On Sunday, August 21, 2016 at 6:37:07 AM UTC+12, Robert Clark wrote:
American Journal of Nanomaterials
Vol. 4, No. 2, 2016, pp 39-43. doi: 10.12691/ajn-4-2-2 | Research Article
From Nanoscale to Macroscale: Applications of Nanotechnology to Production
of Bulk Ultra-Strong Materials.
Robert Clark
Department of Mathematics, Widener University, Chester, United States
http://pubs.sciepub.com/ajn/4/2/2/index.html

Next stop: the space elevator.

Bob Clark

----------------------------------------------------------------------------------------------------------------------------------
Finally, nanotechnology can now fulfill its potential to revolutionize
21st-century technology, from the space elevator, to private, orbital
launchers, to 'flying cars'.
This crowdfunding campaign is to prove it:

Nanotech: from air to space.
https://www.indiegogo.com/projects/n...ce/x/13319568/
----------------------------------------------------------------------------------------------------------------------------------

Double walled carbon nanotubes were fabricated into motors over a decade ago. Recently, the power to weight has been upped, and arrays of these could power nano-scale and micro-scale machinery.

https://users.soe.ucsc.edu/~yuzvinsk.../nanomotor.php

http://www.kurzweilai.net/the-worlds...ful-nanoengine

The ability to produce megawatts per kg of weight exceeds the power density of lightweight engines like the PWR RS-24 SSME Block 2 H2 Turbopump (Brayton Cycle) 63.4 MW at 460 kg produces 138 kW/kg.

Achieving 2.8 MW per kg - when achieved - reduces the weight of this pump to 23 kg!! Meanwhile, the use of CNT reinforced combustion and thrust chambers, reduce weights there as well. While, the ability to reduce engine size automatically increases thrust to weight of the engine.

Arrays of micro scale and nano-scale batteries, capacitors, flow batteries and fuel cells, have achieved 6.8 MW to 10 MW per kg power densities.

* * *

So, it is of interest to consider the creation of a hydrogen oxygen fuel cell powered fuel pump system for a rocket - that exceeds the efficiencies and performance of conventional systems.

To produce 1.5 gees at lift off beneath a 760 tonne External Tank, requires 6 SSME firing at full thrust. This requires 380.4 MW of power be generated by hydrogen and oxygen in a fuel cell. At 85% efficiency, such a fuel cell would process

* * *

The drag equation is

F = 1/2 * rho * u^2 * Cd * A.

A space shuttle external tank shape and aerodynamic performance is well understood. The total drag area of the tank is

A = 55.899 + 274.774 * sin(theta) + 40.147 * (sin(theta))^2 + 11.883 * (sin(theta))^3

Cd of the External tank from zero speed to Mach 2.3 is 0.08

u during glide is 134.17 m/sec (300 mph)

density of air depends on altitude and is;

0 km altitude 1.2250 kg/m3
10 km altitude 0.4127 kg/m3
20 km altitude 0.0880 kg/m3
30 km altitude 0.0180 kg/m3
40 km altitude 0.0039 kg/m3
50 km altitude 0.0010 kg/m3

Which tells us something when we look at how the External Tank gets destroyed during re-entry. Basically, the tank is designed to withstand heating during ascent without causing the cryogenic liquids to boil off. It could survive modest heating during re-entry. What does the system in is it gets smashed by rapid acceleration as it falls to lower altitudes.

By modulating lift during re-entry, the tank can be maintained at reasonably high altitudes where air density is very low, and forces as well as temperature, modulated. A very modest increase in thermal protection is required if this is done, and weight is not adversely affected.

In the end, the tank is flying at 20,000 m altitude travelling at 134.17 m/sec (300 mph/ 485 kph) and flying at 2.5 degrees elevation (using inflatable wings deployed after slowing to subsonic speeds) producing a substantial controlled body lift. Hydrogen fuel is drawn from tank ullage of a zero boil off tank, and combined with atmospheric oxygen, in an array of nano-scale fuel cells, must consume 569 kW of power in four props of 142.25 kW each - a very tiny amount of power when compared to the requirements for pumps at full power!

At 20,000 meters, the tank can fly 33.4 km/kg of hydrogen ullage gas, when combined with atmospheric oxygen. At 10,000 meters the range drops to 7.1 km/kg at this speed - and power requirement increases to 2.7 MW. At sea level power rises to 7.9 MW to maintain speed and range drops to 2.4 km/kg.

