However, I find some assumptions suspect. Unlike rockets, donkeys can consume fuel en-route by grazing. Armies can also consume fuel by hunting, plundering and being "quartered" by their own people. You can make "supply trains" by having small groups of military gather such resources from a closer distance.
This is probably fairly accurate for camels and distances in the Saharan desert though, and you'd have to add the weight of water as well!
The original blog goes into a lot more detail, including the mechanics, logistics and risks of foraging.
The solution to getting around the wagon equation is ships, ships could carry tremendous amounts of food, with a minimal crew and thus minimum consumption, only problem is ships are expensive.
On donkeys, typically armies used mules and draft horses instead of donkeys, because of behavioral and maximum load reasons, and grazing is not enough for mules and large horses, also on certain seasons there is not enough grass for animals to graze in the terrain either.
The original blog has also a piece on nomad logistics, who used significantly smaller horses that can be sustained only by grazing, these armies were able to traverse a lot larger distances, hence the success of the mongol armies.
Well not the only problem, there's also the fact ships are limited to water deep enough to carry them, so you can't go too far from the coast or navigable rivers. Granted, in Europe, there are lots of navigable rivers that make waterborne logistics fairly simple if you have the boats. Ask the Vikings.
This is mitigated by the fact that rivers are attractive places to live, so the odds that a target of conquest is on a navigable river are fairly high.
Gets pretty bleak if this isn't true, and if your foe doesn't have to stay put, much worse. The Chinese tried to scour the horse barbarians of the hinterlands a few times. Didn't go well.
- grazing costs time, which increases the total amount of food that must be carried
- foraging equally costs time, so foraging more means a slower moving army
- but an army can only forage as it passes through terrain, so you need to keep moving, otherwise your army will eat the area into starvation, then die
It’s not quite that simple. Horses can eat much faster than they can digest so a few short breaks can represent a lot of food over a day. Further, horses eat significantly more than people. A 30% slower pace that requires 40% less food per day is a net win on distance but not time.
The main issue, is that the horses of agricultural societies are bred to a large size, and cannot survive by grazing alone, they need to have grains in their diet.
That’s false. Horses doing heavy work can’t survive on grazing alone, but they are perfectly fine when left alone in good pasture. Thus the phrase “put out to pasture,” old animals where often given something of a retirement where they where left to take care of themselves rather than simply be killed.
I don’t know that much about horses but it’s something like:
A normal horse left to graze in good pasture can get a calorie surplus per hour. That same horse doing work has a calorie deficit per hour based on how strenuous the labor. A horse can get into a maximum calorie debt before issues happen. Thus a few day of hard labor plowing a field isn’t an issue by its self and having redundant horses is useful.
In terms of the Wagon equation, taking a nearly empty wagon back is vastly less strenuous than taking a full one out. It may be that taking several times as long to get back significantly extends the total distance you can move the army from your base. It may also be that running a calorie deficit on the outbound trip and then grazing for days before the return trip is useful. But I doubt any army is would actually try and approach any kind of theoretical maximum as in practice flexibility is needed.
Granted that’s for the average horse, where extreme athletic performance means significant extra muscle mass and thus higher caloric needs independent of actual work being done. But the extreme athletic horses are expensive to maintain so likely used by messengers etc not wagons or farmers.
ha, most (historical) armies hope to gain lots of plunder as a result of their campaigns. According to Byzantine military doctrine, attacking a successful invader as they are leaving, burdened by all their booty, is one of the most advantageous times to strike.
The wagon equation isn’t only about armies, it’s about the logistics of moving things by wagon. Militaries need supplies to move with the army which adds a whole new set of constraints.
I agree it’s not that big a deal when moving a full wagon.
However moving a nearly empty wagon is vastly less effort for the horses. Using a historic example, the Huns they could move their army without needing to provide any food for their horses because each horse was doing so little work.
Foraging require enough of density of settlements en route. Cause that is what foraging is, taking food from locals by force. The bigger the army, the more and bigger settlements you need to burn and steal from.
>... animals where often ... retirement where they where left ...
