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#101 2017-11-16 20:19:52

Oldfart1939
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Registered: 2016-11-26
Posts: 979

Re: Land propulsion - Tracks, or tires?

kbd512-

Thanks for the upgraded info. My experience was in ancient historical times with the then brand new M113s which had an awful tendency to throw tracks. I received training on driving one of the ambulance versions and was continually reminded to never drive in a contour profile on any sort of steep slope or "the tracks are history."

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#102 2017-11-19 19:45:02

kbd512
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Registered: 2015-01-02
Posts: 1,187

Re: Land propulsion - Tracks, or tires?

Oldfart1939,

The new T150F track links from United Defense have a tested design life of about 19,000km on a 30,000lb M577 variant of the M113, but 10,000km to 15,000km is more realistic life span over the varied terrain such a vehicle may encounter.  Each T150F track link weighs 24.3lbs, so 3,086.1lbs for both tracks, 63 (left side) and 64 (right side).  These new tracks were also designed to reduce shedding.

The rubber band tracks I proposed using give tracked vehicles ride quality, noise, and vibration similar to heavy wheeled vehicles like semis, assuming a similar suspension system.  The minimum design life for rubber band tracks is 8,000km at a 30,000lb GVW.  Rubber doesn't last quite as long as forged steel, but the band tracks also incorporate additional design features intended to inhibit track shedding over the T150F.  The weight is approximately 50% of the steel track, so basically divide the T150F weight by 2.  Segmented band tracks make track replacement easier.  The track band is divided into 4 segments per track.

M113A3's equipped with steel or band tracks can attain the same road speed as the Stryker, assuming the governor is removed, but sharp turns at highway speeds would shed tracks.  The M113A3 has a road range of 480km with 95 gallons of diesel using the ancient Detroit Diesel 6V53T.  The Stryker, a substantially heavier vehicle, achieves an impressive 530km using just 53 gallons of diesel.  That said, a substantially heavier hybrid M113 equipped with band tracks achieved a 965km road range.  A hybrid Stryker could easily double its road range.  The catch is that that is road range.  The fuel economy of the Stryker starts to look a lot like the fuel economy of the M113 in an off road environment.

Anyway, the point is that technology for all types of military vehicles has improved greatly since you were in the Army.  That's why we have TARDEC.  Incidentally, TARDEC and ARPA are responsible for the far more fuel efficient OPOC systems going into the new trucks that Oshkosh is making for the US Army.  Eventually, batteries and electric motors will replace the diesel prime mover.  These people should be working with Tesla to electrify their trucks to dramatically reduce dependency on fossil fuels, an ever-present danger and logistical nightmare in a war zone, both because the product itself is flammable and because running out typically means a halt to operations in the best case scenario and death if the enemy decides that's a good time to attack.

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#103 2017-11-20 07:27:53

Terraformer
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From: Lancashire
Registered: 2007-08-27
Posts: 2,508
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Re: Land propulsion - Tracks, or tires?

I wonder if a radioisotope generator would work for a long distance truck, whether on Mars or Terra? What power to weight ratio would be needed? I think Strontium-90 could achieve ~0.1 kW/kg. Coupled with batteries, unless you want to continually move to use up the power.


"I guarantee you that at some point, everything's going to go south on you, and you're going to say, 'This is it, this is how I end.' Now you can either accept that, or you can get to work." - Mark Watney

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#104 2017-11-20 14:13:32

RobertDyck
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From: Winnipeg, Canada
Registered: 2002-08-20
Posts: 5,043
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Re: Land propulsion - Tracks, or tires?

Terraformer wrote:

I wonder if a radioisotope generator would work for a long distance truck, whether on Mars or Terra? What power to weight ratio would be needed? I think Strontium-90 could achieve ~0.1 kW/kg. Coupled with batteries, unless you want to continually move to use up the power.

That's a good idea. As you implied, couple that with modern hybrid technology. Regenerative brakes recover energy from vehicle motion to produce electricity that recharges the batteries. That power is used to accelerate again. That means stopping and starting takes a fraction of the power, reducing power required. Modern hybrids operate the engine at maximum efficiency, even if the vehicle doesn't need that much power right now. The engine runs a generator, that power is stored in batteries. The electricity is used when needed. You can replace the gasoline engine with any generator, do the same thing. Actually, railroad locomotives have done this with diesel for over a century. They stated developing diesel hybrids in the early 1890s, finally got it to work in the late 19-teens, went into production in 1920. All diesel locomotives are hybrids. Some big ocean ships now use azimuthing pods; they do the same thing but with really big engines and electric motors. In the late 1980s, those operating subway systems talked about regenerative breaks, but they wanted to put the power back in the power rails, to power other trains. They didn't think of on-board batteries. That's a relatively new refinement.

