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Let's say that there's a group of humans walking across a plain.

Incredibly strong winds blow across this plain at predictable intervals on an hourly basis.

For one hour, the wind magically blows in from behind the travelers, pushing in the direction they're traveling - so much, in fact, that they need to wear weighted packs on their backs in order to pull themselves backwards and stop themselves from tipping over.

The next hour, the wind dies to absolutely nothing. Zero. Nada. Zilch.

The next hour, the wind magically blows in from in front of the travelers, pushing away from the direction they're traveling. Again, they need to wear weighted packs in order to stop themselves from tipping over; however, in this case, they have to be on their front, in order to lean them forwards into a wind that's trying to push them backwards.

The next hour, the wind dies again, and the cycle repeats from the beginning.

Hunkering down during the windy hours and moving during the clear ones is not doable for a couple of reasons that are irrelevant within the scope of this question, as is splitting the group up. This means that they have to carry the packs constantly, rather than ditching them.

Assume that they magically have infinite endurance (not strength, endurance; they can't carry infinite weight, but they can carry some weight forever), don't need to sleep, etc.

Question: how heavy of a backpack can the average human wear on their front or back while still maintaining a walking pace and not tripping/falling over/etc?

Let's say that they're wearing a high-quality hiking backpack that transfers most weight to their hips.

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  • $\begingroup$ All depends on how this weight is positioned with relation to wearer's body. Good backpacks transfer load to wearer's hips, bad backpacks don't even transfer it well to the shoulders. $\endgroup$
    – Alexander
    Aug 28, 2021 at 2:26
  • $\begingroup$ @Alexander True, but I'm really not sure how to quantify that. I'll edit it, though, if it improves clarity. $\endgroup$
    – KEY_ABRADE
    Aug 28, 2021 at 2:30
  • $\begingroup$ With a good backpack and high load, wearer's legs would gave out first before tripping (this isn't to say that you can't fall forward or backward). $\endgroup$
    – Alexander
    Aug 28, 2021 at 2:36
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    $\begingroup$ I would think walking sticks of some kind would be a better option than extremely heavy packs (at least in the wind-from-behind scenario). $\endgroup$ Aug 28, 2021 at 7:18
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    $\begingroup$ weighing a heavy backpack will not rally help, the pack is still above the center of gravity so it only helps destabilize the person. $\endgroup$
    – John
    Aug 28, 2021 at 13:48

5 Answers 5

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Frame challenge: A heavy backpack isn't the right tool

On long duration hiking trips, every extra gram of load is meticulously considered. I personally know a guy who cuts down his hiking toothbrushes to half size to avoid the extra weight. Additionally, these people are presumably going to be carrying water and food with them, which are used up as they go, resulting in lighter packs. Are they going to carry their excrement with them? Not likely. Even less likely would be requiring people to carry useless weights.

Specific to this windy situation though, I don't really think it makes sense to continue onwards when facing a headwind of dangerous speeds. All you'd be doing is tiring out the travelers, crossing less distance, and risking injury from the ground debris/insects/whatever which will doubtlessly be flung at the travelers. Also, when they have a tailwind, that's free energy!

I think there are several clever options your travelers could use:

Land sailing vehicles

The earliest records of people putting wheeled sailing vessels on land date back to ~500AD, but they've been used occasionally ever since. A notably relevant example would be that these vehicles, called "windwagons" were also used by American settlers crossing the Great Plains:

Windwagon

They can also be built quite large, as seen in this example:

Large Windwagon

With such a vehicle, the group of travelers could make progress at all times:

  1. During periods of tailwind, they all sit in the wagon and zoom across the plains
  2. During periods of stillness, they all get out and pull the wagon, since they are well rested (or they can just sit around and wait for the wind to pick up again)
  3. During periods of headwind, they tack against the wind and still make considerable progress

Kites

Each traveler carries a small kite that is proportioned to their body size. It is easy to repair and disassembleable when necessary. Additionally, they have a harness on their body which allows them to tie the kite's rope to their center of mass. Then, they simply:

  1. During periods of tailwind, they launch their kites and attach the ropes to their harnesses. The force of the wind on the kite counters their weight almost perfectly, and like windsurfer astronauts, they take enormous floating steps forwards covering tens of meters with each stride. This isn't exactly without risk, but because the winds are so constant and predictable, it's still rather safe.
  2. During periods of stillness, they simply carry their kites with them and move at a rapid pace/jog for an hour.
  3. During periods of headwind they hunker down, rest, and to avoid being blown away, they hammer ropes connected to their harnesses into the ground with pitons.
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    $\begingroup$ I like this answer! Kite... or sail? I'm not sure you need the structure of a kite, just a sail may be enough, and it'll be lighter. $\endgroup$ Aug 28, 2021 at 15:57
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Your "tipping point" happens when the wind basically pulls your center of gravity outside of the area of support between your feet. That is highly dependent on the size of the people, their surface area and the windspeed.

