Argon-Otto cycle Engine for Lunar Applications

[sniffy]

Argon-Otto cycle Engine for Lunar Applications

What would be the equivalent of Bobcat or tractor on the moon? An internal combustion engine is impossible. Electric motors are susceptible to solar storms and extremely heavy. The task is to use what is there; however, an off the shelf argon laser seems ready to go.
70-120 VDC
3.0-10.0 Amps
1200 Watts
www.laserdrive.com/argon.cfm?pl=2,1

Ok, so what in the world does this have to do with a gas powered (Otto cycle) engine? Just a review:
1. Intake
2. Compression
3. Ignition, power stroke
4. Exhaust.

Some may have already deduced that the engine head is simply the argon laser and it will flash the liquid argon for the ignition and power stroke. The exhaust is cooled for intake, compressed, and the cycle repeats itself. Unlike a car engine, this is a closed system.

Theoretical efficiency of a gas engine is about 50%, but even in a lab there is a practical limit of about 25%. The Argon-Otto system is run by electricity, close to 100% efficiency is preferred. What is the bottom line? This is given as

Efficiency = 1 - compression ratio ^ heat capacity of the gas.

The compression from gas to liquid argon is in the ratio of 1 to 1000. For gasoline engine this can only be 1 to 10. The Argon engine could, at least in theory, operate near 100% efficiency.

[Grand Lunar]

Electric motors worked just fine for the rover on Apollo. And they work just as well for the MERs too.

[Tanalia]

It's not clear what you mean by "the engine head is the argon laser". A gas laser tube is little more than a glass tube with mirrors at the ends; it has nothing like a piston to generate mechanical motion. If you meant that the laser is the heat source for a closed-cycle engine which also happens to use argon as a working fluid, then you should know that argon lasers are extremely inefficient -- the 1200 Watt power supply you linked is the type commonly used to power 500 milliWatt argon lasers.

AS GL pointed out, electric motors work fine, and can be made with over 95% efficiency.

[sniffy]

The idea is to have an intenal combustion engine that "ignites" at room temperature. It may very well be impossible. I used argon since there is some on the moon, as well as 1% in the Earth's atmosphere. Argon is an essential industrial material; in particular for metallurgy.

It may very well be impossible, and as you point out, I read the specifications incorrectly. Thank you for the correction.

"Electric motors work just fine" .... $600 million dollars for a rover that is used just once. Are you against mining and industrial applications on the moon?

0:19:08 The cost of the programme, whose sole goal was to be the first to plant a flag on the lifeless rock just outside the earth, if adjusted for inflation to the 21st century, was $135 billion.

There are spin-offs from space progamms, such as the (integrated circuit) computer. The main selling point is that new technologies are developed; and, it kills fewer people than war.

[sniffy]

Microwave might be better to fire the liquid argon:

www.microwaves101.com/encyclopedia/efficiency.cfm

MESFET amplifiers with 10% bandwidth can exceed 30% efficiency at X-band. PHEMT amplifiers can exceed 40% PAE at X-band. TWTs routinely deliver 60% efficiency.
MESFET amplifiers with 10% bandwidth can exceed 30% efficiency at X-band. PHEMT amplifiers can exceed 40% PAE at X-band. TWTs routinely deliver 60% efficiency.

It is interesting that power efficiency is inversely proporsional to bandwidth.

In signal applications noise increases with bandwidth. Only a phase-locked loop can send/recieve a low power signal from deep space to earth. It has a bandwidth of a hertz or so.

[PhantomWolf]

"Electric motors work just fine" .... $600 million dollars for a rover that is used just once.

The major cost of the Rovers wasn't in creating new parts, it was in figuring out how to design a new type of vehicle from scratch. In comparison to other vechiles of the time, the research costs were comparable, consider the Jeep Wagoneer which was a development of existing technology and construction techniques. It still cost a third of the rovers to develop. The difference is that the cost of the Rovers was only spread over a limited number of units, unlike a convential vehicle.

[sniffy]

I don't know the cost of the lastest rover, or Chariot as it's called. It is mentioned in da bizness of da outa space.

www.space.com/businesstechnology/080312-technov-nasa-chariot.html
Vehicle Mass
earth 2000 kg
moon 1000 kg

The tab to park it on the moon should be around a billion dollars!

[smlbstcbr]

Oct 4, 2008 17:51:10 GMT -4 sniffy said:

I don't know the cost of the lastest rover, or Chariot as it's called. It is mentioned in da bizness of da outa space.

www.space.com/businesstechnology/080312-technov-nasa-chariot.html
Vehicle Mass
earth 2000 kg
moon 1000 kg

The tab to park it on the moon should be around a billion dollars!

