Profile cover photo
Profile photo
Martin Peverley
1,754 followers -
IT guy, firefighter, family man.
IT guy, firefighter, family man.

1,754 followers
About
Martin's posts

Post has shared content
Earth orbit isn't so much "high" as "fast." The ISS routinely passes closer to my house than Los Angeles; it wouldn't be a terribly far commute. The only problem is that, if I were to travel in a straight line those 249 miles up to touch it, I would then simply be 249 miles above the ground, and what would happen next is technically known as "falling."

Things stay in orbit not by being high up, but by moving fast enough that they continually fall towards the ground and miss. Draw a line between yourself and the center of the Earth; gravity is pulling you along that line. Point your nose perpendicular to that line, and go: your normal straight-line motion is moving you away from the Earth. The art of orbiting is simply the art of keeping those two things in balance, so that you're moving so quickly through space that you're losing altitude through falling at the same speed that you're gaining it through hurtling.

Of course, you have to be going kind of fast for this to work. The ISS travels at a steady speed of 7.6km (4.76 miles) per second. 

This is why spacecraft don't simply fly straight up; they fly up about 26,000' to get out of the thickest part of the air, then turn 90° and thrust for speed. (This post talks more about why that makes more sense than taking off horizontally like an airplane: https://plus.google.com/+YonatanZunger/posts/VsYyUDxFUDr

It probably won't surprise you that when you're flying at this speed, running into things is not a good idea. The picture below is from a test run by the ESA (the European Space Administration) of a "hypervelocity impact." The block is made of solid Aluminum, and was cut in half after the test to see what happened. The pellet is not the one that was used in the test; you can see parts of the pellet used in the test in the form of those smears along the inside of the crater. At 6.8km/s, the impact blew the crater you see into the block of metal, and the shock wave in front of it opened up that second cavity at the bottom.

Note that the speed here was only 6.8km/s. Oribtal speed is a function of altitude alone; anything flying at the ISS' altitude will be going at 7.6km/s. But it might be going the other way, which means that collisions with random debris in orbit could happen at speeds as high as 15km/s. Meteoroids coming in from elsewhere in the solar system could be flying as fast as 72km/s.

The ESA's page (http://www.esa.int/Our_Activities/Operations/Space_Debris/Hypervelocity_impacts_and_protecting_spacecraft) about these hypervelocity impact tests is full of wonderful understatements. An impact of any 10cm object against any spacecraft would "most likely entail a catastrophic disintegration of the target." (I should say that space travel includes phrases like "hard start" for what happens when fuel and oxidizer accumulate in a rocket engine's chamber before the engine ignites, and "spontaneous disassembly" for what happens if the airframe is separated into multiple pieces on an unscheduled basis. For those outside the field, those translate as "the engine explodes" and "the spacecraft explodes," respectively)

The thing I keep thinking about when I see this picture is imagining being aboard a spacecraft – especially something big, like the ISS – and hearing a loud "bang" resonating throughout the ship. That's all you would know at first: something, somewhere aboard, just caused the entire ship to shake.

Space travel is not for the faint of heart.
Photo

Post has attachment
PhotoPhotoPhotoPhotoPhoto
Wine
20 Photos - View album

Post has attachment

Just searched and found this, as we too were stung by the Ultraviolet issue. Off to download, and thanks, Disney!!

Post has attachment
Playing with my new #GoPro, trying to get shots of the dog, and just happened to get this.

#SelfySunday
Photo

Post has attachment

Great How-To, saved me a bunch of time.

Post has attachment

From my colleagues on the other side of the pond...

AN ENGINEERING PERSPECTIVE ON CHRISTMAS

There are approximately two billion children in the world.
If Santa does not visit children of non Christian religions, this reduces the workload for Christmas night to 15% of the total, or 378 million. (And surely a case for the race relations board to consider)

At an average rate of, say, 3.5 children per household, that comes to 108 million homes, presuming there is at least one good child in each. (Again, surely a case to answer under human rights law) Santa has about 31 hours of Christmas to work with, thanks to the different time zones and the rotation of the earth, assuming east to west, which seems logical. (Surely a case under employment law). This works out to 967.7 visits per second.

This is to say that for each Christian household with a good child, Santa has around 1/1000th of a second to park the sleigh, hop out, jump down the chimney, fill the stocking, distribute the remaining presents under the tree, have whatever snacks and drinks have been left for him, get back up the chimney, jump into the sleigh and get onto the next house. (Surely a case under drink driving law, does that apply to sleighs?)

Assuming that each of these 108 million stops is evenly distributed around the earth (which, of course, we know to be false, but will accept for the purposes of our calculations), we are now talking about 0.78 miles per household; a total trip of 75.5 million miles, not counting bathroom stops or breaks.
This means Santa's sleigh is moving at 650 miles per second -- 3,000 times the speed of sound. (Surely a case under aviation law). For purposes of comparison, the fastest man-made vehicle, the Ulysses space probe, moves at a poky 27.4 miles per second, and a conventional reindeer can run (at best) 15 miles per hour.

