Using waste for propulsion ?

On Sunday, October 30, 2016 at 5:13:59 PM UTC+13, Greg (Strider) Moore wrote:
"JF Mezei" wrote in message
web.com...

Just saw a picture of NASA testing the shuttle SSMEs with perfectly blue
flame coming out.

Those engines dump perfectly good water overboard. Since water is "life"
on a long duration ship, is that the best use of it ?

Probably.
Start by looking at the size of the ET and now calculate how much the
astronauts would have to breath out and pee out to make that much water.



So far, discussions have been on closed loop ECLSS where you try to
recycle everything.

What if we went about it differently ?

Produce methane from waste, and not only burn it for propulsion, but
instead use it to accelerate waste mass as well ? (think canon where you
accelerate waste mass out).

Canon? Canon where? I think you mean cannon or in other words, a reaction
mass engine.. i.e... a ROCKET...



This would avoid the need to require "closed loop" to work. You'd end up
having to load more food/water but less mass dedidated to propulsion.

Yes, you'd have to load a LOT more water (since we're not reclaiming food,
that doesn't really change much).

But taking a WAG, the astronauts aren't going to breath/pee an ET worth of
water.
(yes, I know you don't really mean adding something that size to say a Mars
craft.)

But think of it this way. You're either bringing up water to drink and then
pee and then power the rocket, OR... water to drink/pee/recycle and H2 and
O2 to power the rocket. i.e. you still need roughly the same amount of fuel
in either case, it doesn't really matter where you get it from.


Could solar panels power hydolysis for waste water to extract H2 and O2
which could then be burned ?

Consider a concept of an expedition ship which orbits mars while crews
go down and back up to it. That ship would collect waste water during
the trip to mars, and use the sun to slowly convert it to H2 and O2 with
hydrolisys while the crew are on mars and ship is iddle. When crews come
back, there is enough H2 and O2 produced to get the ship out of mars
orbit and head towards earth.

Why bother collect waste water? Really the only thing you're getting is H2,
since you can get O2 itself from the atmosphere.




Could this work, or is the propulsion potential from waste not even in
the right order of magniture to be worth looking at ? (for a whip with
say 100 pax).

I'm pretty sure it's not even close to the right magnitude.


--
Greg D. Moore http://greenmountainsoftware.wordpress.com/
CEO QuiCR: Quick, Crowdsourced Responses. http://www.quicr.net


An adult male according to NASA scientist Harry Jebens who complied this information consumes 3.65 kg/day and excretes the same amount. The External Tank carries 740,000 kg of propellant. So, on an equal mass basis understanding that LOX/LH2 propellant is less dense than food and water, urine and feces, we have 202,739 man days of material. That's 555 man years of material. For a crew of 7 that's 79 years of material.

So, this scales the size of things.

Since LOX/LH2 can be combined in a fuel cell to make electricity and potable water, and LOX can be breathed, its far more likely fuels are used as raw materials in life support. Especially cryogenic fuels that tend to boil off from their storage tanks.

A Cessna Citation has an empty weight of 9.8 tonnes and carries 6.6 tonnes of payload and fuel. A total of 16.4 tonnes.

WIth a crew of 2 and 12 passengers, operators assume a weight of 74 kg per passenger with a 11 kg luggage weight. A total of 85 kg per passenger. That's a total of 1.2 tonnes. This leaves 5.4 tonnes of consumables.

Using this as a model whilst realising wings present on the Citation X would be replaced with thermal protection system, and jet engines replaced with rocket engines, and so forth, this 5.4 tonnes or 5400 kg permit the storage at 3.65 kg per day of 1479 man-days. With 14 people on board, this is a little over 105 days per person!

Now, 0.686 kg per day is oxygen, and 2.4 litres per day is water, either through direct consumption, or rehydrating food.

We also have to scrub 0.857 kg per day of CO2 out of the air and odors.

Given the solid contents of dehydrated foods, 882 kg of food concentrates supply 14 people for 105 days.

As for air, we use the same process used aboard the ISS. This uses hydrogen to absorb CO2 using the Sabatier reaction.

Sabatier

CO2 + 4 H2 -- CH4 + 2 H2O

So, 0.857 kg per day per passenger, or 12 kg per day for 14 passengers, of CO2 requires 2.18 kg of hydrogen gas be used in this way. This produces 4.36 kg of methane and 9.82 litres of water.

The byproducts are futher processed to recovery the consumables and make useful products like carbon black;

Pyrolysis

CH4 + energy --- C + 2 H2

Electrolysis

2 H2O + energy --- O2 + 2 H2

The methane is pyrolysed efficiently with microwaves, to produce elemental carbon which is used for odour control, and hydrogen, which is reused in the Sabatier reactor. The water is collected and electrolytically reduced to form oxygen and hydrogen again. The hydrogen is reused, and the oxygen is re-breathed.

Now, 4.36 kg of methane breakd down into 1.09 kg of hydrogen and 3.27 kg of carbon black. 9.82 litres of water break down into 1.09 kg of hydrogen and 8.73 kg of oxygen. This restores the hydrogen and oxygen required for the crew. This requires 177.7 megajoules per day. That's 2,056 Watts of power!

