New smallsat launcher start-up.

On 9/18/2014 9:12 AM, Robert Clark wrote:
SpaceX Alum Goes After Falcon 1 Market With Firefly.
Aerospike revival, advances in composite structures are shaping design
of low-cost smallsat launch vehicle.
Aug 25, 2014 Frank Morring, Jr. | Aviation Week & Space Technology
http://aviationweek.com/space/spacex...market-firefly


Excellent news! As described in the article it will use both lightweight
composite tanks and altitude compensating aerospike nozzles.
This small launcher is to be two stage.

Interesting! But why does the world need another Falcon 1 class vehicle?

Is my memory correct that SpaceX gave up on the Falcon 1 because of a
lack of launch customers for that size payload? The current trend is to
piggyback smaller payloads on larger rockets to utilize their excess
capacity which would otherwise go to waste.

On Saturday, September 20, 2014 1:05:00 AM UTC+12, Vaughn wrote:
On 9/18/2014 9:12 AM, Robert Clark wrote:

SpaceX Alum Goes After Falcon 1 Market With Firefly.

Aerospike revival, advances in composite structures are shaping design

of low-cost smallsat launch vehicle.

Aug 25, 2014 Frank Morring, Jr. | Aviation Week & Space Technology

http://aviationweek.com/space/spacex...market-firefly





Excellent news! As described in the article it will use both lightweight

composite tanks and altitude compensating aerospike nozzles.

This small launcher is to be two stage.



Interesting! But why does the world need another Falcon 1 class vehicle?



Is my memory correct that SpaceX gave up on the Falcon 1 because of a

lack of launch customers for that size payload? The current trend is to

piggyback smaller payloads on larger rockets to utilize their excess

capacity which would otherwise go to waste.


Yet, small launchers are being built:

Like the successful rail operators of the 19th century, the successful space operators of the 20th century will develop their own markets.

James Hill for example helped make the Great Northern Railroad succeed by developing wood and paper markets made from trees harvested in the Pacific Northwest.

Consider the Electron:

http://www.stuff.co.nz/technology/ga...blast-off.html

http://www.rocketlabusa.com/

The development of nanosatellites of great capacity, launched cheaply by smaller rockets is one development arc that's possible.

The Electron places 110 kg into a sun synch 500 km polar orbit for $4.9 million.

140 kg may be placed into a 300 km polar orbit, sun synch as well.

Consider piloted operations.

The Russians were selling rides into Earth orbit for $20 million. At a cost of $4.9 million per launch, and creating a spacesuit capable of sustaining a controlled re-entry, there's an opportunity for profits here!

Even at $12 million per suit, a profit could be made. However, innovators have claimed to reduce costs to $40,000 per suit. The incorporation of MEMS technology for life support and power supply, as well as attitude control, will dramatically change the paradigm here -

http://www.tested.com/science/space/...e-suit-design/

Including mechanical counter pressure technology...

http://www.valuewalk.com/2014/09/new...developed-mit/

An acceleration couch along with shock absorbers, fitted to the satellite stand, carries an astronaut fitted with an advanced space suit that successfully withstands re-entry.

The nose cone is designed very similar to a Douglas X-3 cockpit -

http://31.media.tumblr.com/tumblr_mb...lvyo1_1280.jpg

A single $20 million commitment is sufficient to pay for the development of the suit and the acceleration couch and flight control system. The buyer is launched into sun synch polar orbit and does four orbits over a 10 hour period and returns to the launch centre.

Beyond Earth Orbit

Extending duration to two weeks, in a manner similar to Gemini extending the experience of Apollo, allows us to consider return to the Moon.

Apollo 8

A 140 kg astronaut payload combined with two 140 kg booster payloads each with 128.5 kg of propellant, with 4.2 km/sec exhaust speed, is sufficient to send a person to an Apollo 8 style mission to the moon and return to Earth.. At $4.9 million per launch, and $3.5 million per payload, and $20 million for piloted launch, we have $36.8 million to do an Apollo 8 style mission to the moon - per person.

Apollo 11

Three of those boosters in lunar orbit are sufficient to land a person on the lunar surface and return them to Earth. Each booster in lunar orbit requires three launches at Earth - or 9 launches overall. At 8.4 million per launch this is 75.6 million in addition to the $36.8 million. A total of $112.8 million to send one person to the moon and return them to Earth.

Long Duration Spacesuit
Thermal Protection Space****
Deep Space Cryogenic Booster w/ MEMS rocket array
Automated Rendezvous & Docking in EO and Lunar Orbit
Long Duration Cryogenic Storage in Space & on Lunar Surface


Power Satellite

Sun synchronous polar orbits are interesting. At 500 km altitude is 2 hours 37 minutes 30 seconds. Slightly lower altitude, 300 km slightly shorter period, 2 hours - 30 minutes 40 seconds. Slightly higher payload 140 kg. (309 lbs).

