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Comment Re: Note that what's large... (Score 4, Informative) 76

Venus has multiple "tropopauses" and "stratospheres", depending on how you define them. The atmosphere is like a layer cake with multiple convection zones (like Earth's troposphere) separated by areas of dynamic stability (like Earth's stratosphere). And again, ~50-70km is an awfullly long way from the surface, and surface winds are weak. But, there's a lot about Venus that we don't understand.

Comment Note that what's large... (Score 3, Informative) 76

.... is the size, not the intensity. The air moves only slightly faster or slower than the surrounding atmosphere as one passes through the wave.

They weren't expected on Venus, though. Venus's surface is dozens of kilometers down, thick and "soupy" there, transitioning to thinner layers above. It was surprising to see that surface features that far away, in a fluid that can compress, would still make clear phenomena like gravity waves in the high atmosphere.

Comment Am I the only one... (Score 5, Interesting) 129

.... who can't help but cheer at my screen when they nail one of those landings? Now I finally understand how sports fans feel when they watch a game and do the same thing ;)

One thing nobody can deny about them is optimism. ;) Seriously, their IPS numbers are, pardon the pun, out of this world. $200k per booster launch. $500k per tanker launch. I mean, really? Good luck with that. No, seriously, good luck with that; I won't be expecting anything close to that, but please by all means prove me wrong ;) ITS would be a great system to have, I've been playing around with some Venus trajectories with it recently. Looks like it can do a low-energy transit with nearly 300 tonnes of payload from LEO and back again with the same, over 400 if starting at a high orbit - but from an economics perspective the high energy transfers actually make more sense.

I noticed a lot of people were confused about why Musk wanted the trips to be so short and was willing to sacrifice so much payload to do so - many assumed it had to do with radiation or something. But the issue is, when your craft costs so much but your launch costs are cheap, you can't have it spending all of its time drifting in deep space, you need to get it back for a new mission as soon as possible. There's a balancing point, in that if you try to go too fast, you reduce useful payload below the point of making up for it with going faster - but a minimum energy trajectory is just not optimal when the ratio between launch costs and transit vehicle cost is so extreme. I come up with the same thing from Venus as they were getting for Mars, although for the Venus case you end up aerobraking to a highly elliptical orbit rather than to the surface for ISRU refill (you need ISRU, but for the ascent stages, so it's not realistic to do so for the return stage in the nearer term). So for Venus they get no refill like on Mars, but they also don't have to do a powered landing nor do an ascent on return - it's six of one, half a dozen of the other. Both are quite accessible with it.

Comment Re:Great strides (Score 1) 129

It depends what you mean by "refurbishing"; each element is different.

The solid rocket boosters, for example, suffered a hard impact into salt water. They then had to be fished out of the water. And of course you don't just "refill" a SRB, they have to be taken apart and recast, then put back together.

The ET is disposable, and had to be rebuilt from scratch.

The orbiter was legitimately reusable, but with design flaws.

I don't blame the shuttle program - they were sort of pigeonholed into this dead end by circumstances. The concept came about during the heyday of the Apollo Programme, when NASA budgets were serious. It was supposed to be a much more reusable, much more maintainable, and somewhat smaller system. It was supposed to then have a huge flight rate supporting all of these big projects that were on NASA's docket, including a permanent moon base and a huge manned orbital station dwarfing ISS, which was supposed to replace Skylab.

But of course, Vietnam and the realities of having soundly trounced the USSR in the space race led to their budgets being slashed, which pushed the program into ever more untenable positions until it was nothing more than a jobs programme. Forget full flyback reusability of all parts. Forget the titanium frame for the shuttle, which would have let it run hot and thus not required so sensitive of a TPS. Go begging for money and be forced to modify the design to meet Air Force requirements, pushing you into an inferior design position. On and on.

If I'd fault them for anything, it'd be for going straight for a full reusable workhorse rather than a small-scale pilot programme first. But those were the days of optimism. Optimism which only recently seems to start being regained.

Either way, the Falcon boosters are a very different beast. A vertical soft landing is hugely different from the SRBs, yet the thermal issues are far easier than with the Shuttle. And the Merlins were designed from the start under the principle of preventing the need for a full teardown. That doesn't mean that they will be cheap to reuse. But it does mean that they have the possibility of it.

