APOD: To Fly Free in Space (2012 Jan 01)

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APOD: To Fly Free in Space (2012 Jan 01)

Postby APOD Robot » Sun Jan 01, 2012 5:06 am

Image To Fly Free in Space

Explanation: At about 100 meters from the cargo bay of the space shuttle Challenger, Bruce McCandless II was farther out than anyone had ever been before. Guided by a Manned Maneuvering Unit (MMU), astronaut McCandless, pictured above, was floating free in space. McCandless and fellow NASA astronaut Robert Stewart were the first to experience such an "untethered space walk" during Space Shuttle mission 41-B in 1984. The MMU works by shooting jets of nitrogen and has since been used to help deploy and retrieve satellites. With a mass over 140 kilograms, an MMU is heavy on Earth, but, like everything, is weightless when drifting in orbit. The MMU was replaced with the SAFER backpack propulsion unit.

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Re: APOD: To Fly Free in Space (2012 Jan 01)

Postby Beyond » Sun Jan 01, 2012 5:13 am

Once again we get to see an Astronaut 'defying' gravity and floating over the purple haze of the essence of Jimmy Hendricks. 8-)
To find the Truth, you must go Beyond.

mihaly

Re: APOD: To Fly Free in Space (2012 Jan 01)

Postby mihaly » Sun Jan 01, 2012 6:44 am

Oh, and indeed it is in fact gravity that was uppermost in my mind.
We say weightless when we speak about situations such as these
but isn't it important to at the same time mention that while weightless
means no dominant force is acting, it is closer to the truth to say that
the astronaut still has mass.
It becomes strange to us mere mortals to imagine such a thing, but when
presented with a picture like this, we often confuse weightless with a
loss of mass.
I often imagine what a group of kids would want to ask about such a
representation: Why hasn't he been drawn to Earth? Why does he not
get drawn to the nearest massive object ie: the shuttle from which the
picture has been taken?

And most importantly: Why should I even believe that this is a real
picture of real things? If I could believe that such a thing is possible
why can I not just jump on the next space shuttle and do it myself?

To which I would have to suggest is both a political and a philosophical
response: Yes, you too can do it, but unfortunately it isn't physically
possible - just yet.
But trust me, this is a real picture of real things, and yes, maybe you too
can do this, with hope, or with more faith in the ability to design and
engineer better space faring and a trust that it isn't always about
MONEY.
Save your mortgage, buy a spaceship.

People pay big $$$ for the sense of weightlessness.
People also pay big $$$ for someone to train you and tell you that
you're too darn FAT.

How wrong thay are.

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Re: APOD: To Fly Free in Space (2012 Jan 01)

Postby Boomer12k » Sun Jan 01, 2012 8:11 am

There is something else you don't see, especially in a still photo. At orbital speed you are going too fast to "fall" to Earth.


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Shez

Re: APOD: To Fly Free in Space (2012 Jan 01)

Postby Shez » Sun Jan 01, 2012 12:46 pm

Hi,

Can I just point out that this pic has been posted three times? Sorry for being finicky!

2009 September 27
2007 September 16
2005 March 22

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Re: APOD: To Fly Free in Space (2012 Jan 01)

Postby orin stepanek » Sun Jan 01, 2012 12:58 pm

Shez wrote:Hi,

Can I just point out that this pic has been posted three times? Sorry for being finicky!

2009 September 27
2007 September 16
2005 March 22

The administration likes a day off also; so like it or not Sundays are repeat days! Nothing wrong with that! It is good to get another look at some of the past pictures and for new members it is a new look! :wink:
Orin

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Re: APOD: To Fly Free in Space (2012 Jan 01)

Postby owlice » Sun Jan 01, 2012 1:51 pm

Q4: Have some APOD pictures been run more than once?
A4: Yes. Many of our readers have been with us less than a year and are unaware of some really spectacular or important astronomy pictures. New information about old pictures is becoming available over the WWW. The text and links for rerun pictures will make use of this newly available information. So although the picture might be old, some of the text and links of each APOD will be new. Also, more web surfers have larger bandwidth connections, which allows us to post higher-resolution image files that can be transferred conveniently. Software to handle more sophisticated image file formats has also become more common, so the picture's size and/or format might be new. Lastly, rerunning APODs saves us time and helps us update our archive. In general, our rerun policy currently is to only rerun APODs more than one year old to keep the pictures relatively "new" to new APOD viewers. We will almost never rerun more than two pictures in any given week. So when you load the current APOD,it is still, most probably, a new picture.

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Re: APOD: To Fly Free in Space (2012 Jan 01)

Postby biddie67 » Sun Jan 01, 2012 2:08 pm

It is certainly a new look to me ~~ I didn't know that the astronauts were trying stuff like this. My heart skips a beat just looking at this, I know I couldn't do it.....

I started wondering about possible phenomenom occuring up there that is analogous to things here on Earth that airplanes and sailboats have to contend with like down drafts, gusts, hidden small tornadoes ~~ disturbances in the solar wind or magnetic fields, even being struck by a micrometerorite .... things that wouldn't disturb the massive ISS but could possibly send a man tumbling head-over-heels.

