Slashdot Mirror
SpaceX Cargo Capsule Leaves Space Station For Home
An anonymous reader writes "The commercial cargo ship Dragon left the International Space Station, and is heading home with nearly two tons of science experiments and old equipment. From the article: 'The unpiloted Dragon departed the International Space Station at 9:26 a.m. EDT to begin a trip expected to culminate just after 3 p.m. with a parachute-assisted splashdown in the Pacific Ocean, about 300 miles west of Baja California. NASA astronaut and station commander Steve Swanson controlled a 58-foot robotic arm that pulled the Dragon from its Harmony node port at 8 a.m., then released the capsule into space 266 miles over the ocean south of Australia.'"
Splashdown. Status below -
http://spaceflightnow.com/falc...
It could be worse, it could be Monday.
Shut up.
quote>Why would they use a measure of WEIGHT instead of a measure of MASS?
Ton is already ambiguous, but since it is a USA media article, its safe to assume that they meant what is also known as the short ton, or 2000 pounds. The pound is defined as 0.45359237 kg, so it is, by definition, a unit of mass.
So NASA spent $1.6 billion for the CRS program, that is for 12 missions [1]. That is $75 million for mission. The payload of the CRS-3 mission, the biggest so far by the way, was 4,605 pounds (the declared maximum is 7,300 lb)[2], in other words $16,200 for pound of payload, including packaging. I'd like to know how does that compare to other space transport services.
So people who drive cars, and therefore use public transportation less or not at all, should pay more so that people who do use the system pay less?
More likely someone doesn't know that there is a difference between a Ton and a Tonne, and figures they're just the british and american ways of spelling the same thing. The dragon capsule is rated to return up to 2500kg of mass to the earth, so it stands to reason that this is just a lack of pedantry on the part of the author.
...si hoc legere nimium eruditionis habes...
Don't normally reply to myself, but that was a Cut and paste out of another article here. :)
...si hoc legere nimium eruditionis habes...
Also, they say the capsule is 12 feet in diameter. I would prefer to know the circumference area in micro-hectares.
A pound is a unit of weight and can correspond to any kg mass, determined by the gravity of the place where it is being measured. Weight is dependent on gravity, mass is not. Welcome to 5th grade science class
All your 09 F9 11 02 9D 74 E3 5B D8 41 56 C5 63 56 88 C0 are belong to us
Pounds are both a measure of weight and mass, and the USA Today article uses pounds (not tons, Slashdot did that conversion) because, for better or worse, the US population is more familiar with US customary units than metric units, and USA Today is marketed at a US audience (the name is a bit of a clue). NASA also uses US units for some mind-baffling reason (maybe it likes destroying Mars Orbiter missions?) so the US units make sense in this story.
"None can love freedom heartily, but good men; the rest love not freedom, but license." --John Milton
I would prefer to know the circumference area in micro-hectares.
What, you figure they could reduce costs by growing space cabbage on it?
Ezekiel 23:20
A pound is a unit of weight and can correspond to any kg mass, determined by the gravity of the place where it is being measured.
Weight is dependent on gravity, mass is not. Welcome to 5th grade science class
Which is why the metric system has separate units for mass and weight/force.
But that's not the case with the pound, it is used for both (sometimes, but not always more specifically as pound-force or pound-mass)
http://en.wikipedia.org/wiki/P...
The pound or pound-mass (abbreviations: lb, lbm, lbm, [1]) is a unit of mass used in the imperial, United States customary and other systems of measurement. A number of different definitions have been used, the most common today being the international avoirdupois pound which is legally defined as exactly 0.45359237 kilograms, and which is divided into 16 avoirdupois ounces.
Don't believe Wikipedia? How about the NIST?
http://physics.nist.gov/Pubs/S...
MASS and MOMENT OF INERTIA: To convert from pound (avoirdupois) (lb) to kilogram (kg)
http://physics.nist.gov/Pubs/S...
FORCE: To convert from pound-force (lbf) to newton (N)
The real world is not always as simple as what you learned in 5th grade science, when your teacher said "The pound is a unit of weight, not mass", he was correct and incorrect at the same time due to the ambiguous nature of the unit.
That is two metric tons or in other words about 2000 kg. 1000 kg == 1 metric ton, which is also about 2200 lbs or roughly close to a standard "short ton".
But it still is measuring mass.
With spaceflight (and SpaceX specs) it is metric tons.... but still about the same amount of mass/weight.
Because nearly everyone forgets about the slug.
> "from its Harmony node"
Man, Buffy the Vampire Slayer has some powerful fans.
(-1: Post disagrees with my already-settled worldview) is not a valid mod option.
People landed on the Moon with pounds, feet, gallons, and other "Imperial" measurement units. It is possible to do these things and not need the Metric system. Hell, they landed on the Moon using slide rules which performed most of the calculations and for those things that needed faster computations, NASA needed to invent a real-time operating system (something that didn't even exist prior to NASA's use of the OS).
Don't get me started on how silly the metric system is too. It has its use and is widely used, but it also has a number of limitations and shortcomings. I certainly wouldn't blame the crash of the Mars Orbiter strictly on a supposed backwardness of NASA engineers because they happen to use different units than the ones you apparently are used to using.
