A Space & astronomy forum. SpaceBanter.com

If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below.

Go Back   Home » SpaceBanter.com forum » Space Science » Policy
Site Map Home Authors List Search Today's Posts Mark Forums Read Web Partners

Using waste for propulsion ?



 
 
Thread Tools Display Modes
  #1  
Old November 25th 16, 02:28 AM posted to sci.space.policy
William Mook[_2_]
external usenet poster
 
Posts: 3,840
Default 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/








Ads
  #2  
Old November 26th 16, 01:32 AM posted to sci.space.policy
William Mook[_2_]
external usenet poster
 
Posts: 3,840
Default Using waste for propulsion ?

On Friday, November 25, 2016 at 7:56:57 PM UTC+13, JF Mezei wrote:
One thing Mr Mook forgot in his analysis:

Musk said his 100 pax ship to mars will be powered by methane.

This is why I wondered if collecting methane from human waste might make
sense, as well as burning/elejcting the rest of the waste. (accelerating
mass bacwards pushes ship forwards).

Even if the amount of methane produced is less than what it needed in
total, it still reduces how much you have to load at start of trip.

Unless the solid waste is needed on mars as fertilizer, you are best off
dumping t before you land since it is pointless to spend fuel to
decelerate and land that mass. And if you're going to eject it, you
might as well do more than mereley throw it is, you should accelerate it
to use it as propulsion.


Propelled by Methane and LOX - that's different than the crew systems being powered by methane. The amount of methane consumed during launch, and boost into Mars transfer trajectory is vastly larger than the amount of methane produced from life support processes.

http://www.space.com/34210-elon-musk...lony-ship.html

A well designed life support system reuses ALL products within the life support system using a modest amount of energy derived from direct solar power to produce

Water (recycled)
Oxygen (recycled)
Carbon black (odor absorber)
Ash (micronutrients used for fertiliser)

from the waste products (including breathing)

As shown, 2.1 kW is suffiicent to fully recycle all the waste from 14 people. So, 100 people requires 15 kW of continuous power. This power can be obtained from concentrating solar photovoltaics which produce about 22 kW per kg of payload at 1 AU and produce about half that at Mars distance.

https://solarthermalmagazine.com/wp-...s_CPV-zoom.jpg

https://web.archive.org/web/20131228...V/Mac_Mook.gif

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

Most large cruise ships have about 4,000 cubic feet of cabin space per passenger (227 cubic meters per couple). So, fifty couples would take 11,350 cubic meters. A sphere 28 meters in diameter (92 ft) houses 100 people at the same densities as large cruise ships. 12 levels across the diameter produces 11 floors - one central floor and 5 pairs of floors.

L x Radius Area

0 0 14.00 615.75
1 2.2 13.83 600.55
2 4.4 13.29 554.93
3 6.6 12.35 478.90
4 8.8 10.89 372.47
5 11 8.66 235.62

**** **** Total 5,716.44

SF SM Cabins
183 17.01 336 - Luxury suite cruise ship
450 41.83 136 - Luxury suite Waldorf Astoria
600 55.77 102 - Luxury suite Waldorf Towers

So, with a luxury cabin with two persons each, you need fifty cabins of that size for 100 passengers. So, half the 'floor space' is taken up by cabins and the rest for 'public space'.

http://www.lpi.usra.edu/lunar/strate...manstoMars.pdf

http://trs-new.jpl.nasa.gov/dspace/b.../1/09-3642.pdf

An array of concentrating photovoltaics have the capacity to generate 500 kW of power at 1 AU- far more than needed to fully recycle 100% of the air and water, and reduce surplus to elemental carbon and micronutrient ash (which is used for fertilisers when on Mars). The mass of a well designed system would be around 25 kg.

For a Mars mission I like the idea of using very high altitude aerobraking to bring the spacecraft onto the surface of Diemos.

http://www.spacefuture.com/archive/t..._company.shtml

And then use water found there and the copious solar power available to create hydrogen and oxygen propellants for supplying rocket belt descents to the Martian surface.

0.87 km/sec is required to take an object from Diemos to Low Mars Orbit.


