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[P]
Self Powered Flight on the Moon?

By carbon in Technology
Sat Mar 02, 2002 at 02:54:16 PM EST
Tags: Science (all tags)
Science

I just read an interesting short story by Heinlein titled "The Menace from Earth", the storyline of which centers around a colony on the moon. The story itself wasn't that exceptional, but it did demonstrate an interesting idea: with a combination of low gravity, high air pressure and special wing equipment, would it be possible to fly on the moon?


Not knowing much of anything about physics or economics or human/bird anatomy or any number of other related fields, I'm not sure if this could ever have a chance of happening. So I'm asking you, the community of kuro5hin, to try and figure out if this would be feasible.

The basic ideas behind how it worked in The Menace from Earth are pretty simple. When the colony in the story had been formed, they found an underground lava-formed bubble several miles in diameter, and used it to contain the (plant recycled) air for the entire city. Eventually, somone figured out that with the high air pressure of the tank (17 psi, which I believe is 2 psi above Earth sea-level), it would be possible to use special flight equipment for fully human-powered flight. The mechanical wings developed for the sport had fingertip controls to regulate airflap pitch, air flow, and sculling, as well as a tail flap for controlling angle of attack. Thrust and lift would come from full-arm flapping, as real birds do. You would only have to run a few yards, and you could rise up into the air up at a fairly steep angle, if you had strong enough arms. From there you could glide around slowly, lift up hundreds of feet, or even do mid-air acrobatics.

This all sounds great, but the theories in it were developed a while ago and with the most emphasis on usability in the story, not realism. As it often seems to do, reality may get in the way. The potential pitfalls I can think of at the moment are:
  • How much air pressure would it really take? And how would you get it there?
  • Even with low gravity, would the human body have any fundamental problems with self powered flight?
  • Is the moon's gravity low enough?
  • Could there really be underground pockets on the moon this big? If not, would it be possible to construct such a thing, perhaps by roofing over a large crater?
  • Would it be a good idea to build a colony on the moon? Or could a business be self-sustaining by making money just selling trips to the moon to fly or walk on the surface ("Fly on the moon for a day! Only $10,000")?
  • What about the cost of getting there, and bringing the construction materials with you?
  • Is low gravity bad for you? How about the gee-forces involved in escaping the atmosphere?
If you want to read the story yourself, I found it in a Heinlein collection called "The Past Through Tomorrow". I have no idea how easily you can get a copy of it today, can any Heinlein fans shed some light on this?

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Poll
How long before we have permanent colonies on the Moon?
o Within 25 years 3%
o Within 25-50 years 21%
o Within 50-100 years 34%
o After 100 years 15%
o Never, physically infeasible to do it safely 2%
o Never, economically infeasible 14%
o Never, space travel is a hoax 4%
o Never, other reason (comment) 4%

Votes: 85
Results | Other Polls

Related Links
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Display: Sort:
Self Powered Flight on the Moon? | 52 comments (44 topical, 8 editorial, 0 hidden)
moon flight (3.50 / 6) (#1)
by zephc on Fri Mar 01, 2002 at 03:06:46 AM EST

a 'bubble' on the book probably doesn exist, at least not in a nice shape condusive to flight. However, if you created a a larged domed colony area on the moon, with enough room to fly around, and you pressurized it with earth-level pressure (so we could breath) you would need considerably less force to keep a winged transport aloft. Flapping-wing transports (often called ornithopters) are fun to think about but are terribly inefficient with modern tech.

ornithopters (4.00 / 1) (#6)
by ragnarok on Fri Mar 01, 2002 at 07:02:14 AM EST

Terribly inefficient beasts. Our muscular structure isn't up to the level of power under Earth Gravity, to build up enough lift to counteract the weight and drag of the human body. Drop the weight, while keeping the air pressure the same, and you might have a flying chance. But then you've got the drag, and the human body's not designed as anything, only adapted to the current rock-ape role.

Basically our muscles are too weak, and our bones are too solid.


