Physical size of crew and space ship effectiveness

[Deebles]

I was pondering a small sci-fi based on a crew entirely consisting of individuals with achondroplasia, or other conditions that lead to having a short stature. The rough reasoning was that if a ship was built with a maximum crew height of, say, 4'8 in mind, and also a smaller mean crew body mass in mind, you'd need smaller crew spaces (which would be correspondingly easier to protect from radiation), smaller space suits, less food, less oxygen, less water, and thus the ship could devote more of its capacity to fulfilling its other functions in space. But has anyone actually done the maths on how much of a difference this would make?

Possible scenarios:
- A near future scenario of a ship designed around deviating the course of an incoming asteroid (gaining a pay-off of being able to carry a greater tonnage of stuff-to-deal-with-the-asteroid)
- A slightly further future scenario of a sleeper ship with a skeleton crew. (The sleepers being largely children, and the skeleton crew people with a shorter stature working on a rotating sleeper shift, to evacuate as many people from the solar system as possible with a ship that could reasonably keep them safe from radiation and the impact of collisions).
- A combat-orientated spaceship
- A modern-world custom-built (handwaving the ridiculous expense) combat aircraft of some kind.

[Deebles]

(All this, of course, would have to acknowledge that the saving would be much less than for an entirely automated/AI-piloted vessel in any of the scenarios given).

[madd0ct0r]

first thing I found. recommends a maintence diet of 1000-1400kcal

http://www.lpaonline.org/assets/documen ... Person.pdf

[Simon_Jester]

I"m not sure this'd pay off.

First of all (and I don't actually know if this is true, it just occurred to me) some of the conditions that lead to dwarfism may have secondary medical consequences. It's important that the crew of a military aircraft or a spacecraft be in good health, preferably very good health; astronauts are screened carefully for this reason.

Secondly, the savings aren't necessarily decisive unless the majority of the ship's mass is dedicated to life supporting systems. If you're hauling, say, 100 crewmen and 10000 corpsicles in cryogenic tanks, then the space dedicated to the crewmen is probably NOT the dominant factor setting the size of the ship.

Thirdly, the amount and quality of things like computer support and automated repair systems may do more to determine the viability of a ship on a long mission than the size of the crew. Even if you can replace 20 normal men with 20 midgets, it may prove more cost-effective to replace them with 10 men and a better set of computers and robots.

Now, I've seen the idea done before- The Space Merchants by Frederik Pohl and Cyril Kornbluth

[Deebles]

first thing I found. recommends a maintence diet of 1000-1400kcal

http://www.lpaonline.org/assets/documen ... Person.pdf

Half the nutritional requirements of a normally-sized person? That seems like it would come in very handy indeed.

I"m not sure this'd pay off.
First of all (and I don't actually know if this is true, it just occurred to me) some of the conditions that lead to dwarfism may have secondary medical consequences. It's important that the crew of a military aircraft or a spacecraft be in good health, preferably very good health; astronauts are screened carefully for this reason.

Indeed, those who had conditions with such secondary medical consequences would have to be screened out. But not all such conditions do - achondroplasia, for instance, which is one of the most common, isn't associated with anything that would preclude spaceflight to the best of my knowledge.

A more serious obstacle, to my mind, would be that we're limiting our recruitment pool to something in the range of 1 in 1,000 to 1 in 10,000 people. On top of all the other limits to who can go into space, there might well be a skills detriment.

Secondly, the savings aren't necessarily decisive unless the majority of the ship's mass is dedicated to life supporting systems. If you're hauling, say, 100 crewmen and 10000 corpsicles in cryogenic tanks, then the space dedicated to the crewmen is probably NOT the dominant factor setting the size of the ship.

Half the rations. Less oxygen. Less water. Less mass of clothing, spacesuits, and quarters. It has to add up.