I would suggest Potassium-40. That's a radioactive isotope that's so low level it isn't regulated. You can buy it without any special license. It decays by beta decay, so a beta-voltaic cell could capture the radiation. The interesting thing about this isotope is it's sensitive to a modulated magnetic field. Properly modulated, the magnetic field causes the atoms to decay much faster. This is something science said shouldn't happen, but it does. Traditional science believes nothing changes the rate of decay of any isotope, but this one can be affected. That means you can cause rapid release of energy when you need it, turn it off when you don't. And beta radiation is so weak it can be blocked by a single sheet of paper, or a single layer of plastic film. A beta-voltaic cell works on the same principle as photovoltaic, but obviously uses beta radiation instead. Potassium-40 will be consumed as you produce energy, it will have a limited range, but the range should be much greater than chemical fuel.

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#105 2017-11-20 18:46:37

RobertDyck
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From: Winnipeg, Canada
Registered: 2002-08-20
Posts: 5,043
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Re: Land propulsion - Tracks, or tires?

Hmm. Technical details of the K40 reactor are sketchy. Few people are working on it. One wants to enhance electron capture by bombarding it with electrons. One periodic table claims K40 has half-life of 1.277 x 10^9 years, another says 1.248 x 10^9 years. It naturally decays 89.28% via electron capture (EC), 10.72% via beta emission (β+). The EC mode can be further divided, over 99% really is electron capture, less than 1% is via positron emission (β-). There is some question about how EC happens, some people think this is actually positron (β-) emission, but it gets annihilated by impact with an electron (β+) in an electron shell.

If increased K40 decay is in the form of EC or β-, then a beta-voltaic cell could not capture the energy. This becomes nothing but a radioisotope heater, so the heat would have to be utilized like any other RTG.

Forum discussion
PeriodicTable.com
WebElements.com

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#106 2017-11-21 10:22:53

kbd512
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Registered: 2015-01-02
Posts: 1,187

Re: Land propulsion - Tracks, or tires?

People obsess over the heat energy that a radioisotope can produce and fail to consider the magnetic energy that the material generates, which is orders of magnitude greater.  Thermal conversion processes are inherently inefficient and even though recent developments are promising, they'll still fall far short of making an alpha or beta power cell a practical device for a vehicle.

Beta Radiation in a Magnetic Field

This is a very simple and well-known effect.  The principles for using it may not be widely known, but they're well understood by electrical engineers and aren't unique to radioactive materials.  The radioactive materials simply provide a current source using ionizing radiation.

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#107 2017-11-21 16:44:30

JoshNH4H
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Registered: 2007-07-15
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Re: Land propulsion - Tracks, or tires?

The problem with beta voltaics is that in a solid material the electrons tend to bounce around and have most of their energy converted into heat anyway. 

One thing I've always wondered about is the potential for preventing K-capture decays by stripping these isotopes of their electrons entirely and storing them in a vacuum chamber.  Wikipedia mentions that things of this sort may happen in nature (although it doesn't cite that claim so it's not very credible), but it does cite that Be-7 (decays by K-capture with a half life of 53 days) may have its half life affected with the presence of an insulating/conductive matrix.

I was originally thinking about this in the context of rocket propulsion.  Basically you'd have an electrostatic or magnetic cage full of stripped ions which you would introduce (micrograms at a time) into your combustion chamber.  When they mix with the normal matter in the combustion chamber (let's say water) they would steal a few electrons and decay rapidly, releasing huge amounts of heat (relative to chemical fuels) in the process.

There are three major problems with this idea that make it probably impossible, even in theory: Isotope selection, isotope production, and isotope storage.

For this to work, you need a combination of properties that are sort of contradictory.  You need an isotope whose decay energy is low (because any isotope with a decay energy above 1.022 MeV will also decay via positron emission) but decays quickly (ideally on the order of milliseconds).  The best you can do with K-capture is half-lives on the order of a few seconds, although I don't remember offhand which ones were best.  I want to say isotopes of Chlorine and Argon were my top two, and they had half-lives of a few seconds (which would be a pretty long residence time for propellant in a fuel chamber).

Once you've selected an isotope, production is a big issue too.  Isotopes that decay via K-capture are universally lighter than stable isotopes of the same element.  We don't have a good way of reliably producing this kind of isotope, especially in an electron-free environment.  You might try bombarding isotopes with high-speed protons, but that's not a selective process and probably 99.9% of the protons (or more!) will end up wasted.  That's not necessarily a problem if you're looking at a rocket launch but it's certainly not desirable.