With apologies for a technically untrained imagination.... but what about the possibiities of some kind of "bow wave" off the front of the ISS knocking the astronaut off course -or- a rogue micro-minnie black hole bumping into him (at the very least that could be one heck of a bruise) ....

Scary adventure.
Last edited by biddie67 on Sun Jan 01, 2012 3:46 pm, edited 2 times in total.

DavidRP

Re: APOD: To Fly Free in Space (2012 Jan 01)

Postby DavidRP » Sun Jan 01, 2012 3:40 pm

Floating free in space? "Drifting" in orbit? Defying gravity? "Going too fast to fall"? I think not on all counts!

This astronaut is whizzing past the clouds below at the tremendous speed of 28,000 kph. Hardly what I would call "floating".

He IS subjected to gravity - about 92% (at his elevation) of what we experience on earth's surface. If he were not, he'd fly off into outer space immediately.

And he is falling at a tremendous rate too. It's just that he's going so fast that, as he falls, the earth curves away below him. If, for instance, the earth was of larger diameter, he'd "sink" down into the atmosphere very quickly. And contacting the atmosphere at 28,000 kph would be a very hot issue! :oops:

And if he were to somehow suddenly reduce his speed from 28,000 kph to zero, he'd plummet toward the ground at tremendous speed, like a skydiver. (Visualize Kirk and the team in the latest Star Trek movie skydiving toward earth to disable the Romulan drill.)

Yes, a very wonderful, spell-binding photo. But lets explain the physics of what's happening.

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Re: APOD: To Fly Free in Space (2012 Jan 01)

Postby biddie67 » Sun Jan 01, 2012 3:55 pm

And thanks to DavidRP (above) for mentioning some of the technical things that have to be very carefully taken into consideration and, hopefully, stay under control so the astronaut could safely return to the ISS. (Not to mention how delicately the ISS is being maintained in orbit.)

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Re: APOD: To Fly Free in Space (2012 Jan 01)

Postby Chris Peterson » Sun Jan 01, 2012 4:02 pm

biddie67 wrote:I started wondering about possible phenomenom occuring up there that is analogous to things here on Earth that airplanes and sailboats have to contend with like down drafts, gusts, hidden small tornadoes ~~ disturbances in the solar wind or magnetic fields, even being struck by a micrometerorite .... things that wouldn't disturb the massive ISS but could possibly send a man tumbling head-over-heels.

With apologies for a technically untrained imagination.... but what about the possibiities of some kind of "bow wave" off the front of the ISS knocking the astronaut off course -or- a rogue micro-minnie black hole bumping into him (at the very least that could be one heck of a bruise) ....

There is some atmosphere where he is floating, so all these effects do exist... but the forces they are capable of exerting are well below the ability of the astronaut to sense (although they might be measured instrumentally). Even a meteoroid wouldn't have much effect on the astronaut's orbit... it would be moving so fast with respect to him that it would blast through like a bullet, transferring hardly any momentum. A bigger meteoroid would vaporize the astronaut completely- I guess you could could call that a disturbance! And a microscopic black hole would pass through the astronaut unnoticed and undetected, leaving no evidence it had been there.
Chris

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Re: APOD: To Fly Free in Space (2012 Jan 01)

Postby moonstruck » Sun Jan 01, 2012 5:19 pm

Wow! That's amazing. Just curious, if he threw a ball straight out would it go a few hundred yards and just stop or would it come back around in an hour and a half or so, and hit him in the back of the head? I know this is a silly question, but my curious mind would really like to know. :?

Tszaeau

Re: APOD: To Fly Free in Space (2012 Jan 01)

Postby Tszaeau » Sun Jan 01, 2012 7:48 pm

moonstruck wrote:Wow! That's amazing. Just curious, if he threw a ball straight out would it go a few hundred yards and just stop or would it come back around in an hour and a half or so, and hit him in the back of the head? I know this is a silly question, but my curious mind would really like to know. :?


My guess is that if he threw the ball forward in the direction of his orbit, he'd lose forward momentum equal to whatever feeble momentum he imparted to the ball. The resulting pitch would be so weak and slow it probably wouldn't go far from him and then just drift slowly down. If he was able to maintain his orbit, with his power pack, the ball would not.

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Re: APOD: To Fly Free in Space (2012 Jan 01)

Postby eltodesukane » Sun Jan 01, 2012 9:48 pm

DavidRP wrote:Floating free in space? "Drifting" in orbit? Defying gravity? "Going too fast to fall"? I think not on all counts!
...
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There are three kinds of people in this world; those who can count, and those who can't.

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Re: APOD: To Fly Free in Space (2012 Jan 01)

Postby Chris Peterson » Mon Jan 02, 2012 12:01 am

moonstruck wrote:Wow! That's amazing. Just curious, if he threw a ball straight out would it go a few hundred yards and just stop or would it come back around in an hour and a half or so, and hit him in the back of the head? I know this is a silly question, but my curious mind would really like to know. :?

