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Golf in Space
deeptrace writes "Tentatively scheduled for a spacewalk this summer, a Russian cosmonaut will take his trusty six iron and a special weightless-friendly tee and put a golf ball into orbit from outside the International Space Station. The golf ball has an embedded transmitter so that it can be tracked as it orbits. It is expected to orbit for 3 to 4 years before burning up on re-entry. The golf shot is the result of promotional fees paid to the Russian space agency by a Canadian golf club manufacturer."
is another piece of slightly-too-small-to-track, large-enough-to-annihilite-your-windshield piece of 23,000 MPH space junk to worry about.
Cheers,
Ian
(1) how fast can you swing IN A FREAKING SPACESUIT?
(2) the speed of the space junk will be the speed of the space station, +/- the speed of your swing (see (1))
(3) there is a very thin atmosthere at low earth orbit deteriorating the orbit of anything there, further slowing the golf ball with time
(4) due to the nature of the spin of the earth and the fact that you get a boost from it, all spacecraft are launched in the same direction.
(5) therefore any collosion with the golfball at a later time will be at a velocity SLOWER than the swing, far slower than any other piece of space junk out there, and definitely not a threat. Not to mention there is a TRANSMITTER in there. They will see it coming and wave
Not only does it contain a transmitter, but the article says it will burn up on re-entry in 3 to 4 years.
The odds of this being a problem for 'space entrepreneurs' is probably comparable to me winning powerball within the same timeframe. Space is big. Really big.
"So I wonder how many yards it will travel in 3 or 4 years before it burns up? This is going to be the longest drive ever."
/.</sarcasm> - that's 3696 billion yards.
From TFA:
"The ball is expected to travel up to 2.1 billion miles before it drops back into the atmosphere and burns up."
<sarcasm>I know it's a really hard conversion, especially for the techie crowd on
Time is an illusion. Lunchtime doubly so. - Douglas Adams
Calling out 'Fore!' let him know to keep an eye out for the ball.
Nowadays, it just kinda means 'duck!' though :)
ok, from TFA:
"The ball is expected to remain in orbit for three to four years."
"The ball is expected to travel up to 2.1 billion miles before it drops back into the atmosphere and burns up."
TFA doesn't say if that distance is based on 3 or 4 years, so I'll work out both and give a max & min average velocity:
Min time in space = 3 years = 1,096 days (2*365 + 1*366: leap year in 2008) = 26,304 hours
Max time in space = 4 years = 1,461 days (3*365 + 1*366: leap year in 2008) = 35,064 hours
2.1 billion miles / 26,304 hours = 79,835.77 mph
2.1 billion miles / 35,064 hours = 59,890.49 mph
So the average speed will be between 59,890.49 mph & 79,835.77 mph!! (or 96,384.16 kph & 128,482.90 kph)
Considering the speed of sound (at sea level) is 761mph it's just as well in space nobody can here you play golf!
Haydn.
Time is an illusion. Lunchtime doubly so. - Douglas Adams
I'd worry less about the golf ball and more about the embarrassed cosmonaut who's trying to push the divot he just made back in to the ISS with the toe of his spacesuit before anyone notices.
Well, I'm an aerospace engineer also. The difference is that I happen to know a bit about orbit geometry, space debris, and most importantly relative motion.
This is a stupid "experiment". That transmitter will likely last days at best. In any case, the USAF which maintains the most complete and widely used space catalog does not & cannot use that transmitter to track the object. They rely exclusively on radar & optical observations to maintain the catalog. And this object is to small to be reliably tracked by the existing sensors unless they've stuck some dipoles on it as they have with other microsat experiments - and even then it's something of a crapshoot. Didn't sound like it from the article. Even if you could track it, most stuff up there doesn't have the ability to manuever to get out of the way even if they did see it coming. And almost nobody would see it coming because almost nobody does any form of collision avoidance analysis.
So, back to orbits. First, there are some retrograde satellites. Israel in particular doesn't have much of a launch azimuth beyond almost due west down the mediteranean. So you end up with stuff like OFEQ 5 (27434, 2002-025A) with an inclination of about 144 degrees.
But you don't need to pick out oddballs OFEQ 5 and a handful of other to see the problem. For the moment, we'll ignore eccentricity and right ascension of ascending node and focus on inclination only (ie. the collision occurs at the equator), since that's the most intuitive point to illustrate here.
ISS (25544, 1998-067A) has an inclination of 51.6 degrees. We'll assume the inclination of "GolfSat" is about the same, since it takes *alot* of energy to change the orbital plane significantly. A quick search of the catalog shows there are 344 objects crossing the orbit of ISS with inclinations ranging from 0.55 degrees (28645, 2005-015B, BLOCK DM-SL R/B) to 97 degrees (27551, 2002-049B, CZ-4B R/B).
So the inclination difference between ISS and 27551 is about 51 degrees. Let's call the velocity of each object 7 Km/second to keep it simple. The relative velocity of a collision between these objects would be approximately 6 Km/second. I'll leave the trig as an exercise for the reader.
By comparison, the muzzle velocity of a rifle bullet tops out around 1 Km/second. Taking that as the lower bound of risk, that gives us a inclination difference of just 8 degrees to give GolfSat a relative velocity equal to that of a rifle bullet.
Of course, inclination isn't the only thing playing as I mentioned before. It's not hard to arrange the orbit geometry such that the angle of incidence at collision is significantly > 90 degrees - ie. getting toward head on.
So, in short, you don't need anything like "reciprocal orbits" to end up with enormously high relative velocities.