23,459.0 km - Diemos semi-major axis
3,396.2 km - Mars equatorial radius

5.03 km/sec - Mars escape velocity
3.55 km/sec - Mars Orbital Velocity (low Mars orbit)
1.35 km/sec - Diemos orbital velocity

So, once landed on Diemos, with a spare 200 kW of electrical power - you can break down water ice (if any) into hydrogen and oxygen at a rate of 5.077 litres per hour. Hydrogen is made at a rate of 0.564 kg/hour and oxygen at a rate of 4.513 kg per hour. Using LOX/LH2 hat a O/F ratio of 5.5/1.0 that means that 0.564 kg/hour of hydrogen is combined with 3.103 kg/hour of LOX leaving 1.410 kg/hour of LOX to spare.

Now, to boost from Diemos to Low Mars Orbit requires a delta vee of 0.67 km/sec. After 1.927 hours the person with rocket belt skips into the Martian atmosphere moving at 4.701 km/sec. Aerobraking is used to bring the traveller down to zero speed and zero altitude - using only 0.20 km/sec. Skipping off the atmosphere back into orbit, after slowing to 3.551 km/sec - enters LMO. So, the delta vee to move from Diemos to LMO or the Martian surface itself ranges from 0.67 km/sec to 0.87 km/sec.

On the surface of Mars it takes 3.551 km/sec to enter LMO and another 1.145 km/sec to boost back up to Diemos in 1.927 hours.

Diemos -- Mars 0.67 km/sec - LMO
0.87 km/sec - Mars Surface

Mars -- LMO 3.551 km/sec
LMO -- Diemos 1.145 km/sec

A total delta vee of 5.566 km/sec is sufficient to carry an astronaut to the Martian surface and back to a ship stationed at Diemos. This requires 200 kg of propellant for an 85 kg astronaut in a long duration pressure suit. This includes 30.8 kg of LH2 occuping 439.6 litres of volume and 169.2 kg of LOX occuping 148.4 litres of volume. A total of 200 kg of propellant occupying 588 litres. Four tanks carrying 50 kg each of propellant. Spherical tanks 655 mm in diameter (25.78") with a 414 mm diameter (16.29") LOX tank inside each.

Providing ice is found on Diemos, sufficient propellant is generated to send 6 people to Mars and back via rocket belt every day. Virtually the entire passenger complement every two weeks!
  #3  
Old November 26th 16, 06:55 AM posted to sci.space.policy
Fred J. McCall[_3_]
external usenet poster
 
Posts: 10,018
Default Using waste for propulsion ?

JF Mezei wrote:

On 2016-11-25 19:32, William Mook wrote:

Propelled by Methane and LOX - that's different than the crew systems being powered by methane. The amount of methane consumed during launch, and boost into Mars transfer trajectory is vastly larger than the amount of methane produced from life support processes.


Launch and escape from earth are not a concern as launch is done with
fuel from ground over many launches to bring fuel up. And escape from
Earth would happen well before the passenger waste would have generated
significant amoumt of methane.

However, the methane generated during the 90 or more days to mars would
help *reduce* amount of fuel needed to get into Mars orbit and then
de-orbit.

If human waste produces methane, does it make sense to use energy to
recycle methane to something else when you can use it almost directly
for engines ?


You can't 'use it almost directly', there's not very much of it, and
whatever mass you don't recycle you have to replace with supplies to
make up for the lost recycled materials. This makes you burn MORE
fuel, not less.

You're stuck on a stupid idea. Get over it.


--
"Some people get lost in thought because it's such unfamiliar
territory."
--G. Behn
  #4  
Old November 26th 16, 03:13 PM posted to sci.space.policy
Jeff Findley[_6_]
external usenet poster
 
Posts: 2,307
Default Using waste for propulsion ?

In article om,
says...

On 2016-11-25 19:32, William Mook wrote:

Propelled by Methane and LOX - that's different than the crew systems being powered by methane. The amount of methane consumed during launch, and boost into Mars transfer trajectory is vastly larger than the amount of methane produced from life support processes.


Launch and escape from earth are not a concern as launch is done with
fuel from ground over many launches to bring fuel up. And escape from
Earth would happen well before the passenger waste would have generated
significant amoumt of methane.

However, the methane generated during the 90 or more days to mars would
help *reduce* amount of fuel needed to get into Mars orbit and then
de-orbit.

