APOD: Wanderers (2014 Dec 08)

[Ron-Astro Pharmacist]

Some might deem this impossible until you look back upon what humans have already accomplished. Then all or more seem inevitable given those who dream. We may never be able to live in the future but we all can imagine. The only limitations will be placidity. But oddly that is the feeling this film evokes in me. It has a calming effect that comes from knowing it will be someday. Showing it's not enough to conquer the planets, future beings must venture to the stars to relieve the restlessness portrayed by flying amongst Titan's noxious clouds or diving off of Miranda's cliffs. For the filmmaker to create that emotion from something that has not yet happened is quite like sorcery.

What will the star wanderers do to relieve their edginess and where will they fulfill their dreams? Maybe they already have?

[thermium]

At 2:25, people are shown walking in the magnetospere of Jupiter, presumably on the ice sheets of Europa. This would be very cool if the radiation environment there were survivable by humans, but it isn't. Without extensive shielding, a 10 minute walk would be deadly.

[Chris Peterson]

At 2:25, people are shown walking in the magnetospere of Jupiter, presumably on the ice sheets of Europa. This would be very cool if the radiation environment there were survivable by humans, but it isn't. Without extensive shielding, a 10 minute walk would be deadly.

Well, given that nothing like this is going to happen for 1000 years or more, who's to say what protections advanced shielding materials or advanced medicine or genetic engineering will offer?

[munnecke]

Awesome video, but the the link to the "no one knows the future" showing the home computer vision of 1954 is a hoax. http://www.snopes.com/inboxer/hoaxes/computer.asp

[DaveGeology]

Baseball sounds like Vin Scully. Man's destiny sounds like Carl Sagan.

[JohnD]

Chris,
"I don't see a problem here. This form of recreation has been discussed in many places. Given the very low surface gravity of small bodies, it is completely possible to jump from cliffs if they are not too high (a kilometer, perhaps) and still arrive at the bottom with a low enough velocity to land on just your legs. And of course, we don't know what other arresting devices might be provided."

Really? Please check my maths:

On Miranda
Time 't' taken to fall distance 'd' under gravity is SQR(2d/g) = SQR(2 x 1000m/0.08) = 158seconds
Velocity after that fall is gt = 0.08 x 158 = 45.5m/s (= 28.27mph)

Doesn't sound to bad, does it?

So compare with an Earth fall.
Velocity 45.5m/s after 9.8 x t seconds
So t = 4.64 seconds

How far would you you freefall on earth in that long, from a standing start?
d = 1/2 x gt^2 = 1/2 x 9.8 x 4.64^2 meters = 106 meters, or just under 350 feet.

After falling a kilometer on Miranda, you would be falling as fast as you would after falling 106 meters (350ft) on Earth.
Your weight on Miranda might be a fraction of your Earth weight, but your mass will be the same.
You make that jump, Chris, not me.
Not without a jet pack, anyway, because a parachute would be as useless as a chocolate teapot.

Cheerio, Guv!
John

[Chris Peterson]

Really? Please check my maths:

On Miranda...

Yes, but Miranda was not my example. Miranda is a few hundred kilometers across. How about trying this on a small asteroid or comet?

[alex_space]

At 01:53, theu put a ying-yang symbol in crater; Why ?

[Chris Peterson]

At 01:53, theu put a ying-yang symbol in crater; Why ?

I'm thinking it might be a goldsworthy.

[tarazed]

@Cousin Ricky
Good to know it does work. I am on Mageia4 and the Flash plugin in their repositories may not be the latest. I have the Fluendo h264 codec but don't know if that is compatible with a browser.

[questioneer]