Consider inflatable satellites as a means to develop solar concentrators in space;

Inflatable satellites

Satellite Launch Date (UTC) Mass kg Diam m grams/m2

Echo 1......... 1960-08-12 09:36:00 180.00 30.48 61.7
Explorer 9..... 1961-02-16 13:12:00 36.00 3.66 855.4
Explorer 19.... 1963-12-19 18:43:00 7.70 3.66 183.0
Echo 2......... 1964-01-25 13:55:00 256.00 41.00 48.5
Explorer 24.... 1964-11-21 17:17:00 8.60 3.60 211.2
PAGEOS 1....... 1966-06-24 00:14:00 56.70 30.48 19.4
PasComSat...... 1966-07-14 02:10:02 3.20 9.10 12.3
Explorer 39.... 1968-08-08 20:12:00 9.40 3.60 230.9
Mylar Balloon.. 1971-08-07 00:11:00 0.80 2.13 56.1
QiQiu Weixing 1 1990-09-03 00:53:00 4.00 3.00 141.5
QiQiu Weixing 2 1990-09-03 00:53:00 4.00 2.50 203.7

The Echo 1 and Echo 2 satellites are interesting because we know they used the same inflating mechanisms and satellite delivery systems. We know this massed 86.1 kg. This tells us that the inflatable portion massed 32.2 grams per square meter. PasComSat massed only 12.3 grams per square meter.

With MEMs and GBO technologies,

http://en.wikipedia.org/wiki/Miniaturized_satellite
http://www.sciencemag.org/content/28.../2451.abstract

we know that very advanced solar concentrators could be considered that mass around 6 grams per square meter. Thus a 140 kg payload can orbit a 211.1 meter diameter system. At 55% efficiency, a small satellite in a sunset/sunrise orbit can deliver 26.2 MW to any point on Earth.

From 1 hour before sunset to 1 hour after sunset, and from 1 hour before sunrise, to 1 hour after sunrise, the satellite will be in the sky for 14 minutes 40 seconds, for every spot on Earth!

So a receiver collecting energy at 26.2 MW rate for 14 minutes 40 seconds, can expend energy at 523,200 Watts over 12 hours.


Battery Cost Wh/kg J/kg Wh/l Tonnes cubic m meters $

Lead-ac $0.17 41 146000 100 153.13 62.78 3.975 $1,067,328
Alkalin $0.19 110 400000 320 57.08 19.62 2.697 $1,192,896
Carbon- $0.31 36 130000 92 174.40 68.24 4.087 $1,946,304
NiMH $0.99 95 340000 300 66.09 20.93 2.756 $6,215,616
NiCad $1.50 39 140000 140 160.98 44.85 3.553 $9,417,600
Lithium $0.47 128 460000 230 49.05 27.30 3.011 $2,950,848


Fifty ground stations per satellite may be supported in this way. At $0.11 per kWh - fifty 523.2 kW ground stations generate $25.22 million/year. With a 20 year life span a single satellite produces $504.50 million. Discounted at 8% per year the satellite's revenue may be sold for $247.61 million the day its starts generating power.

Bandgap matched laser energy is efficiently converted to DC power at rates of 7.3 kW/cm2. Thus a 350 mm diameter wafer receiver is sufficient to collect the laser energy beamed to Earth to recharge the battery packs in 14 minutes every 12 hours, and then operate 12 hours between charging. The system operates during charging as well.

The launch is $4.9 million. At $25,000 per kg and 140 kg the satellite costs $3.5 million. Each ground station costs $1.5 million, which paid in addition to the power.

$1.5 million ground station + $0.11 per kWh * 4.586 million kWh/year
$1.5 million deposit + $0.50446 million per year x 20 years
$10.089 million commitment per ground station
$504.5 million per satellite -- $247.61 million

Satellite cost: $7.5 million -- $150,000 per ground station.

Ten ground stations and the first satellite costs $37.5 million. Each additional satellite costs $7.5 million.

Remote microgrids target niche markets, such as mines and other commodity extraction facilities not connected to an existing grid, physical islands, rural villages in the developing world, and mobile and tactical applications for military agencies.

These remote power systems number in the thousands, many are still powered by diesel generation.

Today, an increasing number of remote microgrids showcase smart and much cleaner combustion technologies capable of reducing diesel consumption by as much as one-third, even without any renewable generation.

The total worldwide capacity of remote microgrids will grow from 286 megawatts (MW) in 2013 to nearly 980 MW in 2020.

