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Comment Curious (Score 1) 97

Per Wikipedia, the Soyuz-FG has a height of 49.5m, and the Soyuz-2 has a height of 46.1m, with identical widths. Now, it's possible that the Soyuz-FG figure includes the payload while the Soyuz-2 figure does not, but it's also possible this article is wrong (either it's something specific sized that "rocket is too small" can be a problem, or it's complete bullshit).

I'm actually not sure who would be more likely to be wrong, given a choice between Wikipedia and a Russian news source. Both have a pretty good history of inaccuracy.

Comment Too complicated to answer (Score 2) 90

Originally, there was CPU registers, and memory. Then there was registers, memory, and disk. Then there was registers, SRAM cache, memory, and disk. Then there was registers, L1 cache (on CPU), L2 cache (on mobo), DRAM, and disk. Then the L2 moved onto the CPU. Then there was L3. Then SSDs were added between RAM and disk. Now some chips have an L4 cache on the CPU package (but not the CPU die).

Oh, and there's a difference between latency and bandwidth. DRAM latency has not significantly improved over time, particularly compared to DRAM bandwidth.

And with multiple cores, some levels are core-specific while others are not. You can even have a bizarre situation where L1 cache is per-core, L2 cache is shared between two cores, and L3 cache is per-CPU (in SMP setups, that means main RAM is the first level shared among all cores).

Comment Two points (Score 4, Interesting) 194

First, while Mars requires a longer journey, it actually isn't substantially harder to send a rocket to than the Moon. If you use aerobraking, it's about the same delta-v. Yes, more consumables would be needed because the flight is months instead of days, which does affect the mass of the payload, but it may also be easier to build a sustainable colony on Mars (presence of an atmosphere and maybe water, higher gravity). So I don't think Luna is even really useful as a practice run.

Second, a launch schedule like this is pretty much the only thing I've heard that could justify the development of SLS. The entire project has smelled like "big bucks on development, goes over budget or budget gets slashed so it only gets used a few times" from the beginning. If they can get Congress to give them the budget for this, yes, that would be worth making SLS for. Will Congress spring for thirty-plus Saturn V-class rockets, for only three missions? I don't think so, but I hope they will anyway.

Comment Re:How to handle (Score 2) 361

Since this is something that seems like it would be difficult to defuse or even work on, what would be the best way to handle the situation where it's found in a location like this? The linked article indicates that attempts to diffuse the bomb failed and it left a five-story crater in the building where it was located, which is probably less than ideal.

Step one: Protect people. Evacuate the entire blast radius. This was done.

Step two: Protect property. If the bomb can be moved, move it to a remote area and detonate it. A bomb is not 100% inert until it has exploded, because until then it has chemical potential energy. This was not possible.

If the bomb cannot be safely moved, attempt to render it safe to move. This was not possible.

If the bomb cannot be rendered safe to move, attempt to disrupt its mechanism. They attempted to do so with an explosive charge, but were thwarted by a trap they had no knowledge of or way to discover. Today it's often done with an anti-materiel sniper rifle, but in this case that would probably not be used. The only tool I can think of that *might* work is a high-pressure water cutter, but even that might not have worked.

Comment Re:Hang 'em high... (Score 4, Interesting) 471

18 USC section 1031 would apply if Volkswagen obtained any EPA credits or other direct gain as a result of this testing.

I skimmed through the Federal Test Procedures, and didn't find an explicit rule saying "car should be in normal operating mode", however, I did not search exhaustively, and this is a SECRET mode. It isn't a turbo switch you push, it's picking up on the exact sequence of RPMs performed during FTP. It definitely violated the intent of the EPA regulations, which were explicitly stated to be "accurately simulating real-world conditions". There is no reason for this to exist except to sell cars that violate EPA regulations, and I don't think "you didn't write a law specifically against it" should stop them from getting fined.

Comment Laughable journalism (Score 4, Interesting) 221

"What’s more, liquid hydrogen fuel is not highly combustible mid-flight. Although hydrogen can be ignited, the risks of an explosion or fire are lower compared to conventional airline kerosene fuel"

Gaseous hydrogen is already a ridiculous explosive risk. Liquifying it only makes the resulting explosions bigger. They somehow think this is safer than Jet-A, which is actually less flammable than gasoline.

There are valid engineering reasons for the use of liquid hydrogen as a fuel, such as specific impulse or heat capacity. But safety is absolutely not one of them.

In other news, this is a blatantly obvious attempt to get funding for SSTO spacecraft development by disguising it as a less outlandish business plan. Seriously, this has much more in common with Skylon or VentureStar than with Concorde, right down to the choice of fuel. I wouldn't be surprised if many of the engineers are the same.