"And it came to healed until all the gift and pow, I, the Lord, to divide; wherefore behold, all yea, I was left alone....", Joseph Smith's evil twin sister's prophecies
[ Parent ]

Ornithopters? (none / 0) (#25)
by baberg on Fri Mar 01, 2002 at 01:38:54 PM EST

Come on, that was a great card! A 0/2 flying artifact creature for 0 mana? It buys you one more turn against a Shivan Dragon, or can even be used with a Howl from Beyond to deal some real damage to an unsuspecting player! Ornithopters are even useful for sacrificing to your Atog, to give him +1/+2 for the turn.

Ornithopters useles... bah!

[ Parent ]

Some data: (4.42 / 7) (#2)
by xriso on Fri Mar 01, 2002 at 03:17:12 AM EST

Earth atmospheric pressure: 1 atm = 1.013 x 10^5 Pa = 14.7 psi
Earth gravity: 9.80 m/s^2
Moon gravity: 1.62 m/s^2 = 16.5% (about 1/6th) earth gravity

So, I would say that for an Earth plane to fly on the moon, assuming that lift is proportional to pressure, you would only need 1/6th the speed or 1/6th the pressure or some combination for that plane to fly. As for humans, I don't know how much lift we could create.

Fundamental problems with self-powered flight? It would be necessary to do what hangglider pilots do: a full-body support structure, and you would definitely want some sort of default wing position of being horizontal instead of pressed up against each other behind the back (don't pull the arms all the way back).

A pocket like that is unlikely I'd say. It requires gas to be trapped under the moon's surface form the bubble, which would make me wonder: how did that gas get there?

The rigors of getting form earth to moon shouldn't be too bad, but the low gravity could be harmful with time. You would want to regularly excercise to keep your muscles nice and strong. In the Mars series of books by somebody or other, the people born on Mars grew up with lower bone density. They were well suited to Mars, but if they wanted to go to Earth they would have a hard time. I have no idea whether this would actually happen.

Also, I think the moon is a pointless venture. The only place where it could be worthwhile would be Mars (maybe).
--
*** Quits: xriso:#kuro5hin (Forever)

Responses (4.66 / 3) (#4)
by carbon on Fri Mar 01, 2002 at 03:44:54 AM EST

So, I would say that for an Earth plane to fly on the moon, assuming that lift is proportional to pressure, you would only need 1/6th the speed or 1/6th the pressure or some combination for that plane to fly. As for humans, I don't know how much lift we could create.

But this is why the pressure is higher then earth normal and the gravity lower, because the goal is to make it as easy to fly as possible.

Fundamental problems with self-powered flight? It would be necessary to do what hangglider pilots do: a full-body support structure, and you would definitely want some sort of default wing position of being horizontal instead of pressed up against each other behind the back (don't pull the arms all the way back).

I can understand the need to keep the wings horizontal by default, so that gliding would be easy, but why would you need a support structure? It seems that with a big enough surface span, you would only need the tail and wing assemblies, and could glide easily enough by just keeping these level.

A pocket like that is unlikely I'd say. It requires gas to be trapped under the moon's surface form the bubble, which would make me wonder: how did that gas get there?

Lava? Heh, add "geology" to that list of sciences I know very little about :-)

Also, I think the moon is a pointless venture. The only place where it could be worthwhile would be Mars (maybe)

Well, I can understand this view for a general purpose colony, but for just the flight thing, wouldn't the moon be better? (less gravity, closer).



Wasn't Dr. Claus the bad guy on Inspector Gadget? - dirvish
[ Parent ]
more important question: (4.46 / 15) (#3)
by dr k on Fri Mar 01, 2002 at 03:37:08 AM EST

If a werewolf were living on the moon, would he change into wolf form when the moon was full from Earth, or when the Earth was full? Or would he be a wolf all the time?

[OT] Probably in 14 day shifts (none / 0) (#23)
by ocelotbob on Fri Mar 01, 2002 at 01:24:25 PM EST

Were our lycanthropic astronaut to live on the lunar surface, I'd imagine that e would be rampaging for 14 day shifts, corresponding with the period eir colony is in the sun, or away from the sun. I can't decide which one better fits with the lore, though I'm leaning towards the period of darkness; the whole lore of werewolfs centered around when hunting is easy for the local wildlife. But the real question is, what would the carnage cycle be if said shapeshifter sailed aboard a starship?

