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## SpaceX Cargo Capsule Leaves Space Station For Home56

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.'"
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## SpaceX Cargo Capsule Leaves Space Station For Home

• #### Slashdown confirmed (Score:5, Informative)

on Sunday May 18, 2014 @03:13PM (#47033135)

Splashdown. Status below -

http://spaceflightnow.com/falc... [spaceflightnow.com]

• #### 2 tons? (Score:1)

Why would they use a measure of WEIGHT instead of a measure of MASS?
• #### Re: (Score:2, Insightful)

by Anonymous Coward

Shut up.

• #### Re: (Score:2)

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.

• #### Re: 2 tons? (Score:2)

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
• #### Re: (Score:3)

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... [wikipedia.org]

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... [nist.gov]

MASS and MOMENT OF INERTIA: To convert from pound (avoirdupois) (lb) to kilogram (kg)

http://physics.nist.gov/Pubs/S... [nist.gov]

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.

• #### Re: (Score:2)

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)

• #### Re: (Score:1)

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.

• #### Re: (Score:2)

Well we can probably assume that they meant the equivalent weight on the surface of Earth, since otherwise it would be a meaningless number.
• #### Re: (Score:2)

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.

• #### Re: (Score:2)

With spaceflight (and SpaceX specs) it is metric tons.... but still about the same amount of mass/weight.

• #### Re: (Score:2)

They should stop using the term 'metric ton' . A thousand kilograms is a megagram

• #### Re: (Score:2)

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

• #### Re: (Score:1)

"metric ton"?

ITYM tonne.

• #### Re: (Score:2)

And 1000km should be 1 megameter.

• #### Re: (Score:2)

True - that's the term consistent with the current SI definitions, but I'd personally prefer calling it a kilograv :p

• #### Re: (Score:2)

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.

• #### Re: (Score:2)

Don't normally reply to myself, but that was a Cut and paste out of another article here. :)

• #### Re: (Score:3, Funny)

Also, they say the capsule is 12 feet in diameter. I would prefer to know the circumference area in micro-hectares.
• #### Re: (Score:2)

I would prefer to know the circumference area in micro-hectares.

What, you figure they could reduce costs by growing space cabbage on it?

• #### Re: (Score:2)

Also, they say the capsule is 12 feet in diameter. I would prefer to know the circumference area in micro-hectares.

So you'd prefer it if they converted the circumference from feet to square feet, then from square feet to square decimeters?

• #### Re: (Score:2)

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 [wikipedia.org] missions?) so the US units make sense in this story.

• #### Re: (Score:2)

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 u

• #### Re: (Score:2)

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.

• #### Re: (Score:1)

Because nearly everyone forgets about the slug [wikipedia.org].

• #### Some calculations (Score:2)

So NASA spent \$1.6 billion for the CRS program, that is for 12 missions [1] [wikipedia.org]. 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] [nasaspaceflight.com], 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.
• #### Re: (Score:1)

Since there is currently no other craft available that can bring stuff back, this is pointless. Later Musks plan is to reuse all the components, which should bring the cost down a lot.
• #### Re: (Score:2)

The COTS program never even required hauling cargo back from orbit. The contract was strictly for sending stuff up to the ISS, not for returning anything (which is why the Cygnus spacecraft doesn't have re-entry capabilities). SpaceX threw the re-entry capabilities on as an extra and offered it to NASA,which NASA is certainly using.

That the Dragon is the only vehicle currently in production which is capable of returning more than a hundred kilograms of stuff from orbit (that is the Soyuz spacecraft, where

• #### Re:Some calculations (Score:5, Interesting)

<baldur.norddahl@gmail.com> on Sunday May 18, 2014 @04:50PM (#47033655)

The space shuttle was \$450 million per mission not including development costs. That would lift 24 ton and a lot of volume to ISS. That was good for building the space station but perhaps overkill for the maintenance. They are not even using the full capability of the Dragon spacecraft.

The Dragon will only move 3.3 ton to the ISS. If you only count weight by dollar this is more expensive than a Space Shuttle launch. On the other hand you will get much more frequent deliveries which may be what is needed now.

If you count development costs, each Space Shuttle launch was 1.5 billion USD. Viewed this way, the CRS program for Space X is just one shuttle. And perhaps this is the correct way to do the accounting considering that the 1.6 billion that Space X receives also has to cover their development costs. I would expect that they can give a good discount on future launches, should NASA want more than 12.

• #### Re: (Score:2)

Better than just discounting once development is paid off, actually... part of that R&D investment is into making the first stage, the Falcon 9 booster, re-usable. Currently they are single-use and amount to 70% of SpaceX's costs per launch. A reusable first stage would let SpaceX cut their costs by a tremendous margin.

It's really astonishing how much SpaceX is achieving with the budget they have. The space shuttle may have been a technological marvel in terms of capabilities, but it was unreliable, exp

• #### Re: (Score:2, Informative)

by Anonymous Coward

Should be noted that the capsule was physically full. It could have carried more mass but the average density of the cargo isn't that high so it would seem that it could've taken more up while in fact it took a full load.

When resupplying the ISS, it is not all about up/downmass. Physical dimensions also matter and some cargo is lighter than others.

• #### Re: (Score:2)

Most of the early flights of the Dragon (including this CRS-3 flight) have been flying low value cargo to the ISS. Mainly food and consumables (spare parts, batteries, a few laptops, and other small stuff) that if it was lost wouldn't necessarily be all that important. As you've mentioned, this is also somewhat bulky, but there has been spare room left over. That is why one of the surprises that SpaceX sent up was some ice cream (a very rare treat in space) and a few bags of snack food that wasn't on th

• #### Re: (Score:2)

So NASA spent \$1.6 billion for the CRS program, that is for 12 missions [1] [wikipedia.org]. That is \$75 million for mission.

No, that is \$133 million per mission.

\$75 million is correct for \$1.2 billion for 16 missions.

• #### Re: (Score:2)

Well, you can simply use Google to figure out things. However, I was curious, so I did some of this leg work. The Soyuz-ST rocket that launches 7.8 tonnes to LEO [wikipedia.org] costs \$61M in 2006. That was just the launch vehicle. [google.com]
Now, that was just the launch, and that was almost 10 years ago. So, the price is at least 50% more (russian money has appreciated).
In addition, that does not include the costs of the progress itself. That is likely going to double the price. IOW, you are probably looking at 180M or so for
• #### Spikey (Score:1)

> "from its Harmony node"

Man, Buffy the Vampire Slayer has some powerful fans.

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