The critical question is this: where would human being obtain the raw material to build the heavy weight space machinery to journey where no man has gone before?
Carrying out space exploration demands raw material on a grand scale. With environmental factors imposing legitimate restrictions on the use of the Earth's natural resources for planetary exploration it would be wise to first address the source of raw materials to be used in building star ships. Engineers must design technology to transport human being en masse to distant worlds and search for a non-terrestrial source of raw material to build the star ships.
Rocket propulsion cannot meet the demands of such large scale interstellar and interplanetary endeavors. Rocket technology was used to land man on the Moon and carry out preliminary exploration of the Solar System. It enabled installation of the Hubble Space Telescope into Earth orbit so that human being can truly see and understand the startling fabric of the universe. The search for habitable worlds similar to the Earth will require technology and sources of energy and materials that human being are not familiar with at this time. Perhaps the assistance of extraterrestrial aliens can catalyze the effort - but the endeavor must be a unique human experience. In this regard man is alone. Its every civilization to himself. There will planets which will be hospitable to human being - but if such planets are already inhabited by intelligent creatures then it would be best to avoid them, and to continue searching for hospitable planets that are not inhabited.
The non-terrestrial source of raw for such an endeavor are asteroids. An asteroid will function as both the source of raw materials and the living space for such an interplanetary mining operation. As raw material is excavated out of an asteroid a cavity will be produced which may be conditioned to function as living space for man and beast. Consider an asteroid approximately 100 km in diameter - an excavated cavity of 10 km3 may function as living space for people and pets and botanical gardens.
Asteroid 41 Daphne would probably be a suitable body to set up a an initial mining operation. Diameter is approximately 171 km and mass in the order of 7.03 quadrillion tons. Density of asteroid Daphne is thought to range between 2.0 gram/cm3 and 2.4 gram/cm3 which means that the asteroid is essentially composed of rock. A 1 km3 volume of the asteroid would yield enough iron to meet human needs for the next hundred years.
The future is this moment.
This is a good time to review the soundtrack of the original documentary Cosmos - preferably in vinyl LP record. It is a good time to think through the technology of the vacuum tube and the amplifiers designed to reproduce music.
There are planets out there similar to the Earth, as anyone who has watched the movie Contact would know. Some have more than one moon, some have more than one sun. There are frozen Earth-like planets that are accompanied by rings and an atmosphere-bearing moon.

But, how would you find them?

[LocalColor]

Hearing Mr. Sagan's voice gave me goosebumps. Inspiring video!

(I was hoping this was a trailer for a full movie, sigh.)

[Wadsworth]

Excellent video. Surely some of the ideas were derived from the Mars trilogy books.

[O. Ehontas]

That video used Carl Sagan's voice, but would he have approved of it's physics content?

1/ Jumping off a high cliff on a low gravity body. Yes, you float down as shown. But gravity is gravity and mass is mass. If your fall was as far as shown, you would still be travelling quite fast at the bottom, with no means of slowing down. Death, from impact or vacuum, unless of course, you had a jet pack.

2/ Those blimps, apparently on Mars. Bigger crew/cargo quarters than an Earthbound dirigible, but the envelopes are the same/smaller, in an atmosphere with a density equivalent to the Earth's, 35 kilometers high. They just wouldn't take off, even if 'filled' with vacuum.

3/ And what was that 'star ship on a rail'? At first I though it was on a space elevator built from the Moon - good idea! Less garvity to start with, but it morphed into something in deep space.

JOhn

Time hacks on your list would have been nice, but let's make some assumptions.

1/. If you look really closely between 1:47 and 1:48 (I know, not a whole lot of time there), the cliff "diver" is not actually cliff diving. S/He is actually bungee jumping. When the person leaves the cliff, they are trailing something as they leap. When the view shift to the looking up mode, the cord is to thin to be visible.

2/. On this one, I don't have a real good response to. The amount of viewing time and perspective don't give me enough info. However, on a side note, numerous agencies have been playing with dirigible airframes in the last 15 to 25 years or more as an alternative to standard aircraft. I have heard rumors of plans for dirigibles up to and over a mile in length. With materials sciences advancing almost as fast as electronic developments and with some of the fiber and ceramics coming on line, who's to say what would be possible in 1000 years. Or less.

3/. The "star ship on a rail" is almost exactly what you thought it was at first. Right idea, wrong body. If you follow the tracks from 1:34 to 1:38, you will see that it is descending into a fairly large 'port on the night side of the planetary body (I'm assuming Mars by the coloration, but I could be wrong). The deep space illusion is due to the size of the 'port it is descending to.

And finally in summation, yes, Carl Sagan was an astrophysicist (among many other -'ists), but he was still a dreamer. I don't mean a dreamer in the negative sense, but rather as one who hoped for more and better from the human race. I found the use of his words and voice for this video highly appropriate and suspect that he would have as well. This video was about mankind's dream to go elsewhere, or as Mr. Sagan so aptly put it "The open road still softly calls, like a nearly forgotten song of childhood." Space and the stars are that open road.

[JohnD]

Really? Please check my maths:
On Miranda...

Yes, but Miranda was not my example. Miranda is a few hundred kilometers across. How about trying this on a small asteroid or comet?

Yes, you did not identify the site of the BASE jumping as Miranda, someone else did, but you did say "kilometer high cliff" and in the background to that scene is a planet that could easily be Uranus. Philae showed how to jump a kilometer high and land safely on a comet only a few kilometers across, taking two hours to get back down again, but that was not what was shown in the video.

o.Ehontas,
to take your points in order:
1/ Look again. No bungee, just some rock fragments flying off as the thrill seeker jumped out to his death.

