It fascinates me that it's an exponential function—the engine that transports fuel, and consumes fuel proportional to distance traveled: its fuel cost grows exponentially. The precise laws of physics work out, just barely, that we can send fuel around the world by boat; or, as here, by airplane to a near-antipode of the world. It's physically possible to circumnavigate the world either way.
It'd only take a slight modification of several physical constants that planets would be too large to cross. An alternate universe with continents so vast, no machine, no amount of fuel, could allow any exploration of their deepest interior; secrets permanently concealed.
Pipelines solve this problem quite neatly. The transport cost of a pipeline is very small compared to the fuel transported.
Interestingly pipelines can have near perfect fuel efficiency (though few do) since it's possible to run the pumps with electricity. That means if the electricity that ran the pumps came from wind or solar no fuel was burned to move the product.
At this point in time the only other thing that might be able to work that way is electrified freight trains. I don't believe there are any here in the US, at least not significant distances.
Look up US coaling stations as well. The Great White Fleet (circumnavigated the globe from 16 Dec. 1907 to 22 Feb 1909) was a demonstration that the US could send 16 battleships and support vessels on global missions.
Transition of navies from coal to oil (initiated by the British just prior to WWI) greatly simplified bunkering operations. Fuel was still required, but oil (even the extraordinarily viscous bunker oil used by ships) is far easier to manage both in fueling and subsequent rebunkering to maintain ship's trim than solid coal.
Among significant US refueling stations was the Saudi peninsula (though precisely where I'm not certain), which had a strong influence on subsequent US relationships and allegiances in the region, particularly notable after the discovery of vast oil reserves.
I'd be interested in a list of US coaling / fueling stations, though I'm not finding one immediately. Pearl Harbor (Hawaii) and Subic Bay (Philippines) / were all but certainly two of these.
That's the famous rocket equation (and with rockets, none of the solutions other replies mention, like depots or pipelines, are available). There's a thought experiment that for a planet only a bit heavier than Earth (something like 2x or 5x) it might be completely impractical to launch anything into orbit.
Long before there was the tyranny of the rocket equation, there was also the tyranny of the wagon equation [1] that limited how far per-industrialized armies could move with wagons and animals (though the equation wasn't formalized).
Logisticians were intimately aware of the concept but I’ve never seen an equation formally written down or mentioned anywhere in ancient or medieval texts. They would have used a simplified version for planning - counting days of food an army has and how far they can move from their bases on that food, plus how much they can forage for and how much they can take from the local population.
It looks more like a Civ5 game board than a neat equation like the ideal rocket equation.
Breguet range equation for airplanes also predates rocketry though postdates wagons. Airplanes can already have a significant portion of their weight as fuel. It has a logarithm of the mass ratio as one of the terms.
And by "significant", half or more their take-off weight.
Boeing B-52 Stratofortress: dry weight 38.25 tonne, fuel capacity 141.6 tonne, ratio 3.7:1. Max takeoff weight: 221.3 tonne. If at max fuel, that's 63% fuel. In practice, this aircraft refuels, often multiple times, on missions, which may span the globe.
Boeing 747-8: dry weight 220 tonne, fuel capacity 238.6 tonne, ratio 1.08:1. Max takeoff weight: 447.1 tonne. If at max fuel, that's 53% fuel.
Much of the fuel burn is on take-off and climb, meaning that cruise portions of flight are already at significantly less than take-off weight, and further reduce with time. You'll occasionally see long-distance flight profiles in which the altitude of the aircraft increases over the flight (in 1,000 ft increments given air traffic regulations) as fuel load decreases and maximum efficient altitude increases.
A planet's mass doesn't matter so much as the density. If you look at a planet like Saturn, it is almost 100x heavier, but it's surface gravity is nearly identical to Earth's. What really matters for rockets though is the surface escape velocity, which scales like the square root of mass divided by radius. So for large radii it is slightly worse than density, which scales like mass divided by radius cubed. Ideally you would live on a small rocky planet (Mars ftw).
I tried to calculate a formula once, to convert increment of Earth's mass to increment of Earth's gravity for a planet of the same density, so not the same as escape velocity but sort of related. I'm not sure if it's actually correct but it was: x/x^(2/3) So i.e. for 5 Earth masses and the same density, it would be 1.71 of Earth's gravity on the surface, 10 masses -> 2.15 Earth's gravity.
Reasoning: Acceleration is GM/R^2 and planets R is like (x * Me / 4Pi / density)^1/3 . Directly proportional to M and inverse square root of radius, while the radius is directly proportional to (x)^(1/3)
Though the density for 2 planets made of the same stuff and different masses would probably be different due to differences in pressure in its internals? Just a guess.