Why... in my day, the idea wasn't to have a comfortable sub[missive]...
--soylentdas
[ Parent ]

Oh (3.80 / 5) (#5)
by qpt on Fri Mar 01, 2002 at 06:26:31 AM EST

For a second, I thought you were going to write about self-powered flights to the moon. That would have been altogether more interesting.

Domine Deus, creator coeli et terrae respice humilitatem nostram.

I can't believe (3.00 / 3) (#7)
by greyrat on Fri Mar 01, 2002 at 08:38:51 AM EST

no one has made the obligatory Honeymooner's reference. Jackie Gleason would be very dissapointed...
~ ~ ~
Did I actually read the article? No. No I didn't.
"Watch out for me nobbystyles, Gromit!"

Possible (3.00 / 2) (#8)
by ChiefHoser on Fri Mar 01, 2002 at 08:56:43 AM EST

It is theoretically possible for humans to fly self propelled (using wings that is), whether it be on the moon or on earth. The problem being that we are not built to do it here on this pale blue dot so we'd end up having to flap our arms (with wings attached somehow) in a similar fashion to a hummingbird. On the moon however it would be slightly more efficient for a human to fly. Incredible upper body strength would still be required but gliding is always an option, and if you bring in thermo-currents (ie. like those used by eagles and the like) then it might even be easier. I would not be suprised if something like this occurs as recreation on the moon, assuming we ever get there that is.

If you like Heilein you should read "The Moon is a Harsh Mistress", it is one of my favorites, but the whole future history (past through tommorrow) stuff is good (The Man Who Sold the Moon is my favorite out of that collection).
-------------

Chief of the Hosers
Practicality and Why? (2.50 / 2) (#9)
by Woundweavr on Fri Mar 01, 2002 at 09:02:16 AM EST

This doesn't have a whole lot of practicality. If the moon was bubbleless, control would be a problem. It'd be more or less space so there's both less to push off and less to slow you down with drag. As far as personal flight.... why? First of all you'd have to have some way to control yourself. It's not like you can "swim" in the space, it wouldn't make any difference. High pressured air would be useless except on liftoff. Rocket pack type things run into the same problems as on earth. It just wouldn't be practical.

In a bubble, why bother? The only advantage in a bubble would be less gravity than on earth and so flight still would probably not work.

Birds flying don't just stay up by flapping (and wing shape obviously). They actually push on the air around them. I don't know if the moon has enough atmosphere to support this type of thing, even with a fraction of the gravity.

Atmosphere? (4.00 / 1) (#12)
by schrotie on Fri Mar 01, 2002 at 10:05:46 AM EST

I don't know if the moon has enough atmosphere to support this type of thing, even with a fraction of the gravity.
Moon has no atmosphere. That's probably not enough ;-)

[ Parent ]
Well technically it has some but same result -nt- (none / 0) (#19)
by Woundweavr on Fri Mar 01, 2002 at 12:03:16 PM EST



[ Parent ]
Human powered flight works on Earth (4.50 / 4) (#11)
by georgeha on Fri Mar 01, 2002 at 10:02:58 AM EST

MacReady proved it back in the 1977 with the Gossamer Condor. Given that the main issue is getting enough vertical lift to offset gravity, in 1/6th the gravity you would need 1/6th the energy, so almost anyone who could ride a bike could fly a Gossamer Condor type craft in a large bubble on the moon at standard atmosphere.

So, could a human fly like a bird, with flapping wings? I'm not sure, the bone geometry is a little different, and pecs aren't nearly as strong as leg muscles.

Flying on the Moon? (2.75 / 4) (#13)
by jabber on Fri Mar 01, 2002 at 10:29:18 AM EST

Not knowing much of anything about physics or economics or human/bird anatomy or any number of other related fields, I'm not sure if this could ever have a chance of happening.