A surplus of 1/2 percent of hydrogen (584.6 kg out of 116.93 metric tons of hydrogen out of 760 metric tons of propellant) is sufficient to fly the tank 19,525.6 km at 20,000 meters! This allows flying from nearly any point on Earth back to the launch centre in less than 40.3 hours following launch.

* * *

A sub-scale system is being designed that consists of seven flight elements.. Each element is shaped like a minature External Tank that is 1 meter in diameter and 6 meters long. Empty, the tank masses 57.7 kg and carries 197..3 kg of liquid hydrogen along with 1,085.0 kg of liquid oxygen. The seven elements carry 1100 kg into space (2,425 lbs). At $2.5 million per launch the system achieves a very low price point in combination with a very good profit.

The price of each tank is $890,900 - and ten articles are produced as part of the development programme. The entire programme costs $20 million and results in an ability to fly three payloads per week into LEO. 156 payloads per year earning $390 million per year on a $20 million investment.

Each tank consumes 197.3 kg of liquid hydrogen and 1,085.0 kg of liquid oxygen. This is produced from 1,775.7 litres of water electrolysed into 1,578..4 kg of oxygen and 197.3 kg of hydrogen. 493.4 kg of oxygen is surplus. A 200 kW system is required to produce fuel from water in this way, to fill up each tank in 56 hours. Seven tanks require 1.4 MW capability.

The same fuel cell system that drives the electric pumps and electric fans, along with the zero boil off cryogenic system, also has sufficient capacity when plugged into the power mains, to refuel itself with tap water.

25 MW power satellite element may be orbited that masses less than 1,100 kg.. The concentrating photovoltaic system is 176 meters in diameter when deployed on orbit. Energising a ion rocket that has 54 km/sec exhaust velocity produces 925 Newtons. On a 2200 kg payload this produces 0.42 meters per second squared. It takes two hours to propel another 1100 kg payload and the satellite itself to an increase in 3 km/sec - which is sufficient to take it to Mars or the Moon - from LEO. 119 kg of additional propellant is required to bring the vehicle to this speed.

Entering Low Lunar Orbit or Low Mars Orbit - requires in both instances approximately 0.7 km/sec. In the case of Mars this may be reduced further by very high altitude aerobraking. Another 28 kg of propellant is required for this. 56 kg to enter LLO and leave LLO back for Earth. To use the ion engine throughout - to leave Earth orbit, enter Lunar Orbit (or Mars orbit) and leave Lunar Orbit (or Mars orbit) and slow by ion engine back into Low Earth Orbit - requires 281.7 kg of propellant overall. This leaves 818.3 kg payload (1800 lbs) in LLO.

A LOX/LH2 rocket with 4.5 km/sec exhaust speed in vacuum, is capable of imparting a 3.3 km/sec delta vee (enough to land and take off from the Moon, or landing with aerobraking on Mars and taking off for orbit again) using 425.3 kg of propellant - leaving 393 kg of useful load. This is enough for two people!

At a couple million dollars per person, this produces a steady revenue - and up to 362 people per year go to the moon.

At 25 MW - a laser powered system sent to GEO, and the L1, and a laser powered engine that modulated exhaust speed - could increase payloads to the moon. A similar system at Earth Sol L1 and Mars Sol L1 could assist in interplanetary journeys - and lift a system off at Mars. The power satellites could also power equipment that processes local fuels into LOX/LH2.

* * *

A 900 kg telecommunications satellite - with a 200 kg laser/ion reusable kick stage - powered by a power satellite - could be launched and migrate to any desired orbit.

722 such satellites launched in a 5 years would capture the world's telecommunications marketplace today - and earn trillions of dollars per year.

* * *

A 25 MW power station that delivered power to any point on Earth at $0.11 per kWh 24/7 earns $24.1 million per year! With a 30 year life span and 8.5% discount rate, this revenue stream is worth $259 million the day it switches on! With 100 kW receivers, each equipped with 85 kWh power packs, that recharge in less than an hour, every three days or allows each satellite to support 20,800 terrestrial users of this size. This is enough to recharge a Tesla and provide a home with power using a Powerwall.

* * *

A quad rotor that consumes 100 kW at vertical take off and landing and maintains a 485 kph cruise - when powered by a 25 MW power satellite - permits 250 to be flying simultaneously! With a 20% utilisation 1250 units would be supported by each power satellite. 43.9 km/$ at $0.11 per kWh - is energy cost. Far less than the cost of an automobile at current fuel prices.