Under a more aggressive scenario, total capacity will reach 1,071 MW in 2020.

https://www.youtube.com/watch?v=_MKYFI7BPBo
https://www.youtube.com/watch?v=-Nm16wp0kMs

26.2 MW of laser energy - produces 5695.6 Newtons with 9.2 km/sec exhaust speed

Laser Propelled Rockets:

Power = 1/2 * mdot * Ve^2

Ve = 9200 m/sec
Power = 26.2 MW

means

mdot = 2 * Power/Ve^2 = 0.619 kg/sec

So

Force = mdot * Ve = 0.619 * 9200 = 5695.6 Newtwons

5695.6 / 9.80655 = 580.8 kgf

580.8 / 1.28 = 453.75 kg - TAKE OFF WEIGHT

u = 1 - 1/exp(9.2/9.2) = 0.63212

propellant = 286.83

payload + inert = 166.92


If half the velocity - up to 4.6 km/sec is drawn from the atmosphere - and 4.6 km/sec is in the form of stored propellant, payloads increase.


u = 1 - 1/exp(4.6/9.2) = 0.39347

propellant = 178.54

payload + inert = 275.21 kg (606.56 lbs)


Further, by reducing the exhaust speed to 4.6 km/sec mass flow rate increases to 2.476 kg/sec for a power limited system, and that increases thrust to 11,391.3 Newtons. That's 1,161.6 kg.

At 1.28 gees at lift off, we have an increased take off weight of 907.5 kg take off weight.

With 573.65 kg of inert propellant, and using atmosphere as inert propellant below 4.6 km/sec, we can lift 333.85 kg (735.8 lbs) into LEO in a single stage craft that operates at 26.2 MW power level in this way.

This is larger than the 140 kg delivered by the Electron launcher. In fact, it more than double the size! So, since area scales with size, so too does power and with that, lift of a laser powered rocket.

This unleashes a Moore's law (some have said Mook's law) of laser propulsion expansion of capabilities!

Chemical TSTO Launcher
140.00 kg -- 26.2 MW 222.1 m

Laser SSTO Launcher

907.5 kg 573.65 kg 333.85 kg -- 52.4 MW 314.1 m
1,815.0 kg 1,147.30 kg 667.70 kg -- 104.8 MW 444.2 m
3,630.0 kg 2,294.60 kg 1,335.40 kg -- 209.6 MW 628.2 m
7,260.0 kg 4,389.20 kg 2,670.80 kg -- 519.8 MW 888.4 m
14,520.0 kg 8,778.40 kg 5.341.60 kg -- 1,039.6 MW 1,256.4 m

etc.

A flight from the Earth to the Moon and back, from orbit, requires a delta vee of 2.95 + 4.60 = 7.55 km/sec. With an exhaust speed of 15.10 km/sec we have a propellant fraction of 0.39347 with the following propellant expenditures;

1.00000 1.00000 - LEO
0.82253 0.17747 - LEO -- LFR
0.70632 0.11621 - LFR -- Lunar Surface
0.60653 0.09979 - Lunar Surface -- Earth Return

Delivering the following

LEO Luna and Back

333.85 kg -- 202.49 kg
667.70 kg -- 404.98 kg
1,335.40 kg -- 809.96 kg
2,670.80 kg -- 1,619.92 kg

etc...

With Solar power satellites at Earth-Moon Lagrange Point 1, Lagrange Point 2, Lagrange Point 4 & 5 - and a receiver on the moon, to assist with landings and take offs.

https://www.youtube.com/watch?v=XzeCQblYHic
https://www.youtube.com/watch?v=P8Pb_psj1A8
https://www.youtube.com/watch?v=WGPBsLLAHU8
https://www.youtube.com/watch?v=oD8TfjDMYT0

The Sikorsky Firefly is interesting. At 1100 lbs (500 kg) the Li-ion batteries contain 64 kWh of electricity. At 140 kW this is enough for 24.7 minutes of flight. Since its impossible to discharge batteries 100% - this accounts for the 16 minutes of flight.

A hydrogen fuel cell that broke down water into hydrogen and oxygen, and stored it on board the aircraft, to make water (also stored) again to produce power - and allocating 250 kg for the propellant storage and 250 kg for the associated hardware, we have 17.1x the energy stored on board as the electric battery system. That is 422.4 minutes. (about 7 hours) At 159 km/hr cruise speed this is a range of 1,119.4 km between charges!

140 kW Proton Exchange Membrane fuel cell, at $63 per kW costs $8820. This is 1/3 the cost of a Lycoming 360 engine it replaces! A 140 KW brushless DC motor combined with a solid state controller costs $2200 - so overall, the system is half the cost of the Lycoming.

The system requires 235 kW of laser energy to charge at the same rate it discharges. Quadrupling the size of the Proton Exchange Membrane system, allows it to charge in one quarter the time it flies. 500 litres of water are converted to a full charge of hydrogen and oxygen in 1 hour and 45 minutes of beam time.

The ability to receive power in flight permits reception of power during the two hours surrounding either sunrise or sunset. The aircraft is then capable of flying 7 hours after spending 1.75 hours charging.