You're very wise to disclaim your complete ignorance on the subject. The sort of flight you're babbling about requires an atmosphere, which the Moon lacks. So, unless we're doing our aerobatics in the 'Lava Bubble' (Bahahahaa!), this idea isn't going to fly.. [bad pun, go sit in the corner]

Further, assuming we are in this 'bubble' (it isn't clear in your write-up that we are) it would all depend on how deep under the surface it is.. The closer to the center of a mass you get, the less the mass affects you gravitationally.. For example, if you were in the center of the Earth, you would be weigthless. Of course, due to the motlen metal, you'd also be dead.

They're G-forces (as in 'Gravitational' ones), and we do not escape the 'atmosphere'.. We climb out of the 'gravity well'..

This article is so full of naive holes that it makes the whimsical idea of man-powered flight completely trite and unworthy of discussion. Sorry.

[TINK5C] |"Is K5 my kapusta intellectual teddy bear?"| "Yes"

Huh? (none / 0) (#21)
by dennis on Fri Mar 01, 2002 at 01:15:55 PM EST

You're very wise to disclaim your complete ignorance on the subject. The sort of flight you're babbling about requires an atmosphere, which the Moon lacks.

Perhaps you didn't read this part of the writeup:

they found an underground lava-formed bubble several miles in diameter, and used it to contain the (plant recycled) air for the entire city. Eventually, somone figured out that with the high air pressure of the tank (17 psi, which I believe is 2 psi above Earth sea-level), it would be possible to use special flight equipment for fully human-powered flight.

Seems pretty clear to me. The bubble would have to be awfully deep for the gravitational effect you describe to be significant at all.

[ Parent ]

Actually, as I read it.. (none / 0) (#33)
by jabber on Fri Mar 01, 2002 at 03:46:20 PM EST

It could also mean that the air pressure in the bubble could be used as a propellant of sorts.. Much like the air pressure in a Super Soaker allows water to fly. The words "Fly inside the 'cavern'" would have removed all ambiguity.

[TINK5C] |"Is K5 my kapusta intellectual teddy bear?"| "Yes"
[ Parent ]

Got me (none / 0) (#29)
by carbon on Fri Mar 01, 2002 at 02:49:18 PM EST

Further, assuming we are in this 'bubble' (it isn't clear in your write-up that we are)

Er, sorry. Well, just to make it clear, I know that decent air pressure would be required for things like, say, turning :-)

They're G-forces (as in 'Gravitational' ones), and we do not escape the 'atmosphere'.. We climb out of the 'gravity well'..

Yeah, got me here, oops

This article is so full of naive holes that it makes the whimsical idea of man-powered flight completely trite and unworthy of discussion. Sorry.

Any others you noticed that I'm messing up on? I'm always happy to be better informed on interesting stuff like this.



Wasn't Dr. Claus the bad guy on Inspector Gadget? - dirvish
[ Parent ]
Fair enough (none / 0) (#34)
by jabber on Fri Mar 01, 2002 at 03:58:34 PM EST

Not just turning.. Gliding. Do a quick Google search on the aerodynamics of how aircraft wings work.. It's not so much 'pressure' as it is 'density' that makes 'lift' possible.

When you're next at a bookstore, browse a CliffNotes or For Dummies version of a High School Physics book. The idea of how stationary wings work is a traditional example. After that, I would suggest looking at how wing shape and joint articulation allow a bird to take off and land without the aid of an engine to provide thrust.

Once those ideas start to make sense (you don't have to do any messy math to get a feel for it) you might want to learn a bit about gravity, and how it varies when you climb a mountain or go into a mine.. The reasons behind gravity being less of a factor underground involve integral Calculus, and mine is rusty..

Suffice it to say that when going underground, you can pretty much ignore the gravitational effect of the layer of matter surrounding the planet above your given location.. It's like peeling an onion really.. By being able to ignore all that dirt, the relevant mass of the planet, which is where it's gravity comes from, is decreased, and so your weight decreases accordingly, making flight easier - especially given an adequately dense medium to fly in.