I do think SpaceX had a rather clever strategy, in that while their goal was reusable, they made a rocket that in the process was cheap as a disposable. So they could get volume and flight history while working on getting the kinks out. They may have flown too close to the sun with the densified propellants and (externally) unlined COPVs, but obviously, with a company like this, their whole existence is to push the envelope.

Comment Re: Awesome (Score 3, Insightful) 129

Most of Europe agrees with you. And even the US agrees with you up through high school plus with various forms of assistance for college, including state-subsidies, particularly for state colleges, and federal subsidies (direct subsidies, tax credits, and tax breaks), roughly $80B/year each. Pell grants alone cost the government $35B.

Comment Re:No Gut no Glory (Score 1) 67

To be clear:

  * Getting the failure rate down in the lower tenths of a percent or better is what they need to be able to ~10x their launch rate and still be economically viable, since a pad explosion will leave them stuck for just as long and scare off just as high a percentage of their customers whether they're launching 12 a year or 120.
  * SpaceX wants to have reliability like airplanes, and has talked about this frequently.
  * What they want to achieve, and what they need to achieve, are not the same thing. They do not need to achieve airplane-like reliability for the Falcon 9 to be viable.
  * That said, if they ever want to achieve their ultimate IPT plans, they absolutely will need airplane-like reliability. Because they're calling for ~1000 launches per booster on that thing with a turnaround cost of ~200k. They really cannot have anything go wrong with it.

Comment Re:No Gut no Glory (Score 1) 67

It most certainly would be extreme reliability by the standards of the launch industry. The only ones that have better reliability than that that don't have nearly a statistically significant enough number of launches under their belt to assert that. Aka, "they haven't had a failure yet but nowhere near the several hundred launches required to assert a lower fraction of a percent or better failure rate".

We're not talking about airplane reliability here, we're talking about economics (the title of the article is "SpaceX Accident Cost it Hundreds of Millions"). Airplane-like reliability is for the future. We're living in the present.

All COPVs use an inner liner. The problem with SpaceX's COPVs is that they have no outer liner to separate the carbon fibre from the LOX. Outer liners are optional. SpaceX didn't use one. They lost a rocket because of it. They're going to keep trying doing without one. I really hope it doesn't cost them another. CF and LOX aren't fast friends.

Comment Re:Permission? (Score 1) 62

It's hard enough to find affordable LOX dewars. Seems like little ones cost about as much as big SUV-sized tanks. Everyone has LN2 dewars for sale, but you don't put LOX in a LN2 dewar as a general rule unless you're absolutely positive it has no organics (and preferably no silicone) in it, or certain metals. Otherwise it can get a bit... "explodey". The simpler, all-stainless LN2 dewars usually don't have lids, which with LOX would be just plain stupid. You can find used LOX converters online for very cheap, but they generally only will take LOX in, you can only get GOX out.

What I'm saying is if anyone happens to run into an affordable LOX dewar, drop me a line.... ;)

Comment Re:No Gut no Glory (Score 2) 67

It's a somewhat problematic business model.

If they $250M per failure and have a failure 5% of the time on a $62M rocket then the per-rocket cost is $12,5M, or 20% of the rocket's value.

Now they're trying for two things: a big scaleup, and greater safety. So let's say that they get the accident rate down to 2%, and they 10x their value. The cost of a failure should scale proportionally to the size of their market because it means a standstill in launches, the same reputation hit, etc. So now it's a $2,5B failure, occurring 2% of the time, or $50M per launch on a $62M rocket, aka 81% of the rocket's value.

Their business model and scaleup plans appear to be built on a premise of extreme reliability. Whether they can ever actually get that, I don't know. I like to hope so; airplanes have done it, and I know they're thinking, "if we launch enough, like them, we'll have gotten all of the potential kinks out". And there's probably some truth to that. But can they scale reliability at the rate they want to scale their launch rate? I have my doubts, and if so, their expansion plans (and thus business model in general) is erroneous.