The payload of the sleigh adds another interesting element. Assuming that each child gets nothing more than a medium sized LEGO set (two pounds), the sleigh is carrying over 500 thousand tons, not counting Santa himself. Assume that on land, a conventional reindeer can pull about 300 pounds. Even granting that the "flying" reindeer can pull 10 times the normal amount, the job can't be done with eight or even nine of them -- Santa would need 360,000 of them. (Surely a case that the RSPCA should investigate) This increases the payload, not counting the weight of the sleigh, another 54,000 tons, or roughly seven times the weight of the Queen Elizabeth (the ship, not the monarch).

600,000 tons traveling at 650 miles per second creates enormous air resistance - this would heat up the reindeer in the same fashion as a spacecraft re-entering the earth's atmosphere. The lead pair of reindeer would absorb 14.3 quintillion joules of energy per second each. In short, they would burst into flames almost instantaneously, exposing the reindeer behind them and creating deafening sonic booms in their wake. (Definitely a case for the RSPCA)
The entire reindeer team would be vaporized within 4.26 thousandths of a second, or right about the time Santa reached the fifth house on his trip.

Not that it matters, however, since Santa, as a result of accelerating from a dead stop to 650 miles per second in .001 seconds, would be subjected to acceleration forces of 17,000 G's. An 18 stone Santa (which seems ludicrously slim) would be pinned to the back of the sleigh by 2,000 tonnes of force, instantly crushing his bones and organs and reducing him to a quivering blob of pink goo.
The whole thing is surely a case under the laws of physics!

Merry Christmas to all!

Post has shared content
A little too long and a little too nerdy to post anywhere but the server room; excellent, nonetheless.
Genesis Take Two: The Birth of Geekdom

1. In the beginning GOD created the Bit and the Byte. And from those he created the Word.

2. And there were two Bytes in the Word; and nothing else existed. And God separated the One from the Zero; and he saw it was good.

3. And God said - Let the Data be; And so it happened. And God said  Let the Data go to their proper places. And he created floppy disks and hard disks and compact disks.

4. And God said - Let the computers be, so there would be a place to put floppy disks and hard disks and compact disks. Thus God created computers and called them hardware.

5. And there was no Software yet. But God created programs; small and big... And told them - Go and multiply yourselves and fill all the Memory.

6. And God said -I will create the Programmer; And the Programmer will make new programs and govern over the computers and programs and Data.

7. And God created the Programmer; and put him at Data Center; And God showed the Programmer the Catalog Tree and said You can use all the volumes and subvolumes but DO NOT USE Windows.

8. And God said - It is not Good for the programmer to be alone. He took a bone from the Programmer's body and created a creature that would look up at the Programmer; and admire the Programmer; and love the things the Programmer does; And God called the creature: the User.

9. And the Programmer and the User were left under the naked DOS and it was Good.

10. But Bill was smarter than all the other creatures of God. And Bill said to the User - Did God really tell you not to run any programs ?

11. And the User answered - God told us that we can use every program and every piece of Data but told us not to run Windows or we will die.

12. And Bill said to the User - How can you talk about something you did not even try. The moment you run Windows you will become equal to God. You will be able to create anything you like by a simple click of your mouse.

13. And the User saw that the fruits of the Windows were nicer and easier to use. And the User saw that any knowledge was useless - since Windows could replace it.

14. So the User installed the Windows on his computer; and said to the Programmers that it was good.

15. And the Programmer immediately started to look for new drivers.

And God asked him - What are you looking for? And the Programmer answered - I am looking for new drivers because I can not find them in the DOS. And God said - Who told you need drivers? Did you run Windows?

And the Programmer said - It was Bill who told us to !

16. And God said to Bill - Because of what you did you will be hated by all the creatures. And the User will always be unhappy with you.

And you will always sell Windows.

17. And God said to the User - Because of what you did, the Windows will disappoint you and eat up all your Resources; and you will have to use lousy programs; and you will always rely on the Programmers help.

18. And God said to the Programmer - Because you listened to the User you will never be happy. All your programs will have errors and you will have to fix them and fix them to the end of time.

19. And God threw them out of the Data Center and locked the door and secured it with a password.

20. GENERAL PROTECTION FAULT

Unknown
Photo

Post has shared content
Love it, should do a "candy disposal" for the 6 y.o.

Post has shared content
Would love to see Top Gear UK do this "How hard could it be?".
Do not adjust your Internet, this upside down Camaro is real ... Dvice - "Yes that car is upside down, and yes it's taking part in a race. The race is a tongue-in-cheek event called the 24 Hours of LeMONS, an endurance race for $500 cars. The car in question can at once be described as a Chevy and a Ford, a Camaro and a Festiva, right side up and upside down.

The man behind this Frankenstein's monster of a vehicle is himself quite the character. Going by the moniker Speedycop, the car's creator has transplanted the body of the Camaro (upside down) onto the guts of the Festiva — meaning that, yes, this Camaro has a four cylinder, 1.3 liter engine.

Needless to say, the upside down car didn't exactly cross the finish line first. Nonetheless, as a street car, this sucker is sure to garner a well deserved stare or two. Check out the video below to see it in all it's racing glory. ..."

more including videohttp://bit.ly/14XTSvk
Photo
Wait while more posts are being loaded