Automated electric helicopters that are charged with a power beaming set up provides flight on demand.

https://www.youtube.com/watch?v=KzWwGvAalRk
https://www.youtube.com/watch?v=undX_rxY-dQ
https://www.youtube.com/watch?v=NevgqMqWf5Y

A total of 111 of the C300 helicopters are supported per satellite, which provide 14 hours of flight service out of every 24 hours. At $0.11 per kWh the power costs are $215 per day per vehicle. That's $15.35 per hour - or 9.65 cents per km.

At $250,000 and an 8% discount rate, with a 20 year life span, and 4% maintenance cost, we have $35,463 per year. Dividing by 5113.5 hours per year obtains $6.94 per hour. That's another 4.35 cents per km. A total of $0.14 per km. Dividing by three people, that's less than $0.05 per passenger km..

The MD-500 helicopter has a 207 kW engine, a 48% increase in power, and lifts 100% increase in weight! 76 of these ships can be supported per satellite. Greater lift capacity combined with higher engine cost, means this five passenger system, is charged in two hours (even in flight) and operates 10 hours nonstop. This permits 24 hours of flight every 24 hours. So, this system is always on the go!

Crew: 1-2
Capacity: 5 total
Length: 30 ft 10 in (9.4 m)
Rotor diameter: 26 ft 4 in (8.03 m)
Height: 8 ft 2 in (2.48 m)
Empty weight: 1,088 lb (493 kg)
Max. takeoff weight: 2,250 lb (1,157 kg)
Powerplant: 1 × Allison 250-C20 Turboshaft, 278 hp (207 kW)

Performance

Maximum speed: 152 knots (175 mph, 282 km/h)
Cruise speed: 125 kn (144 mph, 232 km/h)
Range: 375 mi (605 km)
Service ceiling: 16,000 ft (4,875 m)
Rate of climb: 1,700 ft/min (8.6 m/s)

A speed of 282 km/h x 24 hours = 6768 km/day. That's 2,472,012 km per year - and with five passengers - that's 12,360,060 passenger-km per year. With a 20% service cycle time - this translates to 9,888,048 passenger-km per vehicle per year - with 95 ships per satellite.

The cost of power at $0.11 per kWh is $22.77 per hour. This is $4.56 per passenger. At 282 km/hr this is 1.62 cents per passenger-km!!

The MD-520N costs $1.3 million used. The MD-6M Little Bird is $3.6 million.. The Allison 250 C engine is $200,000+. That's enough to buy 3 MW of Proton Exchange Membranes - and at 207 kW use rate, you can have as much as 6:1 advantage during high speed charge. With a $3.6 million price tag and 80% utilization rate, and a 4% maintenance cost we have $144,000 per year in maintenance, spread over 7,020.8 hours. That's $20.51 per hour. Financing $3.6 million over 20 years at 8% costs $366,667 per hour. Dividing across 7,020.8 hours that's $52.23 per hour. A total cost of $95.51 per hour. Dividing by five passengers that's $19.10 per passenger hour. Dividing by 282 km/hr that's 6.77 per passenger km.

Charging $1.50 for the first 5 km and $0.15 per km thereafter, (with distance calculated by straight line from point of pick up to point of departure, with total paid upon entry, so no extra charges are incurred for pick up and drop off of other passengers) a system of electric helicopter drones would already be competitive with any other system of transport.

With five hours at either end - to get to and from airports - combined with cancellations and other factors - we can beat any travel of any sort in terms of price, quality and speed of service with any distance of less than 1,410 km for $211.50. This is the distance from Rome to Paris. It costs 315..92 euro by car ($405.36) in fuel and takes 14 hours. A point to point electric drone heli at these prices, makes a lot of sense!

http://www.flightstats.com/go/Media/stats.do

Paris to New York would take 20.7 hours point to point - and cost $875 each way. Not bad.

Boeing has a Quad Tilt Rotor
http://i799.photobucket.com/albums/y...pire/hvtol.jpg

Which ups the ante - by converting to an airplane type configuration - giving a much higher speed and better efficiency than a pure helicopter.

Quad Rotors have a long history
http://illumin.usc.edu/assets/media/...5a2bc282_o.jpg

And a brilliant future
http://realitypod.com//HLIC/8e62034e...bd278eb44d.jpg

We should be able to cut the costs to about 1/10th the costs calculated here, for the hardware, and cut the costs of the energy by about half in the short term, while increasing speeds to 1,000 kph - typical of airliners today. This radically reduces cost per passenger km (or tonne km for cargo).

Hoverbike
https://www.youtube.com/watch?v=mNkLjv--q7Y

E-Fan
https://www.youtube.com/watch?v=HTNR9O4PmNo

In article ,
"Robert Clark" wrote:

Richard Branson has claimed to be a proponent of governmental initiatives
aimed at reducing CO2 emissions. If so he should try to convert his entire
Virgin Atlantic fleet to electric or hydrogen powered.