So, on the first order, this requires ZERO mass consumption.

A concentrating solar panel that uses thin film concentrators in conjunction with high efficiency photovoltaics, requires only 100 grams of hardware to generate this amount of power reliably at 1 AU.

A rechargeable Lithium-Ion battery of the type used in the Tesla motorcar, stores 11.6 kWh/kg. So a collection of primary CPV power source consisting of four concentrators each 1.8 meter diameter inflatable concentrator focused on to a 90 mm diameter CPV unit, each produces 2.1 kW each massing 0.25 kg. all driving a 2 kg battery, with another 1 kg of associated control hardware (4 kg overall) provides 23.2 kWh of energy storage - sufficient to drive the system just described for 11.5 hours of darkness - and indefinitely in sunlight! A six kg system can provide 23 hours of life support when the CPV units are in the dark.

https://www.google.com/patents/US20050051205

So, this is the air taken care of.

The water, is something else.

Here we have a wide of wastes, waste water, urine, feces, packaging, waste paper, etc.

These are all dehydrated at room temperature and low pressure, with recovery of the water vapor at low temperature, and higher pressure.

The water vapor is perfectly pure, and used to hydrate the stored food concentrates.

The mixed waste solids left behind after dehydration are exposed to UV light, then oxidised using hydrogen peroxide and ozone in an integrated processing unit.

The unit produces CO2, H2O, and ash. The CO2 is processed as with the air, into elemental carbon as described above, and oxygen, and the water is processed into hydrogen and oxygen, to process the CO2. This results in

Oxygen,
Elemental Carbon and
ash.

The oxygen makes up cabin losses, the carbon is used for odor control. The ash accumulates in a dust bin, and doesn't add up to much.

http://www.sciencedirect.com/science...7311771500366X
http://www.h2o2.com/industrial/appli...s.aspx?pid=104

Ozone and hydrogen peroxide is made from water using electricity. This oxidises About 15% of the power needed for the air processing is required for waste water processing. The system, larger than needed at Earth, and larger than needed at Mars, is fully capable of recycling the water 100% from mixed wastes, as well and producing a slight surplus of oxygen and water from the concentrate. Sufficient to replace the inevitable losses in the system over a long duration flight.

With the ability to recycle water and air indefinitely, then crew and passengers totalling 14 passengers requires only 8.4 kg of concentrates per day - 105 days only 882 kg. Leaving a substantial payload capacity to carry added fuel, and hardware.

Total weight is 16.4 metric tons in LEO requires a delta vee of 3 km/sec to leave LEO and fly to the moon. It requires another 0.7 km/sec to enter lunar orbit. Another 0.7 km/sec to leave lunar orbit. From lunar orbit to land on the surface of the moon, requires a delta vee of 1.62 km/sec. To return to lunar orbit, another 1.62 km/sec.

A delta vee of 4.4 km/sec takes the craft from LEO to LLO and back. Using LOX/LH2 this requires 27.2 tonnes of propellant. That's 4.2 tonnes of LH2 and 23.0 tonnes of LOX. That's 60,000 litres of LH2 and 20,180 litres of LOX.

http://cessna.txtav.com/~/media/File...ion/x/xsd.ashx

With a diameter of 2 meters - six tanks that are 4.25 meters in length can be fitted around the central fuselage - which has an 8 meter long cabin.

With the propellant tanks fitted it looks something like this;

http://www.v2rocket.com/start/chapte...r-futuresm.jpg

Excepting the nuclear power plant is replaced with four inflatable solar collectors and the hypergolics of the 1950s is replaced with cryogenics, ultra-light tanks, and zero boil off systems that use MEMS based cryogenic coolers.

https://ntrs.nasa.gov/archive/nasa/c...0020017748.pdf

The people in Lunar orbit would be wearing a long-duration mechanical counter pressure suit, equipped with MEMS based life support hardware. They would also have MEMS based cryogenic propulsion units, that gave them the ability to leave the spacecraft land on the lunar surface and return to the spacecraft, which would then return to Earth.

https://www.youtube.com/watch?v=uRwnWMYpAi8

http://rocketbelt.nl/pogos/nasa-lunar-transport

With 85 kg including spacesuit 1000 to 1 Thrust to weight MEMS rockets and life support, requires 87 kg of propellant (73.6 kg LOX, 13.4 kg LH2) That's 191.2 litres of LH2 and 64.6 litres of LOX. With only 882 kg used as consumables, this leaves 4518 kg of spare lift capacity. So, if this is LOX/LH2 to drive the rocket belts - we can land and take off on the moon 52 times. This means that everyone of the 14 persons on board the ship can land and take off from the moon via rocket belt 3 times leaving 10 take offs and landings to spare - sold at a surcharge to those willing to pay for it! (explorer class tickets!, standard tickets have 3 locations)

People carry a few kg of hardware - an inflatable moon tent - for spending a night on the moon with a friend. Then return to the ship. If folks go down in pairs, that's 26 locations of interest visited by 52 people.

Visiting the Apollo 11 landing site would be an important detail. Though you will likely have to stay some distance away!

http://www.spacepolitics.com/2013/12...-uninterested/