Thirdly, the amount and quality of things like computer support and automated repair systems may do more to determine the viability of a ship on a long mission than the size of the crew. Even if you can replace 20 normal men with 20 midgets, it may prove more cost-effective to replace them with 10 men and a better set of computers and robots.

Indeed, automation can easily trump this as an effect. But at the same level of automation, you'll get greater efficiency with smaller people.

Now, I've seen the idea done before- The Space Merchants by Frederik Pohl and Cyril Kornbluth

Thanks! I should probably look that up

[Simon_Jester]

first thing I found. recommends a maintence diet of 1000-1400kcal

http://www.lpaonline.org/assets/documen ... Person.pdf

Half the nutritional requirements of a normally-sized person? That seems like it would come in very handy indeed.

Thing is, on a really long mission you're already committed to carrying some mechanism for growing your own food; it's not practical to just carry hundreds of cases of MREs. While this way your mechanism can be smaller, it will still be pretty substantial- especially if you hit diminishing returns when you try to downsize your hydroponic machinery too far.

Also, your midget crewmen will probably have to do a fair amount of mechanical labor and remain alert and healthy, which will increase their calorie intake until it's closer to what a larger person would need.

I"m not sure this'd pay off.
First of all (and I don't actually know if this is true, it just occurred to me) some of the conditions that lead to dwarfism may have secondary medical consequences. It's important that the crew of a military aircraft or a spacecraft be in good health, preferably very good health; astronauts are screened carefully for this reason.

Indeed, those who had conditions with such secondary medical consequences would have to be screened out. But not all such conditions do - achondroplasia, for instance, which is one of the most common, isn't associated with anything that would preclude spaceflight to the best of my knowledge.

A more serious obstacle, to my mind, would be that we're limiting our recruitment pool to something in the range of 1 in 1,000 to 1 in 10,000 people. On top of all the other limits to who can go into space, there might well be a skills detriment.

You are actually right, that's a bigger issue. There just aren't that many midgets with genius IQ and technical degrees out there. And if you're relying on midget crewmen to do things a non-genius can do, again you find it likely that a lot of the possible jobs for crewmen can be automated, in which case you might as well dispense with them entirely.

Secondly, the savings aren't necessarily decisive unless the majority of the ship's mass is dedicated to life supporting systems. If you're hauling, say, 100 crewmen and 10000 corpsicles in cryogenic tanks, then the space dedicated to the crewmen is probably NOT the dominant factor setting the size of the ship.

Half the rations. Less oxygen. Less water. Less mass of clothing, spacesuits, and quarters. It has to add up.

Yes, but add up to what?

Basically, when you remove something from a spacecraft to save weight, you have to consider what you give up in order to save weight. I mean, removing the fuel tanks saves lots of weight... but now your ship can't move.

So, we stop and think. Suppose that we're talking big ships- say, a 1000-ton habitat and life support module designed to support fifty crewmen more or less indefinitely (no idea if this is generous or stingy), plus twenty thousand tons of cargo bay, engines, and fuel tanks. Your ship masses 21000 tons.

Now, replace the crew with midgets. Every part of the habitat and life support systems is reduced in mass by about half. Now you have a 20500-ton ship. This is literally less than a 2.5% reduction in the ship's overall mass. This is not enough to noticeably affect performance.

BUT, in order to get this incremental "improvement," you had to either recruit every technically proficient midget on Earth. Or you had to accept much lower recruiting standards because the only available applicants are midgets.

Your ship will accelerate 2.5% faster, or carry maybe 5-10% more fuel or cargo. But in return it is crewed by people who are far less effective at their jobs. Or who can command massive, princely salaries due to being basically irreplaceable. Because where are you going to find a midget nuclear engineer if the one you have quits? Plus, the odds are good that the only midget nuclear engineer in the world is NOT the world's best nuclear engineer- just a pretty good one.