Well we can probably assume that they meant the equivalent weight on the surface of Earth, since otherwise it would be a meaningless number.
So you'd prefer it if they converted the circumference from feet to square feet, then from square feet to square decimeters?
"I do not agree with what you say, but I will defend to the death your right to say it"
But that's not the case with the pound, it is used for both (sometimes, but not always more specifically as pound-force or pound-mass)
Theres a;so the pound sterling £ which is metric. It used to be Imperial (pounds, shillings and pence)
They should stop using the term 'metric ton' . A thousand kilograms is a megagram
The problem with metric is that some of the arbitrary base units are more difficult for humans to estimate and use. For example, let us take some common units of measure: centimetres are too small, decimetres are too large. Both are inferior for human estimation compared to inches. An inch can be approximated more easily using say a segment of a finger. Even feet are easier for a lot of people to estimate than metres (or yards). Especially for in-between distances that are neither small nor large. In general the idea of using orders of magnitude prefixes is a great idea, but the base unit, metres, leaves something to be desired. And lets not kid ourselves. All units of measure are arbitrary. A metre is an arbitrary length. It's currently based on some reference bar somewhere. It may have originated by dividing latitudinal distance by some factor or something, but the standard metre is completely and utterly arbitrary. We could have selected some other unit like an inch to be the base and everything would be fine, though a kilometre would be very small.
But since pounds is only used in the brittish empire and because that have become so small by now does it really matter any more? ;D
Everywhere it matters we'd use newton and kilograms anyway.
Just limit the usage of pounds into the queens closet already.
The term "ton" is widely used by many cultures and is a hold-over from earlier mass-weight units. If you want to call it a megagram, that is your call, but the widespread and common usage is still "metric ton" by both governments and especially industrial users. If you want to put on blindfolds and pretend that such units don't exist, that is your own problem and you will be laughed out of many conferences by being such a stupid stick in the mud about such silly things.
Go ahead and be a purist if you want, the rest of the world will continue to exist and go on its merry way. Complaining on Slashdot isn't going to change the world either.
The only real units IMHO are Plank units, but even those aren't useful for practical everyday applications.
BTW, you don't need to worry about unit conversions unless you are using different subsystems from different countries or manufacturers that aren't using the same units. It really doesn't matter what you are using even if it is centifurlonghs per microfortnights for velocity. While done as more or less a practical joke, the microfortnight was used by VMS in its timing circuits and used for various accounting purposes. It shows up in MS Windows as a portion of the VMS thread accounting system is a part of the kernel (under license from DEC from a long time ago).
You guys are just crazy
It is a mass that accelerates by 1 ft/s2 when a force of one pound-force (lbF) is exerted on it. One slug has a mass of 32.174049 lbm or 14.593903 kg based on standard gravity, the international foot, and the avoirdupois pound
So to avoid the confusion between lbm and lbf, you make a new unit of mass that converts to the other unit of mass with the easy to remember value of 32.174049! Brilliant!
"metric ton"?
ITYM tonne.
Watch this Heartland Institute video
And 1000km should be 1 megameter.
Oolite: Elite-like game. For Mac, Linux and Windows
I don't find metric any more difficult to estimate or use. I use both metric and imperial units every day, and your message is the first time I've ever seen anyone saying a centimeter is hard to estimate. I find estimating stuff in cm no more difficult than doing the same in inches.
Where metric wins *massively* is when you're having to deal with using lots of different types of measures, such as estimating things such as power requirements, energy requirements and that kind of thing because the units are designed to work with each other and are all base-10. Imperial measures are all base something-random (for instance, with weight the common things are divisions of 16, eg 16 oz in 1 lb, but in distance it's something else, 12 in to 1 foot, 3 feet to 1 yard, 1760 yards to one mile) making it absurdly difficult to do mental estimations of things involving the different units because of all the arbitrary conversion factors you end up needing. You must admit that 1000 meters = 1km is a lot easier to remember and use than 1760 yards to 1 mile. You can work out instantly how many meters a distance of 1.75km is, but not so easy to mentally figure out how many yards in 1.75 miles. OK, a trivial example that's probably not what a lot of people do every day, but just consider some things in engineering - mentally estimating the number of joules a capacitor can store at a given voltage is much easier than doing it in calories because you don't need to stick an arbitrary-seeming conversion factor into the process if you're doing it all in SI units. The lack of consistency in imperial units means you're having to do this all the time and this makes it a lot more error prone.
Oolite: Elite-like game. For Mac, Linux and Windows
The word "pound" can refer to mass, weight, or currency. To disambiguate, terms such as "pound-force", "pound-mass" and "Pound sterling" can be used instead, but otherwise the meaning is often clear in context. In particular, the ton is defined in terms of the pound-mass (2000lb or 2240lb, depending on who you ask), although officially the various "ton" units are defined in terms of the kilogram - also a unit of mass. And of course, the metric ton is 1000kg.
True - that's the term consistent with the current SI definitions, but I'd personally prefer calling it a kilograv :p