[TINK5C] |"Is K5 my kapusta intellectual teddy bear?"| "Yes"
[ Parent ]

3001 and low gravity (5.00 / 1) (#14)
by hardburn on Fri Mar 01, 2002 at 10:47:22 AM EST

In 3001, there is a point in the story where you have people flying in low gravity using devices roughly like bird wings.

Low gravity can be quite harmful. It causes your bones to shrink and your muscles to weaken. Essentialy, your bones and muscles are only as strong as they need to be in order to do whatever it is you're doing. Since there is less work to be done in low gravity, these parts of your body weaken.

Astronauts do a lot of exercise to help stop these effects. These exercises usually involve pushing one set of muscles against the other. I suppose the flying thing might help stop the effects of low gravity, but you'd actualy have to go try it and do some medical studies to find out for sure.


----
while($story = K5::Story->new()) { $story->vote(-1) if($story->section() == $POLITICS); }


Re: 3001 and low gravity (none / 0) (#38)
by Rk on Fri Mar 01, 2002 at 06:16:28 PM EST

Low gravity causes muscular dystrophy - which is bad enough that astronauts/cosmonauts returning from the ISS are often unable to stand with assistance after the shuttle touches down. Low gravity causes a lot of other anatomical problems too, which is why most serious proposals for space colonisation involve some means of artificial gravity, usually involving centripetal force. (spinning space stations, I'm sure you've heard of the concept...)

This article goes into the medical effects in more detail.

[ Parent ]

Atrophy (none / 0) (#41)
by Happy Monkey on Fri Mar 01, 2002 at 09:19:29 PM EST

Low gravity causes muscular dystrophy

I think you mean "atrophy". Muscular Dystrophy is the disease that Stephen Hawking has.
___
Length 17, Width 3
[ Parent ]
WRONG! (none / 0) (#44)
by Mr. Piccolo on Fri Mar 01, 2002 at 11:45:00 PM EST

Stephen Hawking has ALS, better known as "Lou Gerhig's Disease". Of that I am certain. Muscular dystrophy somehow involves Jerry Lewis's Kids, but it's definitely not the same thing.

The BBC would like to apologise for the following comment.


[ Parent ]
Doh. (none / 0) (#50)
by Happy Monkey on Sat Mar 02, 2002 at 08:49:50 AM EST

But low gravity gives you neither.
___
Length 17, Width 3
[ Parent ]
Is it a Bird? Is it a plane? No, it's Supergroby! (4.33 / 3) (#15)
by schrotie on Fri Mar 01, 2002 at 10:47:54 AM EST

As has been pointed out, bird flight is not just flapping wings. They do a lot of control stuff including adjustment of single feathers or small groups thereof.

Ever ate a chicken? Note the prominent fin shaped bone down at the chest? The prurpose of that relatively huge bone is to yield a fix point for the yet huger flight muscels (the whole white breast flesh). And chickens are miserable flyers.
The inside of a bird's chest is mostly lungs to fuel all that muscels with oxigen. And we are talking bird lungs here, not the primitive sacks we house in our chests. Bird lungs are eleborate counter flow exchangers that are orders of magnitude more efficient than our lungs.

To do anything that remotely looks like birdflight (assuming moon gravity) one would have to move something like 10-15 kilogramms (no stunts, for airstunts you can multiply that with 2-4 depending on your speed) perpetually up and down ... with strechted arms. Maybe if you are extremely well trained, you can sustain yourself for a couple of minutes that way. But you probably could not control your wings sufficiently flapping with all your might. Thus coloibri style flight is pretty much out of the question. Bigger birds mostly use thermal forces like hanggliders do. They can use flapping to get speed but not much for the lift. Most wing movements of bigger birds are controle movements (their way of "turning the wheel").
Humans are built to walk or run. Almost any animal outperforms us even there, but anyway, that's where we are best. Thus a human powered ornithopter would probably have to use the legs for producing most of the power and the arms and hands mostly for control. Learning to fly would still probably take a long time (if it's possible at all). But given moon gravity maybe humans could do that. I'd rather stick to hanggliders though.