As long as there is no emergency, the crew of uninspired midgets will probably do an adequate job. But in case of an emergency where brains, resourcefulness, and familiarity with complex technical systems make the difference between life and death... you may end up very sorry you hired people for their height and not for how good they were at their jobs. Somehow I doubt that improving the ship's performance by 5% or whatever justifies that risk.
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Basically, the weight savings from filling your ship with midgets is only large and significant if your ship is almost all habitat compartments, in that virtually all the space not dedicated to engines and fuel tankage is dedicated to housing and storing live, walking, breathing people. Not scientific instruments, not cargo, not weapons, not cryo-suspended colonists. People.

I can't think of many applications for such a ship other than a passenger liner or a troop transport (in neither case can you cater exclusively to midgets).

Thirdly, the amount and quality of things like computer support and automated repair systems may do more to determine the viability of a ship on a long mission than the size of the crew. Even if you can replace 20 normal men with 20 midgets, it may prove more cost-effective to replace them with 10 men and a better set of computers and robots.

Indeed, automation can easily trump this as an effect. But at the same level of automation, you'll get greater efficiency with smaller people.

Again, this only matters if the savings is significant. Remembering the skill issue you pointed out earlier. Which is better:

1) A crew of ten technical geniuses and a heavily automated ship that can do everything except technical genius work, or
2) A crew of ten midgets that take up the same space but are individually less qualified because there aren't enough midgets with aerospace engineering degrees on the planet, equipped with the same automation?

You'd probably have to add twice as many, or even more, midget crewmen to compensate for the lack of qualifications, because you have to train them all yourself and you can't cherrypick genius polymaths the way traditional astronaut corps do. In which case your need for larger crew numbers eats up the savings from their lower individual life support requirements.

All else being equal you save a bit of mass on life support, but all else isn't equal. Plus, again, it's an open question what percentage of the ship is life support in the first place.

Now, I've seen the idea done before- The Space Merchants by Frederik Pohl and Cyril Kornbluth

Thanks! I should probably look that up

Well, that was almost the ideal example of a case where this 'makes sense.' The mission to Venus was a one-shot gimmick for a planet Earth that was physically incapable of launching enough life support to keep a person alive long enough. So they sent one midget.

But again, that was a gimmick. Once the technology existed that doing this was no longer mandatory, it stopped making sense to do so.

[Deebles]

Dawn of spaceflight to near future settings: every ounce that you send up has to be justified, because of the costs and difficulty of getting it out of the Earth's gravity well. Currently the costs are down to $4000 per kilo, so this may not stay relevant for much longer, but still, it's a thing. Also, in an alternate world with an even larger gravity well, and/or a heavier home species, it's possible they could only send up their smaller members in the earlier days of their programme...

Pushing the limits: like the example you gave, if you're straining at the limit of what you can send a certain distance, cutting down on the stuff sent by this amount of mass makes a lot of sense.

Genetic engineering futures: a spacers caste could exist of people genetically engineered to be small, since that could in turn make their ships more efficient.

[Simon_Jester]

In the dawn of spaceflight, the catch is that every ounce you send up has to be justified, but that also means you cannot risk a mission failing because you failed to send up the very best. There are good reasons why astronauts are chosen to be in peak physical as well as mental condition.

I mean, certainly the US, Soviet, or other space programs could send midgets into space if they wanted. Why do you think they didn't? Was it pure irrationality on their part? Or did they maybe consider something you didn't factor in?
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When it comes to pushing at the limits, well, the problem is again that if you don't send the best people, it's an open question why you bothered to send people at all. A slight gain in reducing spacecraft mass, in exchange for being unable to accept qualified crew from 99.9% of the human race, isn't going to pay off.

What long range expeditions need, and have always needed, is a margin for error. They need the most flexible tools and people available because if something goes wrong they have no ability to fall back on outside support. If you can't afford to send a flexible, well-supplied and therefore massive expedition, you probably shouldn't go at all.

[Lord Revan]

I seem to remember that NASA requivers it's pilots to have flown a certain amount of hours as a test pilot or at least a military pilot meaning he or she has to be above a certain height and I can't really see that changing as having a crew that's experienced in dealing with issues that might arise is much more important then a minor weight loss.