When he throws the ball, he simply puts it into a slightly different orbit than he is in himself. Depending on the direction of his toss, it will end up in either a slightly higher (slower) orbit, or a slightly lower (faster) orbit. So he and the ball will slowly draw apart. But they'll still be close together for a long time... it will take many orbits for one to lap the other.
Chris

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Re: APOD: To Fly Free in Space (2012 Jan 01)

Postby DavidLeodis » Mon Jan 02, 2012 1:11 pm

I love the image. I'm sure there would be some apprehension while out there but it must be a tremendous feeling to actually be doing it. 8-)

Mind you, I wonder if there was another astronaut out there if he/she would 'sit' in front and so spoil the view like what does sometimes happen in a cinema. :roll:

troffer

Re: APOD: To Fly Free in Space (2012 Jan 01)

Postby troffer » Fri Jan 13, 2012 6:48 pm

Zoomed in on the astronaut, what is the constellation looking thing to the right of the astronaut? Hair or lint? I thought space missions were cleaner than that...

Its weird that it looks like a star-map constellation with the lines. That or maybe software was used to create this photo =)

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Re: APOD: To Fly Free in Space (2012 Jan 01)

Postby Chris Peterson » Fri Jan 13, 2012 6:58 pm

troffer wrote:Zoomed in on the astronaut, what is the constellation looking thing to the right of the astronaut? Hair or lint? I thought space missions were cleaner than that...

Looks like a bit of lint on the sensor, which shows up brighter than the background because of dark frame or flat field calibration procedures. If you push up the contrast, you can see dust, cosmic ray hits, stars, and various artifacts.

Space missions are not typically all that clean. Certain parts of various instruments are maintained in as clean as possible state, but you can bet that it's plenty dusty inside the ISS (most dust is dead human skin), and the cameras used by the astronauts for shots like this one are ordinary consumer cameras that are probably no cleaner inside than your own.
Chris

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Re: APOD: To Fly Free in Space (2012 Jan 01)

Postby bystander » Sun Feb 12, 2012 9:50 pm

Far Above the World
Universe Today | Jason Major | 2012 Feb 12
28 years ago today, NASA astronaut Bruce McCandless left the relative safety of Challenger’s payload bay and went untethered into orbit around Earth, venturing farther than anyone ever before.

The historic photo above was taken when McCandless was 320 feet from the orbiter — about the length of an American football field, or just shy of the width of the International Space Station.

The free-flying endeavor was possible because of McCandless’ nitrogen-powered jet-propelled backpack, called a Manned Maneuvering Unit (MMU). It attached to the space suit’s life-support system and was operated by hand controls, allowing untethered access to otherwise inaccessible areas of the orbiter and was also used in the deployment, service and retrieval of satellites.

The MMU used a non-contaminating nitrogen propellant that could be recharged in the orbiter. It weighed 140 kg (308 lbs) and has a built-in 35mm camera.

After the Challenger disaster, the MMU was deemed too risky and was discontinued. But for a brief period of time in the early ’80s, humans had the means for really “soaring to new heights”.
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BrownProject

Re: APOD: To Fly Free in Space (2012 Jan 01)

Postby BrownProject » Thu Jan 10, 2013 11:42 pm

if there is no air in space, then how can a propullsion pack, shooting out nitrogen change your direction? If it ejects from the pack, but pushes on nothing, then how do you steer? I always thought things like the moon shoot relied on mathmaticle equations to find the proper perablas to whip you around the moons gravity, and bing off in calculation, or execution, being off by a few millimeters on earth launch means being off by miles at the moon type of situation. You can actually change your direction in space? You are not relient on just gravitational forces? if there is 'nothing' in space, what does the propulsion push against to change direction? Thanks for any insight. i really appreciate it.

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Re: APOD: To Fly Free in Space (2012 Jan 01)

Postby Chris Peterson » Thu Jan 10, 2013 11:55 pm

BrownProject wrote:if there is no air in space, then how can a propullsion pack, shooting out nitrogen change your direction? If it ejects from the pack, but pushes on nothing, then how do you steer? I always thought things like the moon shoot relied on mathmaticle equations to find the proper perablas to whip you around the moons gravity, and bing off in calculation, or execution, being off by a few millimeters on earth launch means being off by miles at the moon type of situation. You can actually change your direction in space? You are not relient on just gravitational forces? if there is 'nothing' in space, what does the propulsion push against to change direction? Thanks for any insight. i really appreciate it.

Rockets work on the principle established by Newton's Third Law, which states that for every action there is an equal and opposite reaction. They do not work by pushing against atmosphere. Indeed, any atmosphere simply serves to reduce efficiency. Rockets are typically at their most efficient in a vacuum.
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BrownProject

Re: APOD: To Fly Free in Space (2012 Jan 01)

Postby BrownProject » Fri Jan 11, 2013 12:11 am

Chris Peterson wrote:Rockets work on the principle established by Newton's Third Law, which states that for every action there is an equal and opposite reaction. They do not work by pushing against atmosphere. Indeed, any atmosphere simply serves to reduce efficiency. Rockets are typically at their most efficient in a vacuum.


fascinating. so with the right equipment, space travel can be highly accurate, like flying a plane on earth. Amazing. Thanks for the explanation. Learn something new every day.


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