How efficient could such jet aircraft be compared to kerosene fueled jets?

Bob Clark

Not very!

1. Electric jets are a non-starter, since electricity storage defeats it
because of weight.

2. Even liquid hydrogen has such poor energy density that storage tanks
would occupy the entire passenger cabin -- and then some.

Sorry, but hydrocarbons present, by far, the best bets for fuel.

On Monday, September 22, 2014 6:37:40 AM UTC+12, Orval Fairbairn wrote:
In article ,

"Robert Clark" wrote:



Richard Branson has claimed to be a proponent of governmental initiatives

aimed at reducing CO2 emissions. If so he should try to convert his entire

Virgin Atlantic fleet to electric or hydrogen powered.



How efficient could such jet aircraft be compared to kerosene fueled jets?



Bob Clark



Not very!



1. Electric jets are a non-starter, since electricity storage defeats it

because of weight.



2. Even liquid hydrogen has such poor energy density that storage tanks

would occupy the entire passenger cabin -- and then some.



Sorry, but hydrocarbons present, by far, the best bets for fuel.

Thermal efficiency of a Lycoming O-300 produces 300 HP while consuming 15.6 gallons of fuel per hour.

http://www.lycoming.com/Portals/0/te...Operations.pdf

15.6 gallons of fuel contain 2.218 GJ so per hour that's a power level of 616.2 MW. Now 300 HP is 223.7 MW. This is a thermal efficiency of

223.7 / 616.2 = 36.3%

Now that we know the figure of merit for the engine, lets look at the fuel;

15.6 gallons weigh 48.06 kg and occupies 59.06 litres of volume.

So, Jet fuel contains 46.16 MJ/kg of weight and 37.56 MJ/litre of volume.

Alright, so let's consider a Proton Exchange Membrane or a Solid Oxide fuel cell the combines hydrogen with atmospheric oxygen to produce DC electricity.

http://www.hydrogen.energy.gov/pdfs/..._factsheet.pdf

http://www1.eere.energy.gov/hydrogen..._factsheet.pdf

So, efficiencies of 60% are achieved routinely today in a variety of fuel cells that combine hydrogen with oxygen in the air.

A kg of hydrogen contains 141.3 MJ of energy and the fuel cell converts it to mechanical power with nearly twice the efficiency of an internal combustion engine.

Using an absorption refrigeration cycle to cool and liquefy the hydrogen gas, and provide cabin air, this efficiency can be brought even higher!

http://en.wikipedia.org/wiki/Absorption_refrigerator

So, let's consider a direct replacement of a Lycoming O-360 with a DC electric motor with a 270 kW peak output - as here.

https://www.youtube.com/watch?v=oD8TfjDMYT0

But in a Cessna 172 - which uses the same engine. It carries 172 kg of av-fuel, so if it were equipped to carry 172 kg of liquid hydrogen to feed a 270 kW fuel cell that powered a 270 kW DC electric motor - the same size as the one in the Sikorsky Firefly shown above -


171 kg av-fuel
6421.9 MJ heat energy
36.3% efficiency
2331.2 MJ mechanical energy

1289 km range
226 km/hr - speed
5.70 hours + 0.75 hours reserve =6.45 hours flight time


171 kg - hydrogen
24,162.3 MJ heat energy
60.0% efficiency
14,497.4 MJ mechanical energy
6.219x
40.11 hours - 0.75 hours reserve = 39.36 hours
226 km/hr
8,895.7 km range + 45 minute reserve.

Now, the BMW Hydrogen 7 vehicle has a liquid hydrogen fuel tank that contains nearly 170 litre(45 gallon), bi-layered and highly insulated tank that stores the fuel as liquid rather than as compressed gas, which BMW says offers 75% more energy per volume as a liquid than compressed gas at 700 bars of pressure.

The hydrogen tank's insulation is under high vacuum in order to keep heat transfer to the hydrogen to a bare minimum, and is purportedly equivalent to a 17-metre (56 ft) thick wall of polystyrene Styrofoam.

To stay a liquid, hydrogen must be super-cooled and maintained at cryogenic temperatures of, at warmest, -253 °C (-423.4 °F). When not using fuel, the Hydrogen 7's hydrogen tank used to warm and the hydrogen started to vaporize. Once the tank's internal pressure reaches 87 psi, at roughly 17 hours of non-use, the tank used to safely vent the building pressure. Over 10-12 days, it used to completely lose the contents of the tank because of this.