But this is not a simple vehicle. It's more an utility wagon than a rover and, as mentioned in the other posts, the vehicle is being developed from scratch. Considering how expensive things are here, it's a real life budget. You are not taking into account a fact that kills an internal combustion engine to get to moon, at least concerning the vehicles for exploration: fuel. No matter if it's petroleum or argon, they have to be taken from earth. That would be extremely expensive. The very nice and simple electric motor would perform like a charm. Just needs a battery and a solar panel to get free energy from the sun, saving millions in transportation costs.

EDIT: I forgot, an electric motor has a maximum torque at low RPMs, the Otto-cycle engine only delivers power at a very narrow band of RMPs. Another issue that you are forgetting is Thermodynamics: you cannot obtain something from nothing. The first posts clearly breaks this. You need energy to do all the cycle, once you have expanded the gas, you need energy from somewhere to compress it and cool it.

[sniffy]

I hope you don't get too bothered because I like my own ideas.
Heat flows from hot to cold. From that you derive that a heat engine has to discard heat to the cold resorvior, and by some long winded aurgument you can say that you can't get something for nothing.

In this case, the energy comes from the battery and goes to the microwave. The fluid-gas is just a medium.

The Otto-Argon cycle, to the best of my knowledge is my own crackpot idea, opinions expressed here are not nescesarily those of everybody else.

There is some argon atmosphere on the moon, which is why a chose it in the first place.

Torque and electric motors is quite a topic. I'm sure that part is done by experts.

[JayUtah]

Electric motors work fine, are efficient, and work reliably. That is the most important aspect of human-rated technology, not how many buzzwords you can cram into the idea. You don't use experiment notions where mission- and life-critical applications are being developed.

$600 million is a credible vehicle concept development budget in the automotive industry.

[sniffy]

We do not use buzzwords on this great site. The authors subscribe to the highest ideals and have no connection whatsoever to the porkbarrel.

Economic and elegant use of materials is of the highest priority in the space race. An old example is this image from Lascaux. Count the number of prongs on the Red Deer. Does number that mean anything?

[smlbstcbr]

Oct 5, 2008 0:20:36 GMT -4 sniffy said:

I hope you don't get too bothered because I like my own ideas.
Heat flows from hot to cold. From that you derive that a heat engine has to discard heat to the cold resorvior, and by some long winded aurgument you can say that you can't get something for nothing.

In this case, the energy comes from the battery and goes to the microwave. The fluid-gas is just a medium.

The Otto-Argon cycle, to the best of my knowledge is my own crackpot idea, opinions expressed here are not nescesarily those of everybody else.

There is some argon atmosphere on the moon, which is why a chose it in the first place.

Torque and electric motors is quite a topic. I'm sure that part is done by experts.

Hang on a sec. This is not a Otto cycle, it's a Stirling one. However, some modifications could actually make this work, theoretically: if you replace the heat source by a resistance you have a heath source that's 100% effective at turning electricity into it. But there are disadvantages. While an electric motor only has three moving parts (the rotor and the bearings), an Stirling engine has a crankshaft, the con rods, the bearings, the gearbox and other bits and pieces. You need to simplify the operation of the machines that are going to be taken to the Moon. A electric motor is very very simple and its transfer function is inherently a negative feedback loop.

[sniffy]

There are two practical problems so far:

Lasers are NOT efficient.

Microwave will not heat or flash Argon. Microwave must operate on a a dipolar molecule such as water.

Water of course, is great for a heat engine; it was always used in the first place.

The heat engine is modeled as close as possible to the real thing:
Otto, Diesel, Sterling, Carnot cylce, whatever. To be honest, I find the Otto cycle eaier to do calculations.

On a different topic, generation of large amounts of power is by steam turbine. The steam turbine does not have fewer parts; however the linkage is simpler--no pistons and connecting rods. Good observation!
Did you notice that there are 18 prongs on the deer's antler?

[sniffy]

Just checking sterling engine, seems that a microwave would make more sense than a heat exchanger.

www.sesusa.org/

The modern Stirling Engine is a clean and efficient engine. This is because the heat driving the pistons is supplied from outside the engine and transferred through heat exchangers to the piston volumes. Thus the creation of pollutants such as NOx can be avoided. The external combustion aspect enables a Stirling Engine to operate equally well on multiple types of fuel, such as natural gas, propane, gasoline, diesel, ethanol85, bio-diesel or even heat from the sun. The extra quiet operation of the Stirling Engine is one of the engines best features. Many Stirling engine configurations are balanced by the nature of their construction, and since the fuel is burned slowly and constantly outside the engine, there are no explosions to muffle.

[JayUtah]

Economic and elegant use of materials is of the highest priority in the space race.

Not at the cost of reliability when human-rated technology is at stake. Space engineering routinely opts for proven technology over newfangled stuff.