2/Yes, it is difficult to get the scale of those dirigibles, they could be miles long. But then their payloads would be nearly a mile long too. The ratio between balloon and payload size depends strictly on the ratio between the densities of the atmosphere and the gas within the balloon. Mars' atmosphere has such low density that not even a vacuum could support the payload density shown. Spare me doing the maths, because the crater shown is undoubtedly Victoria Crater on Mars. The video animated the exact same image as appears in the Wiki entry for Victoria which is 750 metres across. Not miles, 750m. http://en.wikipedia.org/wiki/Victoria_%28crater%29
So the dirigibles in the video are about 100m long. Compare, for example, the Zeppelin NT in the Wiki: http://en.wikipedia.org/wiki/Zeppelin_NT the size of the gas bag and the size of the payload, even on Earth. Zep NT was 75 meters long.

3/ Gotcha! Or rather Got me! Yes, looking again the rail is going down to a Lunar city on the dark side. I was wrong.

My question remains: would Carl Sagan, romanticist but first and always physicist, have approved these scenes of fictional science, worthy of Kelly Freas?
I think he would have expected better science.

questioner,
the scene in the video at 2:17 shows a hollow cylinder asteroid as you describe, with what might be a fusion reactor down the middle and agriculture on the inner wall. A theoretically possible scenario, given as you say, enough energy, of which there is an abundance in space near stars, and one which I'm sure Sagan would have approved!

John

[Mark Seibold]

I was hoping that others might have identified where the recording of Sagan's voice came from. So I did a search and here it is >
https://www.singularityweblog.com/wande ... wernquist/

-Mark Seibold, Retired IT Specialist, Artist-Astronomer, *My hand sketched pastel art was shown in APOD November 17th, 2006. >
http://apod.nasa.gov/apod/ap061117.html

[Chris Peterson]

1/ Look again. No bungee, just some rock fragments flying off as the thrill seeker jumped out to his death.

We have no way of determining what kind of landing equipment these people might have. Even assuming the surface gravity is high enough to give them a dangerous velocity at the bottom, they could have small thrusters. They could have airbags. There could be cushions at the bottom.

Nothing in this image demonstrates poor physics.

2/Yes, it is difficult to get the scale of those dirigibles, they could be miles long. But then their payloads would be nearly a mile long too. The ratio between balloon and payload size depends strictly on the ratio between the densities of the atmosphere and the gas within the balloon. Mars' atmosphere has such low density that not even a vacuum could support the payload density shown.

You are assuming a high payload density. But all we see in the video is the volume ratio. So again, no blatantly poor physics.

[O. Ehontas]

My question remains: would Carl Sagan, romanticist but first and always physicist, have approved these scenes of fictional science, worthy of Kelly Freas?
I think he would have expected better science.

John

Given that Sagan himself was inspired, in part, by the science fiction stories of life on other planets by Edgar Rice Burroughs and H.G. Wells and later by the "harder" science brought forth by reading Astounding, I think that, taking this film as a fictional visual representation of life in space in the future as an inspiration for future pioneers in space, he would have approved.

[biochemiker]

That video used Carl Sagan's voice, but would he have approved of it's physics content?

1/ Jumping off a high cliff on a low gravity body. Yes, you float down as shown. But gravity is gravity and mass is mass. If your fall was as far as shown, you would still be travelling quite fast at the bottom, with no means of slowing down. Death, from impact or vacuum, unless of course, you had a jet pack. JOhn

On Miranda the gravity is so low that a sufficiently powerful "jet pack" could probably be made out of a properly insulated three-liter bottle of soda stuffed with Mentos. In any case, the cliffs are so high it would take ten minutes to reach the bottom... plenty of time for astronaut Goldie Blox to invent something on her way down.

According to most sources, Verona Rupes is only 5-10 km tall. Assuming 5 kms and an acceleration due to gravity for Miranda of 0.079 m/s², a person would be traveling at approximately 28.1 m/s (63 mph). This isn't terribly fast. Assuming, for simplicity, a 97 kg astronaut in a lightweight pressure suit, it would only require about 8 AeroTech 38mm model 81339 (383.0 N*s impulse, burn time of 7.7 seconds, total weight a bit more than 3 kg) to more than completely negate the velocity of the falling astronaut. The acceleration from the rockets would be a comfortable 0.41 g. More acceleration than a 3L bottle of soda but still not very much. My math or understanding of how impulse works may be wrong; it has been a long time since I took physics. If I've got it wrong, I'd be happy to hear the right answer!