If human waste produces methane, does it make sense to use energy to
recycle methane to something else when you can use it almost directly
for engines ?


Gnat's farts. In the big scheme of things, you're not going to want to
use methane produced from human waste for propulsion. We're talking
mass fractions here. What fraction of the overall spacecraft mass is
the methane produced? Maybe you'd use it for maneuvering thrusters,
maybe. But "propulsion" is laughable.

Jeff
--
All opinions posted by me on Usenet News are mine, and mine alone.
These posts do not reflect the opinions of my family, friends,
employer, or any organization that I am a member of.
  #5  
Old November 26th 16, 04:05 PM posted to sci.space.policy
Fred J. McCall[_3_]
external usenet poster
 
Posts: 10,018
Default Using waste for propulsion ?

JF Mezei wrote:

On 2016-11-26 00:55, Fred J. McCall wrote:

You can't 'use it almost directly', there's not very much of it, and
whatever mass you don't recycle you have to replace with supplies to
make up for the lost recycled materials. This makes you burn MORE
fuel, not less.


So you're suggesting methane and human waste be thrown out the door in
flight then ?


Mr Mezei, stop listening to the voices in your head and just assume
I'm saying what I actually said.


Hint: on ISS it is put in plastic bags and then sent to the great big
Progress Incinerator. Methane isn't recycled.


Hint: A Mars vehicle isn't ISS.

Hint: Solid human waste doesn't just magically turn into methane.

Hint: You're the one apparently suggesting throwing big flaming bags
of **** out the back of the vehicle. Look up 'rocket'.


On a trip to Mars, thre isn't a regular Progress that comes it with
fresh pizza and goes back with garbage that is burned.


No ****, Sherlock.


So human waste handling is an issue Musk will have to deal with on its
big 100pax ship because there is going to be a hell of a lot more of it.
I was merely proposing a means to use it as propulsion instead of
speding much energy to try to convert it or just dumping it overboard


Except you weren't. You were automagically turning it all into
methane by waving your magic willie and then acting as if that's
useful.


--
"Some people get lost in thought because it's such unfamiliar
territory."
--G. Behn
  #6  
Old November 27th 16, 02:22 AM posted to sci.space.policy
William Mook[_2_]
external usenet poster
 
Posts: 3,840
Default Using waste for propulsion ?

On Saturday, November 26, 2016 at 3:04:23 PM UTC+13, JF Mezei wrote:
On 2016-11-25 19:32, William Mook wrote:

Propelled by Methane and LOX - that's different than the crew systems being powered by methane. The amount of methane consumed during launch, and boost into Mars transfer trajectory is vastly larger than the amount of methane produced from life support processes.


Launch and escape from earth are not a concern as launch is done with
fuel from ground over many launches to bring fuel up.


The amount of methane is very large on the order of centuries worth of waste production, even if you count everything as methane, which it is not. So, as such it is impractical. Further, methane in the life support system is more valued as a source of hydrogen and zeros out the need to bring ANYTHING in the form of water or oxygen.

So, when you drink water, eat food and breathe oxygen you generally get;

2 O2 + food + water --- energy + CO2 + 4 H2O + other waste

Solar powered electrolysis recovers hydrogen;

4 H2O + solar energy -- 4 H2 + 2 O2

Sabatier reaction absorbs CO2 from the air making methane and water again;

CO2 + 4 H2 -- CH4 + 2 H2O

Methane is pyrolysed using solar energy to reduce methane to carbon and hydrogen again;

CH4 + solar energy --- C + 2 H2

Some water is converted to H2O2

2 H2O + O2 + solar energy -- 2 H2O2

H2O2 is used to convert other waste to CO2 and H2O and ash through oxidation

other waste + 2 H2O2 -- 2 H2O + CO2 + ash

That CO2 goes back to the Sabatier process to restore the oxygen and produce carbon black.

The carbon black once produced is used to absorb odors.


And escape from
Earth would happen well before the passenger waste would have generated
significant amoumt of methane.


The passengers never generate a significant amount of methane relative to the propellant. That's the point.

However, the methane generated during the 90 or more days to mars would
help *reduce* amount of fuel needed to get into Mars orbit and then
de-orbit.