In one of his books (I believe it's Collapse though possibly Guns, Germs, and Steel, Jared Diamond comments on how introduction of novel foodstuffs, in particular the potato or sweet potato, by Europeans, greatly changed military capabilities and hence power relations amongst indigenous Pacific islanders. Particularly in New Zealand if memory serves.
I'd had to be careful in noting that these were foods introduced by Europeans, but not European foods of themselves, in that potatoes (both varieties) are native to the Americas.
Surprised its a piston not a turbine, but I guess piston tolerances are lower and so can be maintained more easily on site. But you would think a gas turbine was equally efficient and a good fit. Plus, it's standard to ship them worldwide, they're understood pretty well as movable commodities.
Ostensibly, the Abrams turbine can use a wider range of fuels, including diesel, gasoline and jet fuel, and provides more power for less weight to get higher mobility and agility in the field. Those are some pretty compelling advantages when your life depends on it, if they actually do that and don't break down every other day.
Without enough personal experience to compare, though, I can't say that I'd be surprised either way.
They would use electricity from the grid, why bother generating power specifically for the base? Outsource the capital and maintenance costs to a utility.
Some land-grant universities generate their own power and some industrial sites have their own dedicated hydropower, but a military base would just use the grid.
For critical/backup power needs at the base itself, a combination of UPSes and diesel generators, just like any other commercial or industrial facility. Diesel gensets are an extremely mature, well understood technology that are very reliable and cheap to maintain.
My guess is that repairs for piston based generators can be fabricated on site in the machine shop whereas repairs for turbine based generators probably require a bit more tooling than they have access to.
Important given that the site has no access in or out for roughly 8 months out of the year.
Yeah. This was part of the issue that nukey-poo had at mcmurdo back in the 70s.
It's not nearly as bad now due to improvements in electronics, nuke tech, and automation, but turns out running a nuclear reactor takes a lot of highly skilled (and expensive) people. Of course nukey-poo was staffed by like 30 seabees working full time so staffing was a bit less of an issue but that's still a very expensive proposition.
There's talk from the biden admin of the military adopting SMRs (small modular reactors) again now that they are so much cheaper, simpler, better contained, and less staff intensive to operate. So it'd be interesting to see if they offer support for one to the USAP to use at the pole.
Of course that comes with it's own added problems (potential interference with science experiments like icecube) given that they spew neutrinos with basically no ability to shield them. So if they were to do it, they'd probably have to install it quite a ways away from the dark sector.
Besides easier maintenance, a piston motor may have better energy efficiency.
The big two-stroke Diesel engines, like those used on ships, have energy efficiencies over 50%, e.g. around 55%.
I do not know if there have been some recent improvements in gas turbines, but at least a few years ago the efficiency of gas turbines was lower, sometimes as low as 40%. The reason is that the exhaust gases of a gas turbine are very hot, retaining inside a significant fraction of energy from the consumed fuel.
Electrical turbogenerators are preferred for mobile or military applications due to much smaller sizes for a given power and higher reliability, not because of good efficiency.
In order to have good efficiency when using a gas turbine, one must recover the heat from the exhaust gases, like in all combined-cycle power plants, where high efficiencies, e.g. over 65%, are attained by using a cascade of steam turbines, typically 3 steam turbines, for heat recovery. This increases a lot the size of the power plant and it requires a lot of water, which in Antarctica could be obtained only by melting ice, reducing the efficiency gains and complicating a lot the power plant (a special construction would be necessary to prevent water freezing in undesirable places and to use the water in closed cycle, otherwise the energy efficiency of a combined cycle starting from ice may be less than of a simple gas turbine).
A more realistic solution for using a gas turbine in Antarctica would be to recover the heat from the gas turbine that burns fuel with a closed-cycle gas turbine using supercritical carbon dioxide. While this is a promising method for replacing the entire cascade of steam turbines (with steam turbines, you need a cascade because heat is exchanged at fixed temperatures, where water is boiling; while with a supercritical fluid heat can be exchanged at a continuously decreasing temperature of the exhaust gases, recovering most of the waste heat in a single heat exchanger), it was mostly experimental and I do not know if there are any suitable commercial products at this time.
A piston engine can last a generation. You might get a year out of a turbine engine.
Every week I hook up to a military vehicle (HEMTTA4) that was built in 1984, with a CAT diesel engine. Absolutely flawless.
Besides, a turbine engine has two modes: ridiculous and ludicrous. I can idle a diesel engine for days on the fuel it takes to fire up and run a turbine engine for a short period.
Small generating turbines are almost always natural gas. For logistics purposes, the Antarctic program uses only aviation fuel, which is very diesel-ish, and for diesel piston engines are the rule.
If you really wanted, I suppose, you could get a liquid fuel turbine, but it would be military or aviation, and much rarer than what they have. And they need to have things as simple as possible, given their staffing constraints.