The use of MEMS cryocoolers and MEMS based fuel cells, have solved this problem, using a portion of the hydrogen to run cryocoolers that are helped along with absorption refrigeration, to make use of 90% of the energy in the hydrogen to keep the balance of the hydrogen very cool indeed!

http://www.hydrogencarsnow.com/hydrogen-fuel-tanks.htm

This not only gets rid of any explosion hazard, since the system vents water, it also extends the life of hydrogen in your tank to exceed that of av fuel in your tank!

http://www.exxonmobilaviation.com/av...gguide2003.pdf

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...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. Furthermore, the volume of the engine nacelle, remains unchanged, and can be equipped with a hydrogen tank to maintain the same pitch moments!

http://www.aerotrek.aero/photos/tech/dimensions.gif

Thus, the payload of the vehicle, may be increased as well as the range (and speed).

Which is pretty awesome!

I have written elsewhere about a 26 MW power satellite that beams energy down to ground stations 15 minutes every 12 hours. At 60% conversion efficiency, this is 14.04 GJ. Enough to produce 99 kg of hydrogen every 12 hours. 198 kg of hydrogen 1782 litres of water - every 24 hours. Of course, 171 kg is enough to power a Cessna 172 for 40.11 hours. 198 kg is enough to power a Cessna 172 for 46.44 hours! A Cessna 172 that has a 2000 hour overhaul every 15 months flies 1600 hours per year. So, over a 24 hour period it consumes 18.68 kg of hydrogen. With 198 kg per ground receiver every24 hours 10.6 aircraft may be supported.

Now, 26 MM satellite in a sun-synch polar orbit support 50 ground stations of the type described above. This means that 530 Cessna 172s converted to 'burn' hydrogen in a fuel cell using an electric motor with the superlative range outlined, are supported by each satellite.

Now 43,000 Cessna 172s have been built and about half of them are still flying. That's 21,500 - dividing by 530 that obtains 41 satellites of the type described. Fewer than 1,000 piston aircraft are shipped each year today. So, the purchase of 530 aircraft fuelled at 50 hydrogen stations spread evenly across the globe, easily reached by aircraft that have 8,895 km range!

Evenly spread across the land, each of the 50 terrestrial stations are 980 km from each other. So, this is a very interesting business model!

Although, I like drone like ease of use, combined with VTOL/STOL operation - of an autogyro - or powered autogyro like the Fairey Rotodyne...

http://spirit.eaa.org/news/2013/imag...valon-gyro.jpg

http://terpconnect.umd.edu/~leishman...s/rotodyne.gif

Of course two auto-gyro blades spinning in opposite directions, provide for higher speeds

http://cutangus.deviantart.com/art/A...7-02-269696910

But, a hydrogen fuel/cell Cessna 172 has a lot to recommend it at the outset!

http://www.rocketlabusa.com/

The Electron is an interesting rocket.

It has 120 kN thrust at lift off. It masses 9560 kg. The first stage masses 764 kg inert mass and carries 6992 kg of propellants. The second stage masses 144 kg inert mass and carries 1319 kg of propellants. The third stage masses 200 kg and carries 180 kg of propellants. The payload is 140 kg carried into a Sun Synch polar orbit 280 km altitude.

Now the BD-5B aircraft with a Subaru EA-83 engine masses 167 kg - with 85 kg being the engine!! 82 kg is the aircraft!

The only reason I mention this is because a person in a biosuit attached to a foam acceleration couch custom tailored for them - with an airframe around them - would not be very massive. Life Support systems and power systems - MEMS based - like the MEMS based cryocoolers and fuel cells mentioned previously - make very lightweight systems possible!

So a BD-5 sized Dynasoar atop an Electron rocket - should be possible! Especially if it incorporates the third stage kick rocket - to help with deorbit after 8 orbits (in 12 hours).

http://www.astronautix.com/craft/dynasoar.htm

http://gizmodo.com/mits-new-biosuit-...-to-1636382746

http://ntrs.nasa.gov/archive/nasa/ca...0120009158.pdf




This type of vehicle would be available to the adventurous for $10 million - and you'd get to keep the Spacecraft and Spacesuit after!

In article ,
William Mook wrote:

On Monday, September 22, 2014 6:37:40 AM UTC+12, Orval Fairbairn wrote:
In article ,

"Robert Clark" wrote:



Richard Branson has claimed to be a proponent of governmental initiatives

aimed at reducing CO2 emissions. If so he should try to convert his
entire

Virgin Atlantic fleet to electric or hydrogen powered.



How efficient could such jet aircraft be compared to kerosene fueled
jets?



Bob Clark



Not very!



1. Electric jets are a non-starter, since electricity storage defeats it

because of weight.



2. Even liquid hydrogen has such poor energy density that storage tanks

would occupy the entire passenger cabin -- and then some.



Sorry, but hydrocarbons present, by far, the best bets for fuel.