While its true that if you throw stuff overboard it makes sense to reuse what you can as propelant, the amounts are minor, and there are better uses in a CLOSED CYCLE SYSTEM. Such a closed cycle system is ALREADY OPERATING ABOARD THE ISS. So, assuming waste is tossed overboard as in Apollo, is wrong.

So we're comparing reusing methane and other wastes in the life support system to close as many loops as possible to reusing methane as propellant. When used as propellant the advantage is not as great as using methane as a closed cycle feedstock. Relative to the cost in life support supply weight when used as propellant you are way ahead using it as closed cycle feedstock.

Remember, methane coming from waste starts out as water, oxygen and sugar or oil. Using methane in the life support process to restore hydrogen supplies at low cost, and converting CO2 to CH4 using hydrogen made in this way (along with water conversion as needed) - radically reduced payload mass, which radically reduces propellant.

Let's look at a worst case situation. Let's look at a METHANE LOX rocket in LEO before departing for Mars. Let's say we look at a 280 day mission for 100 people consuming 3.65 kg per day. That's 28,000 person days and 102.2 metric tons of consumables. The persons themselves mass 85 kg each so that's 8.5 metric tons. We have another 42.5 metric tons of other hardware.. So, this is what you start with. On the 90th day you arrive at Mars and you've used 32.85 tonnes of consumables, and you've held on to it to use as propellant.
LEO--TMI TMI--Mars Mars--TEI
Consumables: 102.2 metric tons 69.35 tons 32.85 tons
Passengers: 8.5 metric tons 8.50 tons 8.50 tons
Structure/tools: 42.5 metric tons 42.50 tons 42.50 tons

TOTAL 153.2 metric tons

So, to land on Mars, requires a delta vee of 1 km/sec with aerobraking. To enter a Mars transfer orbit requires a delta vee of 3.7 km/sec. To take off from Mars and fly to Earth requires 5.9 km/sec from the surface on the 190th day.

Now let's be generous and say ALL the consumables end up as CH4 (which isn't the case) it DOES turn out that the amount of methane used to enter Mars atmosphere and land on Mars, is about equal to the amount of all the supplies thrown away if we were to throw them away;

LEO--TMI TMIMar MarTEI
- 124.83 263.53 O2 needed
- 32.85 69.35 Methane
102.20 69.35 32.85 Supplies
8.50 8.50 8.50 Personnel
42.50 42.50 42.50 Structure
153.20 120.35 83.85 Payload

3.70 1.00 5.90 Delta Vee
0.6484 0.2461 0.8111 u
0.1351 0.0513 0.1690 Methane Fraction
0.5133 0.1948 0.6421 Oxygen Fraction
0.3516 0.7539 0.1889 p

1,905.80 637.27 443.94 Stage Weight
1,235.68 156.83 360.09 Propellant Weight
257.43 32.67 75.02 Methane
978.24 124.16 285.07 Oxygen


Now a 640 tonne payload launched by a Mars Colonial Transport requires three fueling launchers to (the original launch plus three added launches) to accumulate sufficient propellant. The 32.67 tonnes is replaced by the methane in this idealised scenario (which is way more than you'd actually get, and then there's the equipment to recover and store the methane as well).

However, if we use the methane to recover the hydrogen for use in a closed cycle system AND DON'T THROW ANYTHING AWAY as described previously, the mass of consumables is reduced from 102.2 tonnes of consumables to 8.4tonnes of concentrates and other consumables by reusing all the water and oxygen for 280 days! A savings of 93.8 tonnes throughout!

8.40 5.70 2.70 Supplies
8.50 8.50 8.50 Personnel
42.50 42.50 42.50 Structure
59.40 56.70 53.70 Payload

3.70 1.00 5.90 Delta Vee
0.6484 0.2461 0.8111 u
0.1351 0.0513 0.1690 Methane Fraction
0.5133 0.1948 0.6421 Oxygen Fraction
0.3516 0.7539 0.1889 p

1,091.51 381.10 284.31 Stage Weight
707.71 93.79 230.61 Propellant Weight
147.44 19.54 48.04 Methane
560.27 74.25 182.57 Oxygen

Here we have only ONE ADDED fuel flight - cutting launches in half.



If human waste produces methane, does it make sense to use energy to
recycle methane to something else when you can use it almost directly
for engines ?