Also, they seem to like several smaller gensets, to allow for problems and maintenance, which leads to relatively small generators. (They're 750kW ea.) Turbines aren't really common that small. They mostly want to start at several MW.
Jet aviation fuel is typically kerosene, which has an average carbon chain length of about 10, as compared to diesel which ranges from 12 to 15.
Among critical factors, diesel fuel freezes at far higher temperatures than kerosene, which is important for both aircraft (which typically fly in ambient temperatures about -40 °F/°C) and polar operations. Blends such as Jet A1 and Jet B (kerosene + petrol) have still lower freezing points of -47 °C and -60 °C respectively.
Diesel's freezing temperatures are ~ - 8--9 °C / 15--17 °F. Kerosene and jet aviation fuel are rated to -40 °C / -40 °F (both temperature scales are the same at this temperature).
Piston aircraft burn petrol / gasoline with a freezing point of ~ -73 °C / -100 °F.
Shorter hydrocarbon chain lengths -> lower freezing temperatures. Methane (CH4) is liquid to -182 °C / -195 °F, and only liquifies at -162 °C / -259 °F.
The McMurdo reactor had so many problems, they shut it down prematurely and switched back to diesel generators, because that was cheaper and more reliable. Nuclear power is great for environmentally safe regions with large populations, but it sucks in remote areas with little infrastructure and no support.
34 comments
[ 4.4 ms ] story [ 83.4 ms ] threadIt'd only take a slight modification of several physical constants that planets would be too large to cross. An alternate universe with continents so vast, no machine, no amount of fuel, could allow any exploration of their deepest interior; secrets permanently concealed.
Interestingly pipelines can have near perfect fuel efficiency (though few do) since it's possible to run the pumps with electricity. That means if the electricity that ran the pumps came from wind or solar no fuel was burned to move the product.
At this point in time the only other thing that might be able to work that way is electrified freight trains. I don't believe there are any here in the US, at least not significant distances.
Aden
Bahamas
Bermuda
Bombay
Gibraltar
Halifax
Hong Kong
Jamaica
Malta
Singapore
Suez
Trincomalee
A: They are all former coaling stations in the British Empire
Transition of navies from coal to oil (initiated by the British just prior to WWI) greatly simplified bunkering operations. Fuel was still required, but oil (even the extraordinarily viscous bunker oil used by ships) is far easier to manage both in fueling and subsequent rebunkering to maintain ship's trim than solid coal.
Among significant US refueling stations was the Saudi peninsula (though precisely where I'm not certain), which had a strong influence on subsequent US relationships and allegiances in the region, particularly notable after the discovery of vast oil reserves.
I'd be interested in a list of US coaling / fueling stations, though I'm not finding one immediately. Pearl Harbor (Hawaii) and Subic Bay (Philippines) / were all but certainly two of these.
[1] https://maximumeffort.substack.com/p/the-tyranny-of-the-wago...
It looks more like a Civ5 game board than a neat equation like the ideal rocket equation.
Boeing B-52 Stratofortress: dry weight 38.25 tonne, fuel capacity 141.6 tonne, ratio 3.7:1. Max takeoff weight: 221.3 tonne. If at max fuel, that's 63% fuel. In practice, this aircraft refuels, often multiple times, on missions, which may span the globe.
Boeing 747-8: dry weight 220 tonne, fuel capacity 238.6 tonne, ratio 1.08:1. Max takeoff weight: 447.1 tonne. If at max fuel, that's 53% fuel.
Much of the fuel burn is on take-off and climb, meaning that cruise portions of flight are already at significantly less than take-off weight, and further reduce with time. You'll occasionally see long-distance flight profiles in which the altitude of the aircraft increases over the flight (in 1,000 ft increments given air traffic regulations) as fuel load decreases and maximum efficient altitude increases.
A planet's mass doesn't matter so much as the density. If you look at a planet like Saturn, it is almost 100x heavier, but it's surface gravity is nearly identical to Earth's. What really matters for rockets though is the surface escape velocity, which scales like the square root of mass divided by radius. So for large radii it is slightly worse than density, which scales like mass divided by radius cubed. Ideally you would live on a small rocky planet (Mars ftw).
Reasoning: Acceleration is GM/R^2 and planets R is like (x * Me / 4Pi / density)^1/3 . Directly proportional to M and inverse square root of radius, while the radius is directly proportional to (x)^(1/3)
Though the density for 2 planets made of the same stuff and different masses would probably be different due to differences in pressure in its internals? Just a guess.
I'd had to be careful in noting that these were foods introduced by Europeans, but not European foods of themselves, in that potatoes (both varieties) are native to the Americas.
I wouldn’t say I even come close to being and arm chair expert on this, I’m just curious if anyone else knows.
