOW
2.1843 LOX Vol
2.4842 LOW Wt
5.9109 LH2 Vol
0.4195 LH2 Wt

A miniature external tank that's 7,412.1 mm long and 1,327.5 mm in diameter and weighs only 104.6 kg. It carries 2,184.3 litres of LOX totalling 2,484.2 kg along with 5911.0 litres of LH2 totalling 419.5 kg. It has a zero height annular aerospike engine at its base that produces 40 kN of thrust. The engine adds another 55.7 kg to the take off weight of the system. Another 25 kg includes inflatable wings and rudder that permit the empty tank to glide considerable distance once it slows to subsonic speed.

Tank GLOW: 104.6 kg
Engine: 55.7 kg
Wing: 25.0 kg

185.3 kg TOTAL INERT GLOW

LOX: 2,484.2 kg
LH2: 419.5 kg

2,903.7 kg TOTAL PROPELLANT GLOW

3,095.0 kg TOTAL ELEMENT WEIGHT

420 sec ISP - Sea-Level
455 sec ISP - Vacuum

SSTO: Single Stage performance can blast 188.65 kg to orbit!

TSTO: Strapping two tanks around a central tank and feeding propellant into the central engine from the outboard tanks improves performance. Increasing weight to LEO to 919 kg!

3STO: Strapping four tanks around these three tanks, and feeding propellant into each of the outboard tanks above, creates a three stage system consisting of seven tanks! This system is capable of lifting 1700 kg into LEO.

An inflatable wheel like station that forms a wheel 92.8 feet in diameter with a tube diameter of 9.28 feet - to form a station that rotates 3.24 RPM to produce a 1/6th gee radial acceleration. It has a floor area that's 8.5 feet by 291.5 feet - a total of 2,477.75 ft2.

This is about the size of the centrifuge of the Discovery One in the science fiction movie 2001:A Space Odyssey.

http://www.wired.com/2013/06/artific...discovery-one/

We reduce the gravity to lunar (1/6th Earth) gravity to reduce Coriolis forces and other effects.

What to do with this capacity;

In addition to a 2,477 sq ft home in space, or send 12 people into space and back, to visit their house, 1700 kg placed in LEO can send 482.75 kg to the moon one way, or 278.59 kg to the moon and bring it back to Earth.

Now, an astronaut massing 85 kg and carrying 70 kg of equipment - 145 kg total - can survive for 12 days in space, using a mechanical counter pressure suit (biosuit) and MEMS based life support hardware.

So, one or possibly two persons (depending on body size) could be sent to the moon and back.

The trans lunar injection stage consists of a 41.11 kg composite tank holding 126.52 kg of LH2 and 695.83 kg of LOX. This boosts 836.53 kg of hardware to the vicinity of the Moon.

The lunar landing stage consists of a 16.84 kg composite tank holding 51.84 kg of LH2 and 285.10 kg of LOX. This soft lands 482.75 kg of hardware on the surface of the Moon.

The lunar ascent stage consists of a 9.72 kg composite tank holding 29.91 kg of LH2 and 162.53 kg of LOX. This projects 278.59 kg of hardware from the surface of the Moon, to Earth.

With suspended animation now a reality, along with self-replicating machine systems and robot swarms,

http://labs.fhcrc.org/roth/

http://bigthink.com/ideafeed/mit-bui...ating-machines

http://www.swarmrobot.org/

This system can send people one way to Mars! (with a high probability of successful return)

Adding 4.8 km/sec to the 7.9 km/sec orbital velocity in LEO, raises the total to 12.7 km/sec. Now, since the escape velocity of Earth is 11.19 km/sec and 12.7 km/sec is greater than 11.19 km/sec - this means that a payload will have a hyperbolic excess velocity... in this case, it is

SQRT(12.70^2 - 11.19^2) = 6.00 km/sec.

Now, the propellant fraction needed to accelerate a payload by 4.8 km/sec using a rocket with an exhaust velocity of 4.462 km/sec is

u = 1 - 1/exp(4.8/4.462) = 0.65896 ~ 65.9%

So, for a 1700 kg payload in LEO we need

1700 x 0.659 = 1,120.3 kg

of propellant. With a 5% structure fraction possible with composites, a 56 kg tank is the mass budget for a stage that carries 172.3 kg of LH2 and 880 kg of LOX.

This leaves 523.7 kg payload sent to Mars with a 6 km/sec hyperbolic excess velocity.

This payload consists of an aeroshell, a parachute, and a braking rocket, to land on the Martian surface. In the end, 400 kg is landed on the Martian surface. Nearly as much as can be sent to the moon one way!

This is sufficient for two persons - if they are held in stasis during transit! This also includes several kg of solar powered microscopic self replicating robots which double their number every few hours.

An unmanned system can be sent ahead of the manned system, and a return vehicle built in-situ (on Mars). Once that has been accomplished, a manned system is sent and people returned. With a 5.03 km/sec escape velocity and a 6.00 km/sec hyperbolic excess velocity, a ship must attain 7.83 km/sec to fly back to Earth. With a 4.462 km/sec exhaust velocity we require 3,253.6 kg GLOW.

The return stage, constructed from Martian resources on Mars, consists of 162.6 kg composite tank, 414.00 kg of LH2 and 2,277.00 kg of LOX. The LH2 and LOX are manufactured from 3,726 litres of water found on Mars. (the stage could be sent ahead as suggested by Zubrin - and be part of the 400 kg payload - though reducing CO2 to CH4 using hydrogen, and processing the CH4 into carbon composites and plastics, to manufacture a stage in situ would be preferable - building a Mars home would also be of interest. 1.5 kg of carbon is reduced from the Martian atmosphere for every kg of hydrogen produced from water.

Processing enough water to return to Earth over a 2.15 year synodic cycle requires 200 milliliters of water per day be processed. Electrolyzing this much water requires a 865 watt power source. Using solar power quadruples this requirement. A 162.6 kg structure requires 108.4 kg of hydrogen - a 26% increase.

After demonstrating this capability of return, people are sent to Mars to settle (or return as they wish). (78,000 qualified people volunteered to go to Mars in a recent campaign announcing SpaceX plans)

Ships are placed on orbit over a 2.15 year synodic period. At a rate of 1 per week, 112 ships with 2 persons on board each, mean 224 people leave for Mars every 2.15 years (when the planets are aligned for Hohmann transfer). This is an average of 104 people per year.

With a population growth rate of 1.14% per year, and 104 people per year arriving on average, it takes 62 years for the internal population growth on Mars to equal the rate of arrival from Earth. Population is 9,254 by that time.

It takes 66 years to reach 10,000 persons.
It takes 103 years to reach 20,000 persons.
It takes 129 years to reach 30,000 persons.
It takes 149 years to reach 40,000 persons.
It takes 220 years to reach 100,000 persons.

If flights are interrupted after the third trip, (say due to global break down) it takes 255 years for the few on Mars to grow in numbers to 10,000 persons.

Increasing launch rate changes things the other way... and if done in large enough numbers, eases pressures on Earth.