Thermal efficiency of a Lycoming O-300 produces 300 HP while consuming 15.6
gallons of fuel per hour.

http://www.lycoming.com/Portals/0/te...20Operations.p
df

15.6 gallons of fuel contain 2.218 GJ so per hour that's a power level of
616.2 MW. Now 300 HP is 223.7 MW. This is a thermal efficiency of

223.7 / 616.2 = 36.3%

Now that we know the figure of merit for the engine, lets look at the fuel;

15.6 gallons weigh 48.06 kg and occupies 59.06 litres of volume.

So, Jet fuel contains 46.16 MJ/kg of weight and 37.56 MJ/litre of volume.

Alright, so let's consider a Proton Exchange Membrane or a Solid Oxide fuel
cell the combines hydrogen with atmospheric oxygen to produce DC electricity.


http://www.hydrogen.energy.gov/pdfs/..._factsheet.pdf

http://www1.eere.energy.gov/hydrogen...lcell_factshee
t.pdf

So, efficiencies of 60% are achieved routinely today in a variety of fuel
cells that combine hydrogen with oxygen in the air.

A kg of hydrogen contains 141.3 MJ of energy and the fuel cell converts it to
mechanical power with nearly twice the efficiency of an internal combustion
engine.

Using an absorption refrigeration cycle to cool and liquefy the hydrogen gas,
and provide cabin air, this efficiency can be brought even higher!

http://en.wikipedia.org/wiki/Absorption_refrigerator

So, let's consider a direct replacement of a Lycoming O-360 with a DC
electric motor with a 270 kW peak output - as here.

https://www.youtube.com/watch?v=oD8TfjDMYT0

But in a Cessna 172 - which uses the same engine. It carries 172 kg of
av-fuel, so if it were equipped to carry 172 kg of liquid hydrogen to feed a
270 kW fuel cell that powered a 270 kW DC electric motor - the same size as
the one in the Sikorsky Firefly shown above -


171 kg av-fuel
6421.9 MJ heat energy
36.3% efficiency
2331.2 MJ mechanical energy

1289 km range
226 km/hr - speed
5.70 hours + 0.75 hours reserve =6.45 hours flight time


171 kg - hydrogen
24,162.3 MJ heat energy
60.0% efficiency
14,497.4 MJ mechanical energy
6.219x
40.11 hours - 0.75 hours reserve = 39.36 hours
226 km/hr
8,895.7 km range + 45 minute reserve.

Now, the BMW Hydrogen 7 vehicle has a liquid hydrogen fuel tank that contains
nearly 170 litre(45 gallon), bi-layered and highly insulated tank that stores
the fuel as liquid rather than as compressed gas, which BMW says offers 75%
more energy per volume as a liquid than compressed gas at 700 bars of
pressure.

The hydrogen tank's insulation is under high vacuum in order to keep heat
transfer to the hydrogen to a bare minimum, and is purportedly equivalent to
a 17-metre (56 ft) thick wall of polystyrene Styrofoam.

To stay a liquid, hydrogen must be super-cooled and maintained at cryogenic
temperatures of, at warmest, -253 °C (-423.4 °F). When not using fuel, the
Hydrogen 7's hydrogen tank used to warm and the hydrogen started to vaporize.
Once the tank's internal pressure reaches 87 psi, at roughly 17 hours of
non-use, the tank used to safely vent the building pressure. Over 10-12 days,
it used to completely lose the contents of the tank because of this.

The use of MEMS cryocoolers and MEMS based fuel cells, have solved this
problem, using a portion of the hydrogen to run cryocoolers that are helped
along with absorption refrigeration, to make use of 90% of the energy in the
hydrogen to keep the balance of the hydrogen very cool indeed!

http://www.hydrogencarsnow.com/hydrogen-fuel-tanks.htm

This not only gets rid of any explosion hazard, since the system vents water,
it also extends the life of hydrogen in your tank to exceed that of av fuel
in your tank!

http://www.exxonmobilaviation.com/av...gguide2003.pdf

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.
Furthermore, the volume of the engine nacelle, remains unchanged, and can be
equipped with a hydrogen tank to maintain the same pitch moments!

http://www.aerotrek.aero/photos/tech/dimensions.gif

Thus, the payload of the vehicle, may be increased as well as the range (and
speed).

Which is pretty awesome!

I have written elsewhere about a 26 MW power satellite that beams energy down
to ground stations 15 minutes every 12 hours. At 60% conversion efficiency,
this is 14.04 GJ. Enough to produce 99 kg of hydrogen every 12 hours. 198
kg of hydrogen 1782 litres of water - every 24 hours. Of course, 171 kg is
enough to power a Cessna 172 for 40.11 hours. 198 kg is enough to power a
Cessna 172 for 46.44 hours! A Cessna 172 that has a 2000 hour overhaul
every 15 months flies 1600 hours per year. So, over a 24 hour period it
consumes 18.68 kg of hydrogen. With 198 kg per ground receiver every24 hours
10.6 aircraft may be supported.