[Simon_Jester]

Yes.

Of course, the main reason we use the test pilot/military pilot thing as a qualification is as a proxy for "can this person respond effectively in a crisis involving a complex, technologically sophisticated machine that can move in three dimensions?" For example, the emergency that affected the Gemini 8 mission was one that Neil Armstrong handled fairly well... in large part because of his background as a test pilot.

In general, things like this matter a lot.

[Zixinus]

It would make sense to have dwarf crew if you have a space-born genetically modified population that are dwarfs already. You will need gene-modding to help survive the rigors of outer-space anyway, with genes that reduce bone-density loss and muscle atrophy, plus probably a bunch of other things like radiation-resistance and lack of vertigo from zero-g (though you'll want your population to be under some level of gravity under normal circumstance).

Then it makes sense because the savings add up to the entire space-born civilization with no real downsides.
But when you don't have a genetically-engineered space-born population? Will probably only be significant if the mission is a suicide mission or something.

[Simon_Jester]

On the other hand, physical strength and endurance turn out to be desirable traits under some of the strangest and most unforeseen of circumstances (i.e. extra-vehicular activity). There are tradeoffs.

So it really comes down to a question of "is our spaceborne society so low-margin that we'll genetically engineer our descendants to be midgets specifically so we can build cheaper ships for them?"

I'm unsure that any probable society would sign up for this plan, unless it's one isolated corporation or laboratory's pet project to create cloned space midgets. Usually, people prefer to build up their material infrastructure to fit their children, not impose limits on their children to save on infrastructure.

[biostem]

There'd be other factors to consider, as well; Everything from how deep access panels can go, (due to reduced arm length), to the amount of force that can be required to open or secure a hatch/bolt/nut, (again for similar reason). Also, having a higher ceiling provides more of a "buffer" for things like temperature regulation and extra air in the event of a breakdown in environmental systems. Also, since small people may not have regular body proportions, you may not be able to have shared spacesuits. You'd also have to consider the psychological impact of being in an even more claustrophobic environment.

[Zixinus]

Oh, and in case of developing spaceships aimed at dwarves: if you developed regular-height equipment for your average-to-tall astronauts, it will costs a lot of money if you suddenly have to resize everything. Development of specialized machinery is a big cost in creating spacecrafts, so the clever idea of using dwarf-only crew would have to pay off in long-enough term.

Then there is the question of just using computers or even AI to do the work.

[Deebles]

Yep, I'm increasingly seeing this as not all that desirable. Looking at the real world, even jobs and disciplines with low mass margins generally don't use little people.

The only real-world profession I know of that selects for even smaller-than-normal people due to mechanical considerations is that of a jockey (jockeys generally range in weight from 49 to 54 kg, i.e. 108 to 118 lb). Whereas the overwhelming majority of famous people with dwarfism work in entertainment.

Unless you're in a setting where ship and equipment design becomes relatively cheap, due to automation and simulation, and/or you're designing a ship that's having to push the barest limits of what's mechanically possible, it's unlikely to be a solution that would see much adoption.

Or you invoke aliens. For instance, an alien race living on a world with a significantly larger gravity well than Earth might only be able to send their smallest members up, or even have to gengineer smaller members for space flight.

And in the SG1 verse, a whale-sized species of sentient aliens stumbling on the stargate network might only be able to send their very smallest members through...

[Deebles]

Another real life example of where small size is an advantage would be a Cox in a rowing boat, although there are generally rules to enforce a lower weight limit, e.g. at 50kg for female Coxes and 55kg for Male in international competition, although weights may be used if the weight is under (I'd surmise such rules may be in place to disincentivise an unhealthily low weight, and/or to keep the role open to more people than otherwise, and/or to disincentivise risking a Cox too weak to steer the boat safely for the sake of carrying less weight in the boat).