By the way, I don't think air pressure is all that important. What keeps birds (and planes and helicopters) up is not their flapping (or wing angle) against the "thickness" of the air, but the pressure difference between the air stream above and below the wing. I don't know much airodynamics but I assume one can design wing profiles according to air pressure. That helicopters have hight limits is a problem of helicopter design: close to the rotor axis, the rotors move very slowly through the air, at the tips they move very fast. And helicopter rotors have a relatively "primitive" wing profile, that's far from optimal for ensuring air flow adhesion. The reason for that is the pecular way in which helicopters controle their flight. Planes can fly through very thin air. They fly faster then, but effectively use less energy per distance covered.

Air pressure is very important (4.00 / 1) (#17)
by georgeha on Fri Mar 01, 2002 at 11:08:59 AM EST

as the lift force caused by the pressure differential is directly related to air density. Halve the pressure, and your lift force is halved.

[ Parent ]
Unconvincing... (none / 0) (#22)
by Parity on Fri Mar 01, 2002 at 01:22:28 PM EST

I find your thought-exercise unconvincing as an argument; by similar logic, one would believe that humans couldn't swim... and while I doubt human wings would be precisely bird-like, I think there's a lot of range between hummingbird 'treading-air' and hawk thermal gliding, and that artificial wings would be a compromise. Anyway, despite my own thought-exercises here, my point is that without numbers or science, I'm unconvinced by your thought exercise, and while I believe my thought-exercises more, they aren't convincing either. :)

Parity Odd



[ Parent ]
Unconswimming (none / 0) (#39)
by schrotie on Fri Mar 01, 2002 at 07:18:56 PM EST

by similar logic, one would believe that humans couldn't swim
I'd be interested to see you exercising similar logic for that hypothesis. Actually humans sport a couple of adaptions for swimming. We are the only primates of the closer family (read apes) with skin (web?) between their fingers and toes. We have not much body hair. We can hold our breath as long as orcas (don't know how other apes fair in this discipline). Most obvious: our nose has its holes downward so that no water can get in. Our body is long and smooth, outright streamlined (mark our ears, the rest should rather be regarded as an adaption to upright gait).
There is a theory that all this is no coincident, but that theory is not very popular as far as I know. One (controversial but rather popular) theory however postulates that humans populated the planet by migrating along the coasts of the oceans. There is also evidence for this. Maybe these are really adaptions to hunting/gathering food in/under water. Anyway, we are very well equipped for swimming.

As for flying: our arms are rather long (levers) and the breast and back muscels rather weak. Lie down on your back with your arms stretched orthogonal to your body. Try lifting ten kilos that way (with completely stretched arms). Got it? Great! Now lift it, hold it 10 seconds, put it down, lift it, hold it ten seconds, put it down. Enjoy flying?
I did not say the Heinlein scenario is impossible, I said it'd be pretty exhausting (assuming big bird like flight, humming bird is not possible I think). And I said that using the legs for power production and the arms for controlling the wings would be a much more convenient approach.

[ Parent ]

Hey (5.00 / 1) (#16)
by notafurry on Fri Mar 01, 2002 at 10:55:03 AM EST

Whadda ya mean, the theory's not workable?

For the record, Heinlein had a degree in mathematics. He was one of the first "hard" science fiction writers; if he said foo was true, and provided numbers, then it is highly likely that foo is indeed true to the limits of science as known at the time.

The mathematics of human-powered flight do work out on the Moon, and actually on Mars as well, given a high enough pressure. The 17 psi mentioned is not a baseline figure; sea-level pressure would be adequate, on the Moon.

The only part of the theory that would currently be considered untrue or unlikely is the presense of open "lava bubbles". They do exist on Earth, but none have been detected on the Moon. That doesn't mean they can't exist - but it does make it less likely.