Yes. Since you cannot use it directly since it has to be cleaned up for use, and since there isn't that much methane anyway, and since it can be used just as easily as a source of hydrogen gas by pyrolysing it.


  #7  
Old November 27th 16, 04:12 AM posted to sci.space.policy
Fred J. McCall[_3_]
external usenet poster
 
Posts: 10,018
Default Using waste for propulsion ?

JF Mezei wrote:

On 2016-11-26 10:05, Fred J. McCall wrote:

Except you weren't. You were automagically turning it all into
methane by waving your magic willie and then acting as if that's
useful.


So, what is your opinion on how a ship filled 100 people for months
should handle/process human waste ?


NASA is apparently doing studies about turning it into food.


When designers go through great strides to shave off a percent here and
there to reduce ship's mass, wouldn't the ability to generate fuel from
waste during the journey also help shave a percent here and there?


Yes, magic would be quite handy. Until you specify precisely how you
think you're going to turn solid human waste into methane, magic is
what you're talking about. You see, there is a lot of, well, crap in
human waste. You can't just wave your magic willie and turn it into
methane. Even if you could, how do you get it from the 'digester'
into a high pressure fuel tank?


--
"Some people get lost in thought because it's such unfamiliar
territory."
--G. Behn
  #8  
Old November 27th 16, 07:17 AM posted to sci.space.policy
Fred J. McCall[_3_]
external usenet poster
 
Posts: 10,018
Default Using waste for propulsion ?

JF Mezei wrote:


100pax over 3-4 months will consume large amounts of food. That is a lot
of mass that you have to lift and accelerate out of earth's orbit
towards mars most of which will become waste. Not doing anything with it
means wasting that mass which you spent much fuel accelerating.


I know it's hard for you, but think about it. Most of the mass of
food (and feces) is water. You're going to get the water back for
recycling on the back side of the process. That means each person
will generate 1-2 ounces of solid waste per day once the water has
been recovered (and you'll get 3-6 ounces of water out of the same
waste stream). Let's use the larger number as more 'favorable' to
your case; 100 people (not sure what 'pax' are when they're up and
dressed) will generate around 12.5 pounds of solid waste per day. That
waste is a mix of dead bacteria, indigestible food elements like
cellulose, minerals, and indigestible fats. You're not going to turn
it into methane without giving up a lot of the recovered water and
even then most of it isn't going to 'convert'. Recovering the water
is more valuable, since you can make things like breathing air out of
that stuff. So you're going to accumulate a little over half a ton of
such cruft during the course of the trip.

Not much it can be used for, which is why they throw it away on ISS.
One of the reasons NASA is starting research on turning it into food
(growing fresh veggies and such) is the high mineral content; some
10%-20% by weight is minerals.

You know, this is a 'sci' newsgroup. Instead of just latching onto an
idea and defending it to the death, do some research yourself. It's
really not that difficult.


--
"Some people get lost in thought because it's such unfamiliar
territory."
--G. Behn
  #9  
Old November 27th 16, 07:45 AM posted to sci.space.policy
Fred J. McCall[_3_]
external usenet poster
 
Posts: 10,018
Default Using waste for propulsion ?

JF Mezei wrote:

On 2016-11-26 22:12, Fred J. McCall wrote:

Yes, magic would be quite handy.


Are you aware that on earth, there are some power plants already bult
next to dump sites that collect the methane that is produced from
decomposition and power the turbines to produce electricity ? It isn't
magin.


Are you aware of how that **** works? It's not at all what you're
talking about wanting to do, it's not in space, and it involves 'dump
sites' not '****e sites'. See my other posting on this topic. Then
read this:

https://www.britannica.com/science/feces


human waste. You can't just wave your magic willie and turn it into
methane. Even if you could, how do you get it from the 'digester'
into a high pressure fuel tank?


I never suggested the tech was "space ready". But it exists already.


No, it doesn't. What can be done here on Earth with a garbage dump
containing thousands of tons of food garbage gestating for years and
what can be done with relatively tiny amounts of dried human waste
over a few months are so different as to not be comparable in any way.

https://en.wikipedia.org/wiki/Landfill_gas_utilization


And
leveraging the power of crap has not been implemnented in space flight
yet because that is just bagged and disposed of.