Now, 26 MM satellite in a sun-synch polar orbit support 50 ground stations of
the type described above. This means that 530 Cessna 172s converted to
'burn' hydrogen in a fuel cell using an electric motor with the superlative
range outlined, are supported by each satellite.

Now 43,000 Cessna 172s have been built and about half of them are still
flying. That's 21,500 - dividing by 530 that obtains 41 satellites of the
type described. Fewer than 1,000 piston aircraft are shipped each year
today. So, the purchase of 530 aircraft fuelled at 50 hydrogen stations
spread evenly across the globe, easily reached by aircraft that have 8,895 km
range!

Evenly spread across the land, each of the 50 terrestrial stations are 980 km
from each other. So, this is a very interesting business model!

Although, I like drone like ease of use, combined with VTOL/STOL operation -
of an autogyro - or powered autogyro like the Fairey Rotodyne...

http://spirit.eaa.org/news/2013/imag...valon-gyro.jpg

http://terpconnect.umd.edu/~leishman...s/rotodyne.gif

Of course two auto-gyro blades spinning in opposite directions, provide for
higher speeds

http://cutangus.deviantart.com/art/A...7-02-269696910

But, a hydrogen fuel/cell Cessna 172 has a lot to recommend it at the outset!

Overlooked is the size of the tankage required to pack the LH2. As I
posted earlier, just the tanks would occupy the useful part of the
aircraft. Also, Branson is talking about airliners, not C172s.

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.

As noted in my comment, and ignored by you, these reductions in weight mean that hydrogen fuelled systems have more power per weight, empty, and have 3x the range of their hydrocarbon counterparts.

http://www.gizmag.com/boeing-phantom...-flight/26432/
https://www.youtube.com/watch?v=XzeCQblYHic
https://www.youtube.com/watch?v=uBrSi4W3KHM

Also, Branson is talking about airliners, not C172s.

So? The technology works with any airframe size. So, why not start with less expensive small airframes and move to larger airframes?

That's what Airbus has done
https://www.youtube.com/watch?v=l_vOVOTglt4

They've even proven a concept studied by engine manufacturers, namely electric high bypass turbofans!

https://www.youtube.com/watch?v=w5t8VdLpsOA

Here's more on this concept - using hydrogen as a direct replacement ...

https://www.youtube.com/watch?v=Z6rsMyyQnBA
https://www.youtube.com/watch?v=izAEgD99q-s
https://www.youtube.com/watch?v=C0fcpIT2M08

Of course, using fuel cells with electric drive turbofans doubles thermal efficiencies and combined with the light weight of hydrogen, extends ranges dramatically whilst improving payload fractions!

The A320 Neo uses advanced aerodynamics and very high bypass ratio engines - is a step in this direction!

http://www.airbus.com/aircraftfamili...ht-on-a320neo/

The A320 carries at most 24,545 kg of Jet fuel. The energy equivalent amount of hydrogen is 7,990 kg of liquid hydrogen.

Using fuel cells to make electricity to drive an electric turbofan as shown in the videos above, reduces this amount by half to 3,995 kg. Total volume 57,072 litres. Subtracting off the 30,190 litres already allocated for kerosene obtains a difference of 19,882 litres. A pair of cylindrical tanks in the cargo hold below the main deck each 580 mm in diameter reduce the cargo volume by 25% with no changes to the airframe, yet increase the payload by 20,550 kg. The mass of the tanks are less than 800 kg.

With slight changes to the airframe, increasing the diameter from a 3.95 x 4.14 meter oval to 4.00 x 4.20 meter oval - and increasing length from 35.57 m to 36.02 m - increases cargo volume, increases cabin size - increasing from 185 passengers to 225 passengers while carrying 7,990 kg of hydrogen which doubles range while reducing noise reducing maintenance reducing take off length, increasing operating altitude and speed and ending any pollutants whatever! (range goes from 6,100 km to 12,200 km!)

Now at 900 km/hr it takes 13.55 hrs to travel 12,200 km. With a 0.75 hr reserve that's 12.8 hours to recharge 7,990 kg of hydrogen.

At 70% electrolyzer efficiency, this requires 1.62 TJ of received energy. This is 35.12 MW.

http://www.eurocontrol.int/sites/def...risis-2011.pdf

With each airframe utilized 65% of the time the average power required per aircraft is 22.8 MW. 10 aircraft per eight satellites. So, 40 satellites support 50 aircraft.

$2.687 per gallon Jet fuel. That's $0.71 per litre. $17,427 per flight. That's $1,361.50 per hour. With 65% utilization, that's $885 per hour.

Translating this cash flow to what my costs have to be for beamed power from space, at 22.8 MW average power level, that's 3.88 cents per kWh.

At $0.11 per kWh, which is my base price for power delivered anywhere, we have to charge $49,406 per flight. For 225 persons this is $220 each - and dividing by 12,200 km we have $18 per passenger per 1000 km.