People looking for the story will also find it in a short collection (8 stories) entitled "The Menace from Earth" and bearing a stylized image of a woman with wings on the cover. My copy is copyright 1959, with a separate copyright for the story "The Menace from Earth" listed as 1957 for "Fantasy House, Inc." The same collection includes one of the most famous Heinlein short stories, "Columbus Was a Dope".

mars conditions based flight sim (4.75 / 4) (#18)
by swifty on Fri Mar 01, 2002 at 11:51:26 AM EST

there's been a multi-platform flight sim out for a while called X-Plane that relies on blade element theory for its flight dynamics. recently the author programmed the atmospheric and gravitational conditions for mars into the sim. an excellent description of the results can be found here.

Freiheit ist immer auch die freiheit des anderen.
From my PHY156 notes... (none / 0) (#24)
by Spatula on Fri Mar 01, 2002 at 01:26:07 PM EST

Vescape=SQRT(((2(M)(G))/(R)))

M=mass
G=gravity
R=radius

Still, I have to call my prof, as I'm not sure of the definitions. Hope this helps.
--
someday I'll find something to put here.

Thought this too but... (none / 0) (#43)
by Woundweavr on Fri Mar 01, 2002 at 10:13:16 PM EST

Its pretty irrelevent. The escape velocity on the moon is 2.38 km/s, which is like 1/5 of that of earth. No one is getting up to that speed by the strength of their muscles or simple machines.

[ Parent ]
Still... (none / 0) (#48)
by Spatula on Sat Mar 02, 2002 at 03:17:39 AM EST

...it is a formula to keep in mind. I am assuming, of course, that the said expedition to the moon would result in future expeditions to other moons/planets. After all, as Largo has said, "Knowledge Is Power" ;)
--
someday I'll find something to put here.
[ Parent ]
repost on april 1 (1.00 / 1) (#27)
by bsmfh on Fri Mar 01, 2002 at 02:11:05 PM EST

no flight without atmosphere.

jet-propelled rocketeering is OK and do-able

you got a lot of people going on this, but it's still just (the lack of) hot air....

--b

Not quite (none / 0) (#28)
by carbon on Fri Mar 01, 2002 at 02:17:05 PM EST

A lot of people have commented this, and I'll just respond here. Yes, I understand that you require air pressure in order to have something to fly on, otherwise you would only have Newton's third law to use to change your velocity. Notice that I specifically mention that you would require some sort of contained air space. Ha! :-)



Wasn't Dr. Claus the bad guy on Inspector Gadget? - dirvish
[ Parent ]
Let's play with some numbers (none / 0) (#30)
by sigwinch on Fri Mar 01, 2002 at 03:22:23 PM EST

Gliders on Earth do 40 knots (20 m/s) with a 10:1 glide ratio. Assume we can go ~1/6 as fast for the same glide ratio, that's a speed of 4 m/s, which means you fall 0.4 m every second.

How much muscle power does it take to lift yourself at 0.4 m/s? That's equivalent to (0.4 m/s)/6 = 0.07 m/s on Earth, or 7 cm/s. About the same as climbing stairs at a rate of one step every three seconds.

For a body + flyer weight of 100 kg, that's 60 watts of mechanical power, which is not much. For reference, just doing office work at a desk burns 100 watts.

I'm making lots of assumptions, but IMHO human-powered flight is energetically feasible on Luna. (Yeah, yeah, assuming atmosphere...) Even if just upper-body strength is used, it seems doable if you're in good shape.

I think the concerns about flight posture are overstated. You can always use wires, pulleys, and levers to adapt human motion to wing motion.

--
I don't want the world, I just want your half.

Until the US releases it's iron grip. (4.00 / 1) (#31)
by OS24Ever on Fri Mar 01, 2002 at 03:39:53 PM EST

First off, I am a US citizen. I've been very disappointed with the US Space program since the close of Skylab. We went to the moon over 30 years ago now and have done not much exciting stuff since then. Sure we take a little craft up into orbit, and come back down. Great. Where is the first man on mars? Why haven't we gone back to the moon? Come on people.

Until the US releases it's iron grip on space travel the moon will never be colonized. It's bad enough that every time another country besides the US starts to offer less expensive methods of getting sattelites into orbit NASA condems their methods in favor over thier cost overrun secretly funding DOD project prices.