[JohnD]

In theory, biochemiker, in theory.
Steering, stability?
Those guys are falling face down, in the stable position that a free-faller on Earth assumes, stabilised by the atmosphere . How are they to maintain that position? And why? In an upright position, they would see more, more easily and with your rockets, most conveniently strapped to their backs, they could then slow down, as long as they could maintain orientation. Otherwise: https://www.youtube.com/watch?v=g5PoX-jMqZE

This is what happened when skaters strapped rockets to their backs. https://www.youtube.com/watch?v=iCTRjK69Vq8 The last four seconds show what instability will do.

What they need, and I've mentioned it before, is a jetpack! Enough thrust to slow them down, completely steerable, and with some finagling, no doubt some on the way down to maintain orientation. Like this https://www.youtube.com/watch?v=E81KQ7u3-7s

But as it's shown in the video? No way!
John

[biochemiker]

I'm more interested in determining if my math is right. Everything else is engineering (rotation, instability, etc). Given a free falling astronaut/sightseer on Miranda jumping off a 5 km tall Verona Rupes, 1) What is the impact velocity assuming no atmosphere and no deceleration prior to impact? 2) Assuming the astronaut/sightseer has a mass of 100 kg including pressure suit and deceleration mechanism, how much negative acceleration over 5-10 seconds would be needed to achieve a soft landing on the surface of Miranda? To me, it looks like it would only take about $320 worth of model rocket engines to decelerate in 7.7 seconds from approximately 60 mph to soft landing.

A jetpack would be awesome, by the way!

Mike

In theory, biochemiker, in theory.
Steering, stability?
Those guys are falling face down, in the stable position that a free-faller on Earth assumes, stabilised by the atmosphere . How are they to maintain that position? And why? In an upright position, they would see more, more easily and with your rockets, most conveniently strapped to their backs, they could then slow down, as long as they could maintain orientation. Otherwise: https://www.youtube.com/watch?v=g5PoX-jMqZE

This is what happened when skaters strapped rockets to their backs. https://www.youtube.com/watch?v=iCTRjK69Vq8 The last four seconds show what instability will do.

What they need, and I've mentioned it before, is a jetpack! Enough thrust to slow them down, completely steerable, and with some finagling, no doubt some on the way down to maintain orientation. Like this https://www.youtube.com/watch?v=E81KQ7u3-7s

But as it's shown in the video? No way!
John

[BMAONE23]

Crazy of another sort

Click to play embedded YouTube video.

[JohnD]

Mike biochemiker,
The equations I gave in my earlier post:

Time to fall (t) = SQRT(2 x distance/g)
Velocity (v) at end of fall= g x t
Distance (d) fallen = (g x t^2)/2

I'm sure you can work out your example - mine gave me an entertaining five minutes., which I'm glad to repeat.

1/ Time to fall 5km = SQRT(2 x 5000/g) = 354s
Velocity at end of fall = 0.08 x 354 = 28m/s (63mph)

2/ and so on





John

[rstevenson]

Crazy of another sort...

I actually saw something like this -- very definitely not deliberate -- at a sky-diving demonstration back in the 70s here in Halifax. Four skydivers, intending a display of aerial prowess, had dropped over the Commons. The main chute of one of them popped out but failed to fully open. The hundreds of watchers below, including my wife and I, could only stare up in horror as he came down. He maintained a slow spiral motion, flat, with arms and legs wide spread, and managed to hold that posture until he hit, just about 100' feet west of the commons boundary. He was lucky: he hit the 45° slope of a house roof, and bounced off it, coming to rest with his elbows and knees buried in the relatively soft cinder driveway of the house. He broke all sorts of bones, but survived to tell the tale. His compatriots said he did what he could by maintaining that posture, and was lucky that his chute dragging behind helped in keeping his terminal velocity to about 95 mph. Any faster, they said, and he wouldn't have had even a slim chance of survival. He flew and jumped again about a year later!

Rob

[Steve Dutch]

Wonderful video. I presume the five bright stars in the beginning are the visible planets. It's not terribly uncommon to have all five visible at once - once a decade or so. When Jupiter and Saturn get close, they stay close for several years. It's inevitable that the others will get close too at some point.

I'm not totally sure lighter than air craft will work where atmospheric pressure is 1% of Earth's, like in the Mars scene.

The human powered flight on Titan is breathtaking. With a denser atmosphere than Earth, and lower gravity, it might be possible. Maybe the flight units are powered, too.

I hope the jumpers on Miranda have braking jets. Even with that low gravity, and a 15-km fall that would take minutes, it would probably kill you.

The girl at the end is wearing a fur parka and a respirator because all the gas giants have a temperature and pressure zone that's survivable by humans. So she's probably on a floating station like the one in the distance. She doesn't need a spacesuit. She might not even need the parka, but that would probably have challenged viewer suspension of disbelief a bit much.

I love it.