There's also the problem of storage: As it turns out, it's really hard to strip heavy ions of all their electrons.  The energy involved is comparable to and maybe larger than the actual decay energy.  With such high energy potentials it can be really, really hard to keep electrons from jumping over virtually any potential barrier (especially with quantum tunneling).  Again, I haven't done the calculations but the magnitudes involved are way beyond even the physical limits of what we can do right now.

Some of these aren't as bad if you're storing energy for transportation (half-life is less important, for example, and something on the order of hours would be totally fine), but others are much worse (if you're losing 99.9%+ of your input energy, you might consider just using a battery).

Lastly,

RobertDyck wrote:

The interesting thing about this isotope [K-40] is it's sensitive to a modulated magnetic field. Properly modulated, the magnetic field causes the atoms to decay much faster. This is something science said shouldn't happen, but it does. Traditional science believes nothing changes the rate of decay of any isotope, but this one can be affected. That means you can cause rapid release of energy when you need it, turn it off when you don't. And beta radiation is so weak it can be blocked by a single sheet of paper, or a single layer of plastic film. A beta-voltaic cell works on the same principle as photovoltaic, but obviously uses beta radiation instead. Potassium-40 will be consumed as you produce energy, it will have a limited range, but the range should be much greater than chemical fuel.

Seeing as this does in fact defy just about everything we know about radioactive decay, I am extremely skeptical of this claim unless you can provide some rock solid evidence that this is actually true.  There were similar claims that X-ray bombardment could cause the expedited decay of metastable radioactive isotopes, but further experiments showed that this is in fact not true.


-Josh

If you try to talk to me about cold fusion or propellantless drives I will ignore you.
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#108 2017-11-21 17:14:20

Terraformer
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From: Lancashire
Registered: 2007-08-27
Posts: 2,508
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Re: Land propulsion - Tracks, or tires?

Roberts mention of K-40 reminded me of my suggestion to bombard Ca-40 with neutrons to produce Ca-41, which would then decay and release energy. But I don't think the cross section would be good enough, even if you could produce neutrons cheaply (a D-D fusor set up specifically for  that purpose?). Of course, if you had a cheap way of producing a fuel with a suitable half life and energy production rate, you could use it for power generation until you're ready to launch, and then switch to a thermal rocket for launch, then plug it back in on orbit to add to a massive power station...


"I guarantee you that at some point, everything's going to go south on you, and you're going to say, 'This is it, this is how I end.' Now you can either accept that, or you can get to work." - Mark Watney

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#109 2017-11-21 21:37:27

JoshNH4H
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Registered: 2007-07-15
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Re: Land propulsion - Tracks, or tires?

Producing neutrons with a low energy input is a tough one that I've been kicking around for a long time.  The neutron production problem is what killed NILFiR in the end, I just couldn't come up with a way to get neutrons for less than the 16 MeV energy of reaction


-Josh

If you try to talk to me about cold fusion or propellantless drives I will ignore you.
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#110 2017-11-22 04:08:12

elderflower
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Registered: 2016-06-19
Posts: 558

Re: Land propulsion - Tracks, or tires?

D/T fusion produces neutrons, helium and a huge amount of energy.

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#111 2017-11-22 07:31:38

JoshNH4H
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From: New York, NY, USA, Earth, Sol
Registered: 2007-07-15
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Re: Land propulsion - Tracks, or tires?

In theory it produces a large amount of energy, but in practice every device so far has actually produced a negative amount of energy at fantastic cost


-Josh

If you try to talk to me about cold fusion or propellantless drives I will ignore you.
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#112 2017-11-22 08:52:28

elderflower
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Registered: 2016-06-19
Posts: 558

Re: Land propulsion - Tracks, or tires?

Hydrogen weapons use this reaction. They produce huge amounts of energy. the problems arise from the need to contain and sustain the reaction. In twenty years time.....

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#113 2017-11-22 10:16:08

JoshNH4H
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From: New York, NY, USA, Earth, Sol
Registered: 2007-07-15
Posts: 2,193
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Re: Land propulsion - Tracks, or tires?

I've got some pretty strong opinions on fusion power that maybe aren't appropriate for this thread.  I'm either going to start a new thread or dig up an old one and explain them there.


-Josh

If you try to talk to me about cold fusion or propellantless drives I will ignore you.
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#114 2017-11-22 14:47:45

JoshNH4H
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From: New York, NY, USA, Earth, Sol
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Re: Land propulsion - Tracks, or tires?

Fusion post here


-Josh

If you try to talk to me about cold fusion or propellantless drives I will ignore you.
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