A particular aspect that concerns me about them getting failure rates down into the lower tenths of a percent is their use of unlined COPVs. I don't trust them. I don't have some massive level of confidence that simply toying around with their pressurization regimen and getting better at void prevention is going to provide some sort of permanent fix; LOX and composites just plain don't play nice together. Their solution is like (to be hyperbolic here) having a nitroglycerine-fuelled rocket and losing one because during pressurization the tank buckled, and the buckling set off the nitroglycerine, and then announcing that you've got a solution and the tank shouldn't buckle anymore. Well, that's great, return to flight and all, but at the end of the day, you still have a nitroglycerine-fuelled rocket.

I'd feel a lot more comfortable about their business model if they announced plans to switch to lined COPVs, and take the (several dozen?) kilogram mass penalty. But as I always say, I would love to be proven wrong on this!

Comment Re:Threshold (Score 1) 404

Trade school can be a good thing. There are a lot of people who are plenty capable and interested that can for whatever reason not manage to learn to learn on their own. They simply need to be lead. There is an even larger number of people who are interested in something but simply could not invest in the technology and equipment need to learn on their own. Trade schools are a good match for both groups and there is a lot of overlap between both groups as well.

I am not saying there isn't value in a liberal arts degree and that some people don't need them to do what they do. Most people can't put food on the table using their ability to critique of renaissance art however or with their knowledge of western history.

What everyone really does need is a solid foundation in reading, physical science, and basic maths (like up thru calculus), a solid grasp of chemistry and physics won't hurt but might be more disposable. We *should* be getting these things from our secondary education system. The trouble is many people are not, and rather than addressing the question why can leave high school without being able to apply algebra, they want to teach everyone python! That is a problem. Its been a problem too for decades now colleges have been simply reducing their exceptions for freshmen and adding remedial classes to compensate. The real reason nobody can get a job without a college degree now is: I really don't know that you have the skills to make a proper cup of coffee if you have only a high school diploma.

Comment Snowden (Score 4, Insightful) 311

Manning and Snowden are simply not comparable at all.

Snowden for his one personal beliefs about the legality and morality of the situation acted. Yes he did violate the law but that was after he attempted to use the proper channels and was shut down. When he finally did go to the press/public he made arrangements to filter, redact, and limit the release of the material with the help of a few trusted press agents. It was of course necessary to disclose some secrets because without doing so the public/press would have little to no way to affirm the credibility of anything he was saying about the existence of the invasive domestic spying programs.

Manning was entirely different. He basically was talked into doing what he did, and had help of an external actor. His reasons appear to be more born out of a desire to personally get even with 'the system' than to be a reformer. He made no effort to use the proper channels that we know of and little effort to control the release of material. He certainly took no personal responsibility for material handing it all to wikileaks with no judgement of his own about what was or was not to harmful to leak.

Finally Snowden's leaks might have harmed intelligence gathering efforts, disclosing methods and capabilities but they did not out people as Manning's leaks almost certainly did. There is cause to believe lives may have been lost due to Manning's leaks. That issue alone should make it a very different discussion about pardoning him, and the moral justification for his actions.

I can see a pardon or reduced sentence for Snowden but there is no way I would ever let Manning out of the clink.

Comment Re:Pardon Manning and Snowden (Score 2, Insightful) 311

No you are by referring to her as Chelsea. Manning has a number of serious mental illnesses and you are not helping him by enabling his delusions or lending credibility to the charlatans currently in charge of his care.

Rather than helping him get healthy so he can one day go on to have a family if he so chooses you are allowing him to do irrevocable harm to his body, that is sure to leave him sterile and shorten his own life. People like you are terrible human beings. Your willingness to prey upon sick to advance your political agenda makes you the worst kind of monster in my book.

Comment Re:Now this is just getting stupid (Score 1) 562

I had ones that could do that but it was very slow and you certainly could not just say "play track 5". I have a turn table with a laser that shines on the disk and a photo sensor that can detect the level of reflected light. Its able to find tracks about 90% of the time. It moves the tone arm to the edge of the disk, and scans across counting the blanks spaces, its pretty fast. Once it counts the right number of spaces it drops the tone arm.

Its not CD player fast by any means but its way fast than seek on any consumer tape desk has ever worked.

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