Comment Can they also add this option? (Score 1) 363

"Minimize turns".

On a recent trip, I knew that I could get there by going down to a major road, follow that to the start of another major road, then ride down that for about half an hour to get directly to my destination. However, I didn't know exactly where that destination would be, and I have a tendency to overshoot places, so I let Google drive me there. Even after removing toll roads from the equation, it led me down a completely separate path that involved all kinds of turns and twists. All told, took just as long as the route I would have taken, but was much, much more stressful because it was such a complex route.

Comment Re:Nice defense of Musk but wrong... (Score 1) 316

A railgun LITERALLY cannot put something into orbit. It can do suborbital trajectories, and it can theoretically do escape trajectories, but orbits are impossible. You end up with an apogee of however high, and a perigee of SEA LEVEL. Bare minimum, you need a rocket to raise your perigee above the atmosphere. And since the ram pressure during launch would be so tremendous, in practice I doubt a railgun can be built that breaches the Karman line with a worthwhile load.

Skylon is a very, very high-risk proposal. An air-breathing rocket needs to maximize the amount of time it spends in the atmosphere, thus it follows a much more depressed trajectory, thus reaching far, far higher speeds while still in the atmosphere, and the end result is that the thermal load placed on the craft is tremendous. And because Skylon burns LH2, it's an extremely bulky vessel as well, which exacerbates the problem.

SpaceX is following a calculated path. The first-gen rocket was tiny, and completely conventional. The second-gen rocket used a conventional layout, conventional fuel, conventional combustion cycle, but it did everything extremely well. It has the highest thrust-to-weight ratio of any rocket, and the highest specific impulse of any gas-generator LOX+RP1 rocket. They've been slowly pushing towards first-stage reusability, which gets you 90% of the benefits of SSTO, with none of the drawbacks. Their planned third-gen rocket is absolutely massive, uses a cutting-edge combustion cycle, and burns an innovative fuel. They aren't instantly revolutionizing the field, but they're on track to do it.

Comment Re:The event speaks for itself (Score 2) 316

What alternatives are there?

Railguns (or any other sort of ground-based propulsion) physically cannot put something into orbit, and practically speaking, they can only provide a moderate boost. You'd still need at least a full rocket stage, possibly two, to actually get to orbit.

Ground-based laser propulsion might work, but it's never been tested at scale. And if there is a catastrophic failure, it will be on the ground-based components, not the vessel. In other words, the big explosion will be on the ground instead of the air.

Air-breathing rockets are even more dangerous than traditional ones, since they spend more time in the atmosphere at extreme speeds and temperatures.

Electric rockets (ion engines of various types) don't have the thrust to break out of Earth's gravity.

Nuclear thermal rockets might work, but they won't be much safer IMO.

The problem ultimately boils down to "it takes too much energy to get to space". You're going from at best 400-something m/s to Mach 20+. That takes a lot of energy, and so we have to use very energetic means to do so.

Comment Re:It's always Stage III (Score 2) 72

IIRC, Stage III failures are responsible for a very high percentage of launch failures.

Well, let's see what statistics has to say.

I ignored failures of the payload, non-propulsion systems, or any failures where I could not identify which stage failed. Failures of staging mechanisms were rounded up to the higher stage. Flights with missing stages were still counted. All variants of each rocket family were included - Soyuz includes R7 launches, Thor/Delta includes Japanese licensed derivatives.

Soyuz: 25 first-stage failures, 18 second-stage failures, 29 third-stage failures
Proton: 9 first-stage failures, 11 second-stage failures, 17 third-stage failures
Ariane: 4 first-stage failures, 0 second-stage failures, 4 third-stage failures
Thor/Delta: 5 booster failures, 22 first-stage failures, 16 second-stage failures, 11 third-stage failures

Soyuz and Thor racked up a lot of early failures of the first stage, which seems attributable to simple inexperience (each had one failure from failing to fill the fuel tanks before launch). Even compensating for that, it seems the first stage is a dangerous stage, prone to failure.

However, your statement seems to bear out - the third stage does seem disproportionately dangerous. Oddly, it often seems to be control of the third stage that fails, not always the rocket itself.

Comment Redesigned at some point, obviously (Score 4, Interesting) 72

The Proton rocket has gone through a number of redesigns over its long life. The latest version, the Proton-M, first flew in 2001, and they kept flying the Proton-K for many years (for reasons I actually don't know). They've only done 90 flights of the Proton-M, and half of them were in that post-2010 period of "repeated failures" (although they had about as many failures for pretty much all of the 2000s as well).

I would highly expect the faulty pump to have been redesigned with the Proton-M modifications, based simply on that analysis.

The trouble with a lot of self-made men is that they worship their creator.