No. Leveraging the power of crap has not been implemented in space
flight yet because it isn't particularly practical, which is why it is
just bagged and disposed of.


And spaceflight has
never had systems scaled for 100 passengers on a ship. So ECLSS systems
on a 4 month journey will have to deal with crap for 100 pax one way or
the other.


What the **** is a 'pax'? If you mean 'passenger', write 'passenger'.
Once the water is removed there will be around half a ton of solid
'crap' accumulated during the whole trip. You could store it in a
closet.


Unless, of course, the food consists of pills and water and people are
put into induced comas or whatever lethargic state.


Don't be silly.


Look at how much NASA and Russia spent to develop support for 6
cremembers for a few months. Now, you have to scale it to 100 humans for
3-4 months each way. (and this assumes the ships is restocked from
scratch on Mars with food/air/water/fuel for return journey. (as opposed
to stocked for both journeys uypon departing earth).


Your argument doesn't make any sense at this point. You are going to
have to carry food, water, air, and fuel REGARDLESS of what you do
with the half ton of desiccated ****e at the Mars end of the journey.


--
"Some people get lost in thought because it's such unfamiliar
territory."
--G. Behn
  #10  
Old November 27th 16, 02:24 PM posted to sci.space.policy
Alain Fournier[_3_]
external usenet poster
 
Posts: 548
Default Using waste for propulsion ?

On Nov/27/2016 at 1:17 AM, Fred J. McCall wrote :
JF Mezei wrote:


100pax over 3-4 months will consume large amounts of food. That is a lot
of mass that you have to lift and accelerate out of earth's orbit
towards mars most of which will become waste. Not doing anything with it
means wasting that mass which you spent much fuel accelerating.


I know it's hard for you, but think about it. Most of the mass of
food (and feces) is water. You're going to get the water back for
recycling on the back side of the process. That means each person
will generate 1-2 ounces of solid waste per day once the water has
been recovered (and you'll get 3-6 ounces of water out of the same
waste stream). Let's use the larger number as more 'favorable' to
your case; 100 people (not sure what 'pax' are when they're up and
dressed) will generate around 12.5 pounds of solid waste per day. That
waste is a mix of dead bacteria, indigestible food elements like
cellulose, minerals, and indigestible fats. You're not going to turn
it into methane without giving up a lot of the recovered water and
even then most of it isn't going to 'convert'. Recovering the water
is more valuable, since you can make things like breathing air out of
that stuff. So you're going to accumulate a little over half a ton of
such cruft during the course of the trip.


[You should use normal units instead of those ounces and pounds, it
would make your post easier to read for normal people, and lessen the
risk of errors from unit conversions.]

It's not one or the other. You can very well recover the methane and the
water and grow food. Plants don't need the methane from human waste to
grow. So after extracting methane, the waste isn't any less fertile than
it was before extraction.

If you want to recuperate the water that was lost in the fermentation,
you can burn the methane and make electricity, water and CO2. The CO2
will be taken by the plants you want to grow. Of course, if you do so,
that means you can't use Mr Mezei's idea of burning the methane as
rocket propellant. Which probably isn't worth the trouble anyway.

Even growing food on the spaceship probably isn't worth the trouble. The
trip is not long enough to do serious farming. I think that the best use
of human waste on a spaceship bringing colonists to Mars is to store it.
Land it on Mars. And then, once on Mars compost it and use it to grow
food. You will want to have lots of fertilizer handy for your colony on
Mars.


Alain Fournier

 




Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Novel Lorentz propulsion for interplanetary and interstellar propulsion. Robert Clark Astronomy Misc 5 August 24th 11 10:14 PM
ot well that was a waste of time Brian Gaff Space Shuttle 0 August 17th 09 06:20 AM
Waste not! prof-rabbit Astronomy Misc 0 July 28th 09 09:33 AM
Such a Waste of Energy G=EMC^2 Glazier Misc 2 July 28th 06 07:04 PM
So far Titan a waste starlard Amateur Astronomy 25 August 10th 04 08:34 PM


All times are GMT +1. The time now is 08:51 PM.


Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2021, Jelsoft Enterprises Ltd.
Copyright 2004-2021 SpaceBanter.com.
The comments are property of their posters.