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Comment Re:Destructive test does not mean 'blow it up'. (Score 1) 373

OK, I see - the person you replied to mis-used the term 'destructive testing' to mean repeatedly launching the rocket until it destroys itself. Yeah, that would not be competent, and would tell them nothing.

Real destructive testing is used all the time. SpaceX themselves would destructively test a sample of every part they buy, or build. Parts of this rocket will be destructively tested to confirm what their models tell them. But you knew that.

Comment It is CRS-4, which soft-landed in the ocean. (Score 3, Informative) 20

The mission this piece came off was CRS-4. This mission was one of the first missions where recovery experiments were done.

After separating from the second stage and payload, this first stage was spun around, the engines re-lit to slow the rocket down and allow it to re-enter the atmosphere on one piece. It then fell through the atmosphere, before the engines re-lit a third time to slow it down, and it splashed down at slow speed. At this point, the stage would have fallen over, and the pressurized tanks would have burst.

A good run down of the landing attempts are on a page in the reddit spacex wiki at www.reddit.com/r/spacex/wiki/dev

They identified that this was from this stage by eliminating all others.

It wasn't from the rocket that exploded, because that rocket had grid fins added, and the location where these fins would have been is on this piece of debris. In addition, not enough time has passed for debris from that event to have reached the Isles of Scilly. This also rules out any recent launch, for the same two reasons. It would also be assumed that the destruction of CRS-7 would have caused more damage to this piece than we see.

Of the other launches, they ruled out early ones because the designs of the flag and logo didn't match, and that they would have been destroyed by reentry as you said. That left about 5.

They then compared images of the rockets on the launch pad with the images of this debris. The locations of items (lumps and bumps, basically) on the interstage only matched for one launcher: the launcher for CRS-4.

Once this was confirmed, it matched with a serial number located on the stage. Earlier this year, a piece of the fairing from another launch was found washed up in the Caribbean. It had a similar serial number on it. SpaceX quickly confirmed what launch it was from, and it was noted that the 'core number', that is, sort of the serial number for the whole rocket, was embedded in a particular place in that part's serial number. In the same place in this piece's serial number was the correct core number for CRS-4. So they had their answer. All we are waiting for is SpaceX's confirmation, which should come in the next few days.

Comment Re:Data data everywhere and not a drop to think (Score 1) 366

Oh, don't forget - 5. 'won't break'. And 6. 'Doesn't weigh too much'.

A load cell (or strain gauge) is a device that flexes depending on how much force is on it. They want to put this between the wheels and the suspension, and leave it there to take the impact forces of landing. It would only be a matter of time before one of these would develop metal fatigue, snaps during a heavy landing, and kill a plane-load of passengers.

Comment Re:It's always Stage III (Score 4, Interesting) 72

That is really not that surprising. All the design constraints in rocketry really come to a head in the last stages. Every kilogram of mass in your last stage is a kilogram less payload you can carry, and it is where you really need the most efficiency, the peak isp, so you want to push the pressures and temperatures as high as you can.

As light as you can make it, as powerful as you can make it. This leads to fine tolerances and making the design only as strong as it needs to be.

Comment Re:Assuming you are not just trolling..... (Score 2) 150

Anything small that is (cosmically) near something big is in an orbit of that big object. Read that again. Then read on.

From here on, I will call the two things 'rock' and 'sun'.

We still call things going very fast as being in an orbit. We call these hyperbolic orbits, and this orbit carries the rock away from the sun after a single pass. These items have 'escape velocity'

Anything at less than escape velocity will be in a normal orbit. A normal orbit is not circular, it is an even, oval shape called an ellipse. The earth's orbit is nearly circular. We say that the earth's orbit has 'low eccentricity'. Its speed doesn't slow down or speed up much over its orbit. It stays at around 30 km/sec all year. A comet's orbit is highly eccentric. When it is far away from the sun, it moves very slowly. Then it falls toward the sun, gaining speed. But that little bit of movement it had caries it away from the sun, so it misses the sun. The sun's gravity pulls the comet around, flinging it back out where it came from. It slows down again as the sun's gravity pulls it back, until it slows down, turning, and falls back again.

So, let's examine your statement that "anything that approaches the orbit of any body in space , will be drawn in to that body by virtue of gravity, unless it has sufficient mass and momentum to maintain an orbit." There is something here that has created this understanding, the understanding that anything that is moving will be stopped by friction. Any movement soon stops. But what is there is space to make a rock stop moving? There is no air to slow it down, no carpet to rub against. Only if it happens to run into something else, and there is not much in space to run into.

Anything that approaches a body in space will be in an orbit.