I highly suggest reading 'Back to the Moon' by Homer Hickam (Of October Sky fame) who discusses NASA's politics and the feasability of less expensive space flight. It is a great story ,but also quite the commentary on the death grip the Oil Industry seems to have on non-oil related products.




NASA is (none / 0) (#40)
by medham on Fri Mar 01, 2002 at 08:57:59 PM EST

And always has been a PR campaign for the militarization of space. The moon voyages, to take the most egregious example, were of no scientific value.

The real 'medham' has userid 6831.
[ Parent ]

The moon missions' (none / 0) (#46)
by fhotg on Sat Mar 02, 2002 at 02:27:27 AM EST

scientific value is embodied in the rock samples brought back. While this increased our knowledge quite a bit, a manned mission wouldn't have been necessary for this and giganticly inflated the economical costs. There was no military use to gain from these missions either.

The real reason for the Apollo program laid in the necessity to reassure the superiority of the ideology, after Yuri scared the hell out of them.

[ Parent ]

scientific value (none / 0) (#51)
by mikeliu on Sat Mar 02, 2002 at 11:20:05 AM EST

I would suggest that the scientific value came from the concerted effort of developing the lunar program, and then proving it was valid by actually doing it.

What wasn't so important was what got done while we were there. What was important was showing that with the technologies that we had, we could get it done, while hopefully we picked up a thing or two in the course of it all.

[ Parent ]
not everyone yet (none / 0) (#47)
by adiffer on Sat Mar 02, 2002 at 03:10:07 AM EST

We haven't all been knocked down by the big bad government yet. There is a trick to it. Don't threaten their livelyhoods unless you actually have the power to win.

Follow the domain behind my email address if you are curious. 8)
-Dream Big. --Grow Up.
[ Parent ]

Some Day (none / 0) (#45)
by Ashcrow on Sat Mar 02, 2002 at 01:35:02 AM EST

It won't happen untill the US stops terrorizing outer space. We act like it belongs to us and our allies. I think once we back down and allow anyone into space without going by our red taped books there will be a colony planted by another country (or at least lots of research in the direction of).


----------
"Are you slow? The alleged lie that you might have heard me saying, allegedly moments ago? That's a parasite that lives in my neck."
Fly like a bird? Nah. Fly like a dolphin! (none / 0) (#49)
by IvyMike on Sat Mar 02, 2002 at 03:28:33 AM EST

There's a sci-fi short story about this, and of course I've forgotten the title, the author, and most of the details. But the jist of it was: humans in a low gravity environment were trying to learn to fly with bird-like wings. It wasn't working; people could get airborne, but they had almost no control. The solution? Don't think of it as flying through the air, think of it as swimming!

Just doing some visualization, I think that flippers, "webbed" suits, etc. seem like something I could adopt to wearing and using a lot easier than a pair of wings on my arms.

If you remember anything about the story, please follow up with the details.



Social issues (none / 0) (#52)
by bob6 on Sat Mar 02, 2002 at 12:02:33 PM EST

I read that short story and I recommend it even if you are not a sci-fi lover. I liked it because Heinlein takes into consideration a lot of consequences of moon flying including 'social' aspects :
  1. People, especially young people, go flying like people go to beach in earth coastal cities. They use it for relax and gossip.
  2. A fly code developped by itself similar to drive code because many people fly in the same place. There is a wing color (orange) for beginner flyers, complex priority rules, for instance ascending flyers have priority over descending flyiers.
  3. There is several qualities of wings ranging from second hand standard obsolete glide-only wings to the super hi-fi carbon fiber customized wings. Exepert fliers call themselves 'birds' and use obviously high quality wings which are controlled through complex movements of wrists, head and even tongues.
I think these interesting isues will appear when (if) we will able to fly.
However there is one thing I don't agree with Robert Heinlein : he assumes that low gravity would make poeple have a light bone frame. I think it's quite the contrary because lower gravitational force allows for bigger bones without additionnal energy expense.

Cheers.
Self Powered Flight on the Moon? | 52 comments (44 topical, 8 editorial, 0 hidden)
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