I myself have once been in such a gale wind that I had to lean forwards, but each time I tried to take a step my foot was simply blown backwards, I did not have the strength and leverage to put it in front of me. To my surprise I had leaned so far forwards that my hands could reach the ground in front of me, so without leaning on my arms I used my hands to pull myself forwards. I had no packs, so theoretically your travelers could do something similar. Going the other way all I had to do was lean against the wind and lift my foot, then put it down as the wind would push it forwards.

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    $\begingroup$ I can confirm I had something similar happen in the Wyoming plains, walking sticks and cleats to keep your footing can be a huge help but a heavy pack just makes the hike harder. $\endgroup$
    – John
    Aug 28, 2021 at 13:50
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    $\begingroup$ This. The limit is going to be when you lose traction. $\endgroup$ Aug 29, 2021 at 2:36
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30-35 kg, but it won't help (much)

First, a big caveat - I have no idea what "the average human" is like. Is it the mean of all humans alive today, including newborn babies and adults with infirmities that don't allow them to walk? Is it the median of all those that can walk? Note that just the word "average" has multiple meanings in statistics.

Hence, my answer is based on the standard "marching order" loadout for Australian infantry soldiers from 20ish years ago. Not everyone's load would be equal, depending on exact weapons and equipment, but generally it worked out to 30-35 kg per person. Not all of it was on the back, but if you had to strap your weapon to your pack then it was still able to be carried. Adding much more weight (eg "how about you carry the 84mm Carl Gustav too") had a significant effect on performance, so going much above that is a problem.

Similarly, when you had to get on certain military aircraft for short flights on the lovely inward-facing seating then pack, webbing etc was all carried on the front of the body and was on your lap for the duration of the flight. The awkwardness of carrying the load on the front was more due to the height of the pack blocking vision rather than the weight.

However, now that I've breezily asserted the weight (OK, kg are mass, the weight is approximately 300-350 N for those being pedantic about units) I'll mention why adding weight to the front or back isn't going to help. As mentioned by @SonorelHaetir in comments, a good pair of walking sticks will be much more help. You do not want to be standing up as straight as possible in a wind that high, you want to lean forward and reduce your cross-section. With a tail wind you can make up time by jogging with greatly reduced effort even uphill if not heavily laden. Given that the question makes it mandatory to keep moving during the strong headwind, leaning forward and using sticks or other handholds to keep moving forward is the way to go. Regardless of whether the wind is in front, behind or nil, increased weight will decrease speed for a person of a given strength.

The above assertions are based on near-daily commutes either cycling or (mostly) running across a >1 km bridge where some genius civil engineer decided to create really narrow pedestrian walkways (just wider than the handlebars of a single mountain bike!) elevated above the roadway and fully exposed to the winds from all directions. The trick is always leaning into headwinds or crosswinds, using the railings as handholds in extreme conditions (in place of walking sticks that would skid off the surface). On the rare occasions where there is a favourable tailwind it is possible to run almost effortlessly.

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    $\begingroup$ US solders humped "over 160 pounds" (72kg) in Grenada. +1 for starting with a unit of weight. $\endgroup$
    – Mazura
    Aug 28, 2021 at 21:34
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Weight might be helpful but your wind catching surface area might be just if not more important. That said I'm not sure "tipping over" would be the main issues. More likely its how much energy you need to expend to travel.

This video demonstrates just how tiring it will be just to stand let alone walk. https://www.youtube.com/watch?v=O4pFdLJmG7M&ab_channel=NBCNews If you did want to add weight you would want it as low and compact as you can get it. Though adding weight will also take energy to move so it might not really help.

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  1. Maybe they could crawl along the plain when the wind is blowing strongly from ahead, behind, or the sides. Making themselves lower will reduce the surface that the wind can push against.

    For a heavily travelled route trenches could be dug to keep travellors below the level of the wind.

  2. Maybe they can build special types of small man-powered wagons for carrying their stuff. The wagons would be built low to the ground and their loads would also be piled low to the ground and tightly secured so they don't blow away.

    The person would stand in an open space in the center of the wagon, and would attach their harness to the wagaon at several places. Possibly there could be vertical poles up to shoulder height at the four corners of the wagon, and some of the harness would go from the corners to the shoulders of the person. Thus when the wind blew the person toward one the poles, and that line went a little slack, the opposite line would be pulled fight, preventng them from moving much.

    So the weight of the wagon and the attachment system would keep the person from being blown over by the wind.

  3. Maybe there are rest stops and shelters each hour's journey across the plain, where the travelers can stop whenever the wind is blowing, or at least whenever it is blowing against their direction of travel.

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