Nothing beats being able to make field repairs quickly and easily when crap hits the fan.
Abrams use a turbine for the weight to power output ratio, optimizing mobility rather than efficiency.
Without enough personal experience to compare, though, I can't say that I'd be surprised either way.
They would use electricity from the grid, why bother generating power specifically for the base? Outsource the capital and maintenance costs to a utility.
Some land-grant universities generate their own power and some industrial sites have their own dedicated hydropower, but a military base would just use the grid.
For critical/backup power needs at the base itself, a combination of UPSes and diesel generators, just like any other commercial or industrial facility. Diesel gensets are an extremely mature, well understood technology that are very reliable and cheap to maintain.
Important given that the site has no access in or out for roughly 8 months out of the year.
It's not nearly as bad now due to improvements in electronics, nuke tech, and automation, but turns out running a nuclear reactor takes a lot of highly skilled (and expensive) people. Of course nukey-poo was staffed by like 30 seabees working full time so staffing was a bit less of an issue but that's still a very expensive proposition.
There's talk from the biden admin of the military adopting SMRs (small modular reactors) again now that they are so much cheaper, simpler, better contained, and less staff intensive to operate. So it'd be interesting to see if they offer support for one to the USAP to use at the pole.
Of course that comes with it's own added problems (potential interference with science experiments like icecube) given that they spew neutrinos with basically no ability to shield them. So if they were to do it, they'd probably have to install it quite a ways away from the dark sector.
The big two-stroke Diesel engines, like those used on ships, have energy efficiencies over 50%, e.g. around 55%.
I do not know if there have been some recent improvements in gas turbines, but at least a few years ago the efficiency of gas turbines was lower, sometimes as low as 40%. The reason is that the exhaust gases of a gas turbine are very hot, retaining inside a significant fraction of energy from the consumed fuel.
Electrical turbogenerators are preferred for mobile or military applications due to much smaller sizes for a given power and higher reliability, not because of good efficiency.
In order to have good efficiency when using a gas turbine, one must recover the heat from the exhaust gases, like in all combined-cycle power plants, where high efficiencies, e.g. over 65%, are attained by using a cascade of steam turbines, typically 3 steam turbines, for heat recovery. This increases a lot the size of the power plant and it requires a lot of water, which in Antarctica could be obtained only by melting ice, reducing the efficiency gains and complicating a lot the power plant (a special construction would be necessary to prevent water freezing in undesirable places and to use the water in closed cycle, otherwise the energy efficiency of a combined cycle starting from ice may be less than of a simple gas turbine).
A more realistic solution for using a gas turbine in Antarctica would be to recover the heat from the gas turbine that burns fuel with a closed-cycle gas turbine using supercritical carbon dioxide. While this is a promising method for replacing the entire cascade of steam turbines (with steam turbines, you need a cascade because heat is exchanged at fixed temperatures, where water is boiling; while with a supercritical fluid heat can be exchanged at a continuously decreasing temperature of the exhaust gases, recovering most of the waste heat in a single heat exchanger), it was mostly experimental and I do not know if there are any suitable commercial products at this time.
Every week I hook up to a military vehicle (HEMTTA4) that was built in 1984, with a CAT diesel engine. Absolutely flawless.
Besides, a turbine engine has two modes: ridiculous and ludicrous. I can idle a diesel engine for days on the fuel it takes to fire up and run a turbine engine for a short period.
If you really wanted, I suppose, you could get a liquid fuel turbine, but it would be military or aviation, and much rarer than what they have. And they need to have things as simple as possible, given their staffing constraints.
Also, they seem to like several smaller gensets, to allow for problems and maintenance, which leads to relatively small generators. (They're 750kW ea.) Turbines aren't really common that small. They mostly want to start at several MW.
Among critical factors, diesel fuel freezes at far higher temperatures than kerosene, which is important for both aircraft (which typically fly in ambient temperatures about -40 °F/°C) and polar operations. Blends such as Jet A1 and Jet B (kerosene + petrol) have still lower freezing points of -47 °C and -60 °C respectively.
Diesel's freezing temperatures are ~ - 8--9 °C / 15--17 °F. Kerosene and jet aviation fuel are rated to -40 °C / -40 °F (both temperature scales are the same at this temperature).
Piston aircraft burn petrol / gasoline with a freezing point of ~ -73 °C / -100 °F.
Shorter hydrocarbon chain lengths -> lower freezing temperatures. Methane (CH4) is liquid to -182 °C / -195 °F, and only liquifies at -162 °C / -259 °F.
<https://www.amspecgroup.com/news/types-of-jet-fuel/>
I'm hopeful because the DoD plans a similar program like the PM-3A was to provide nuclear energy for military bases (project PELE)