What's interesting here is that there exists something of a parallel between being the Cox of a boat and the pilot of a small, highly mechanised craft. The smaller you are, the more effective the vessel can be. This creates a role for the very small where pilots take on a gladiatorial role, e.g. in mecha fiction (for all the mechanical issues with mecha). Easy to imagine that a mecha with a smaller pilot could have a better armoured pilot compartment and/or otherwise perform better.

Or to imagine a far post-apocalyptic future where part of humanity survived in shelters (underground or in orbit), and part on the surface. Wherein the former group of survivors would have had to gengineer their children for smaller size to allow them to survive at all as systems failed and resources ran low, while those who survived on the surface might have largely reverted to savagery but also undergone fierce natural selection. So that as the Earth became habitable again, you had smaller folk with high grade weaponry emerge from hiding, possibly inside of giant mecha etc., to meet a world of much larger and stronger but less well-equipped beings. They might not even see each other as human.

[Simon_Jester]

Thing is, coxswains (and their metaphorical cousins in being tiny athletes, the jockeys in horse races) are under a very perverse sort of selection pressure.

They are surplus weight in a sport where the power-to-weight ratio is governed by muscle power, and by a fairly limited total mass of muscle- about 500 kg of rowers, or about 500 kg of horse. So adding a coxswain/jockey increases the total mass of the system to be propelled by 5-10%, and the bigger the coxswain/jockey, the bigger the increase.

BUT the catch is that sport rowing and horse racing are winner-take-all sports in which gaining even a tiny tiny speed advantage can mean the difference between second place and first place. This creates a greater incentive to optimize for pure speed. This is demonstrated by your own speculation: That if it weren't for the weight limits in international rowing competitions, some teams would probably actually have coxswains too lightweight to steer the boat safely.

So basically, the low-mass "pilot" wins out in horse racing and rowing because he's operating a vehicle with an inefficient power source, optimized for the greatest speed possible given the limits of that power source.

When we start talking about giant walking gun platform robots, the incentives change quite a bit. Power sources are more efficient, so you can spare a larger fraction of the vehicle's mass for the pilot and protection. In underground bunkers, it is quite unlikely that dwarfism will make the people in the bunker more survivable because it affects their ability to operate and maintain their own equipment, not just their supply consumption.

And deliberately engineering humans for dwarfism is likely to be difficult, with a considerable risk of screwing up and introducing deformities or disabilities.

So I'm more than a little dubious of this, although the "small folk with technology meet big folk without" imagery is certainly very compelling and creates the potential for interesting stories. Sort of the Eloi/Morlock vibe, but with a twist or three.

[madd0ct0r]

well phenotypically crap nutrition would result in people being much much smaller. If the bunker complex wasn't designed to be such (say, adapted sewers) then you might have corridors and areas that small people can use that bigs can't. I wonder how many generations of walking on your knees it would take?
On the other hand, if you have a sealed bunker/mine, you've effectively got a fixed amount of volume to play with. Even if you dig out a new area, you have rubble you need to distribute somewhere, even crushed and on the floor. Given a few dozen generations, you might have a tunnel system that's twice as long and half the hight.

[Zixinus]

It might be worthwhile, if you are living under circumstances where there is a constant supply but no opportunity to increase that supply for example, to decrease the size of people. You do not need to do dwarfism but to levels of peoples that are referred as "Pygmy". About 1.5m tall rather than the reaching 2-meters high. You can still get small people vs tall people but there isn't real dwarfism** because the ratios of the limbs remain the same**.

Living in a vault where you have a maxed out food supply and you don't want to do something like decrease the number of people, this can be good thing for all.

I wonder how many generations of walking on your knees it would take?

Depends on how much is dependent on going through small spaces to get food. It would be possible for big people to be supported by the smaller people if there is enough food to go around (and especially if there is something that the big people can do in exchange, like fight invaders or something).

**Unless there is more to defining dwarfism. In that case I apologize and please disregard.