The word you are looking for is "were"[1], specifically the first and third instances of "where".
I usually don't bother to be a grammar nazi, but I'm sorry: When you use the word "where"[2] and then also misspell "were" as "where" immediately before and after, things get really confusing really quickly.
Humans are more resilient than we give them credit for. Compared to other mammals we have a lot of coping mechanisms for injuries that are missing from other species.
There's a comedian who does a bit about how humans might be the bad guy in horror movies made by aliens, because we can scar in situations that would kill other animals, and we can run in intervals for far longer than most other mammals. We used them down, and that's probably part of our collaboration with dogs. We're all basically Michael Myers. We just keep coming, and as soon as you stop to rest, bam, there we are again.
Point is, hoofed animals tend to get injured in ways that will ultimately kill them. At that point if you have a butcher handy, you can be both humane and efficient, without necessarily being in a starvation situation. We talk about agriculture being a pivot point in human development but nobody ever seems to talk much about the power of soup.
> There's a comedian who does a bit about how humans might be the bad guy in horror movies made by aliens, because we can scar in situations that would kill other animals, and we can run in intervals for far longer than most other mammals.
I tried to find this skit but couldn't! Any more hints?
> examples? Humans aren't exactly resilient or fast healers in my mind.
Presumably they were referring to horses (and possibly donkeys?) having to be euthanized after a broken leg. Which is so well known, even "the Far Side" got in on the action[1].
I don't know what the OP has in mind, but if you break an ankle, you can splint it and hobble until it heals. If a large animal breaks an ankle, it's not going to heal.
I believe this was the 'official' strategy of some early arctic / antarctic expeditions. Kill the sledge dogs and feed them to the other dogs plus humans.
Well that was a strategy indeed but it can only go so far, additionally the same logistics apply to the food you place in the cache, you have to transport it there, the meat of the original article was, that really you are constrained in your movement by the terrains agricultural output, in high production terrain, your population and the enemies population as well will stockpile food for themselves that the army can draw upon, in places where the terrain is not suitable for high intensity agriculture the food available is much less and an army would quickly find itself exhausting all the stockpiles, in a matter of weeks, armies eat a lot of food.
Stationary fuel tanks seem problematic for rockets since your rendezvous would have to happen at such high speeds. You'd either have to decelerate the rocket back to zero or accelerate the fuel to the speed of the rocket.
Remember that all motion is relative. You can’t model space travel as simply going from point to point. Instead, you transfer from orbit to orbit and have to match velocities wherever you go. Relative to the propellant depot you have to reach zero velocity, but the propellant depot will be orbiting something at a very high speed just like you are.
You will likely have to go out of your way somewhat to reach a propellant depot, so you don’t want your propellant depots at the bottom of heavy gravity wells or in hard-to-reach orbits. But it’s still a viable strategy.
There are some places that your relative velocity with a propellant depot may be near zero already.
Natural staging points are not stationary, but they may be in fixed orbits, such as LEO (of a certain altitude, inclination), maybe a halo orbit of a Lagrange point (NASA’s Gateway is in NHRO, which is similar), or a highly Elliptical orbit near escape velocity. And you can do this for Mars as well.
By refilling at these staging points, you can chop up the rocket equation so you don’t get hit hard by the exponential. You have to get fuel there in the first place, and to do that you can use slower, more efficient trajectories or solar-electric propulsion (much higher Isp but slower) or in situ propellant production. You can also have better cooling at these staging points, taking a mass penalty off your crewed vehicle and offloaded to the depot in the case of cryogenic propellants that may boil off over time without an active chiller.
Propellant depots are a pretty powerful tool for expanding capability for space exploration. NASA picked SpaceX’s Starship as the lander for their Artemis lunar missions, and that will fuel up using a depot in Earth orbit.
However, I find some assumptions suspect. Unlike rockets, donkeys can consume fuel en-route by grazing. Armies can also consume fuel by hunting, plundering and being "quartered" by their own people. You can make "supply trains" by having small groups of military gather such resources from a closer distance.
This is probably fairly accurate for camels and distances in the Saharan desert though, and you'd have to add the weight of water as well!