There is also the understanding that small things stop easier than big things. But this is again tainted by the fact that your life has been lived on a planet, with air things have to push through and surfaces things have to rub against. Forget those things - there is neither in space - and small things keep going just as well as big things. The little thing has less momentum, but it also has less weight - the force of gravity on it - and the two things cancel out. In all orbital equations - as long as the 'rock' is much smaller than the 'star' - the mass of the rock cancels out, and is irrelevant. For our original premise - which was the idea of launching a payload of nuclear waste into the sun, by the way - the payload of waste and the earth follow the same equations - their wildly different masses are irrelevant.

What about when you throw a stone at your brother? That stone is an object near the earth. Surely it isn't in an orbit? Well - it is. It follows an elliptical path like anything else. It is like that comet, moving fairly slowly far away from (the center of) the earth, and it would continue in an orbit unless something - your brother, a window, the earth itself - gets in the way. If you could throw it at 8 or 9 kilometers per second (and if there wasn't any pesky air) it would remain in orbit, travelling right around the earth to hit you in the back of the head 90 minutes later.

So, what would we have to do to get a payload off the earth, and to the sun? First we would have to get it away from the earth, and that is not easy. But once it is away from the earth, it would still be orbiting the Sun. We would need to slow it down, almost to a stop - from 30km/sec down to zero. That is hard. Remember, there is no friction out there, no tyres on a road. You have to use a rocket engine pushing backwards, and it is just as hard to slow down in space as it is to speed up. The measurement of a space craft's ability to change speed is an important number, and is measured in meters per second - we call it the 'delta-V' of a spacecraft. The entire Saturn-V moon rocket had a delta-V of about 18 kilometers per second - without a payload. So magic a complete Saturn-V rocket away from earth, and it could get a tiny payload about two thirds of the way there.

Of course, once you did stop the rock, you would not need to push it toward the Sun. It would just fall - like a stone - towards the sun, reaching a speed of hundreds of kilometres per second before burning up from its own velocity. The Sun's heat would be nothing to the rock's own energy.

By the way, that Messenger probe to Mercury is a good example of how hard it is to get something to go towards the sun. In order to reach and place itself in orbit around mercury, the spacecraft was send on a multi-year path that took it once past Earth, twice past Venus, and three times past Mercury.

Well, this was much longer than I thought it would be!

Comment Assuming you are not just trolling..... (Score 4, Informative) 150

It is very difficult to 'shoot something into the sun'. You first need to get it out of the Earth's gravity, and then you need to decelerate it by 20 km/sec.

This is, frankly, impossible. You might be able to put a small payload to the sun if you used a very big rocket, and did a Venus fly-by. This way you could dispose of a few kilograms at a cost of a few hundred billion dollars.

Comment Re:So True. 'License' is not the right answer. (Score 1) 369

I wouldn't say there is 'no' reason, just a weak one. Different pods could require different treatment - more or less time, liquid or temperature - information on these is also encoded into the 'DRM' information.

Of course, in reality there is no reason to use a special fluorescent ink for this - apart from a foolish attempt at obscuring it! Really, they didn't think that the first person to find that a generic pod didn't work wouldn't examine the genuine pod under different light sources to find out?

Comment So True. 'License' is not the right answer. (Score 1) 369

The right answer is to publish a document on your website, liberally licensed, that outlines exactly what you have to do to make a KC2 capsule, right down to the spectral properties and the recommended formulae of the ink. Then everyone will be able to produce completely compatible cartridges that make use of all the brewer's features.

Comment Simply to avoid confusion. (Score 2) 136

If they called it a 'day', they wouldn't have known if it was an Earth day or a Mars day. If they relied on calling them 'Mars Day' or 'Earth Day', soon someone would have forgotten to maintain the prefix.

So they coined a new word to use for a Martian Day, and stuck to it.

For other planets, I expect that the same term will be used. 'Day' for time on Earth, 'Sol' for time on the planet. That said, we don't have all that many things that would have usable 'Sols'. Mercury's days last for months, Venus' day last for longer than its year. Maybe probes on minor planets, which look like they have days around 8 hours long.

Comment Google is fixing the Updates problem, effectively. (Score 1) 434

Google is fixing the updates problem. While the best way to fix it would be to somehow get device makers to provide them (How? This is never addressed!), Google has moved to resolve this another way.

And that is moving more of the operation from Android to the Google Play services, and Google - sourced apps on the store. These are regularly updated, and updates are pushed out through the play store in the usual manner. This allows most security issues to be rectified or worked around.

Personally, I'd like a different solution - requiring source drivers for everything and unlockable boot loaders, so Google or someone else can provide updates even if the manufacturer defaults - but I'll live with what I have. (What I actually live with is an old Moto Defy running 4.4.4 from CyanogenMod.)

Comment Neither do I... (Score 4, Informative) 157

Golden ratios emerge wherever you have a relationship of T(n)=T(n-1) + T(n-2). Where the first two terms are 0 and 1, you have fibonacci numbers: but no matter what your starting numbers are, the ratio between T(n) and T(n-1) will approach phi (as demonstrated with 'brady numbers').

So it is not at all surprising that phi might crop up in seemingly strange places.

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