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Comment Re:Speaking of delays... (Score 1) 106

ULA's track record with the Atlas V: 100%

Yes, let's take one vehicle in its fifth generation (not counting subrevisions), and ignore its track record with all of its earlier versions that led up to this point and all of their failures, and all of Lockheed and Boeings' other launch vehicles over time, with all of their failures. Lets also ignore that they're going to have to switch engines soon, to an engine with zero track record.

Payloads typically launch on schedule or within a few weeks. .... Some payloads have been waiting literally years due to delays.

Let's totally ignore that Atlas V launches once per two months, while SpaceX launches once per month, and that almost all of the wait time was due to investigation backlog. When it comes to hitting launch windows, SpaceX has a higher average success rate than average than Atlas V

And lets entirely fail to mention the point that ULA charges nearly double what SpaceX does per kilogram. Or that SpaceX is doing everything while rapidly evolving its rocket, to the point that they've basically even switched propellants partway through (denisification radically changes their properties). And while at the same time running an aggressive recovery and refurbishment programme and developing a heavy lift vehicle, with a small fraction as much capital.

Comment Re:What governmen brought to the table (Score 1) 106

As if liquid boosters can't fail catastrophically? Check out SpaceX's last failure. Liquids are hardly immune to catastrophic failure.

And actually more to the point, you've got it backwards. The SRB failure on Challenger was slow, more like a blowtorch. The explosion was when it compromised the external tank (which, obviously, stored liquids).

Solid propellants aren't like explosives. More to the point, you have to keep them under pressure to get the sort of burn rate that is desired for a rocket.

Comment Re:Speaking of delays... (Score 2) 106

Could you remind me how many people SpaceX has killed? Boeing and Lockheed have certainly killed people in the past.

If you're referring to the AMOS 6 ground failure, ignoring that part of the whole point of flying a stack unmanned as much as you can before you fly it manned is to shake out any problems, is that a manned mission would have almost certainly survived that. Unless the launch escape system failed, despite the drama, that was an eminently survivable. How do we know this? Because AMOS-6's hypergolic propellant tanks didn't ignite until the satellite hit the ground. AMOS-6 had the fairing as some extra protection, but on the other hand, the satellite itself isn't nearly as durable as a crew dragon.

The launch escape system ignites within milliseconds of a failure being detected and almost immediately reaches full thrust, accelerating away at 10gs. Here's a graphic of Dragon's abort test superimposed over the AMOS-6 failure. Things like this are the very reason that launch escape systems exist. NASA's last manned space vehicle lacked such a system entirely. And while their design for the Shuttle ultimately wasn't chosen, you know what? Lockheed's proposal didn't have one either. And it had a strong impact on influencing the final Shuttle design outcome.

Comment Re:What governmen brought to the table (Score 1) 106

SpaceX and Blue Origin would not use solids, not because there's something wrong with solids per se, but because they're not "fuel and go", which makes them expensive to reuse - and SpaceX and Blue Origin are all about reuse.

A lack of experience with hydrolox surely factors into the picture for SpaceX and Blue Origin; they'd get significantly higher payload fractions by using a hydrolox upper stage. But they're willing to accept lower payloads in order to simplify their manufacture and ground infrastructure, and in particular because the need their propellants to be storable, and storing LH for long periods is a PITA. Storing methalox is quite difficult, but nothing compared to hydrolox.

Comment Re:What governmen brought to the table (Score 2) 106

Solids really aren't that bad when reusability isn't a concern. They're very high thrust, which is exactly what you want out of a booster, and they're structurally very simple. Their low impulse and high structural mass are not particularly important aspects for boosters. Reuse of solids however gains you very little, because there's so much work in refurbishing them.

Comment Re:What governmen brought to the table (Score 3, Informative) 106

That's not the reason you don't use it for a first stage. The disadvantages of hydrolox (which are numerous) are offset by its incredible specific impulse. But for a first stage, specific impulse doesn't matter that much, while thrust matters a lot. Thrust is in large part proportional to fuel density, as a turbopump sweeps out a fixed volume per rotation, so the denser the fuel, the more mass (and generally all else being equal, energy) it pumps per rotation.

Another aspect is that first stages are big, meaning that cost is more important than specific impulse. By contrast, when dealing with an upper stage, a small increase in mass has a huge increase in first stage size, and since first stages are so large and expensive, that's a big cost. So you generally want a higher ISP upper stage. With the caveat that "storability" requirements for engines that need to restart can shift the balance; because hydrogen is so deeply cryogenic it's difficult to store for protracted lengths of time. Also, the longer you plan to have a stage in usage without maintenance, the more you tend to favour simple propellants over high performing ones, particularly when you're dealing with small, light engines. So for example if you have an interplanetary probe you'll tend to favour a self-pressurizing hypergolic system so that you only have to rely on a couple valves working, even though self-pressurizing propellant tanks are heavier and hypergolics tend to be lower specific impulse. Engines that are smaller still are often monoprops for an even greater degree of simplicity.

Comment Too transient, how about redoing it as a poll? (Score 1) 85

I've been reading a lot of these books over the last few years and would even be glad to contribute a few comments, but... Too transient to justify the effort. How about redoing it as a poll? The current poll has been basically dead for a week or two, and this would seem to be a much more interesting topic.

You could get the top candidates at random, but I'd recommend using Amazon to get the bestselling examples for the top 4 or 5 slots and collect the others in the comments.

Seems to be a problem with the Cowboy Neal option. If it was about the creation of Slashdot, there's not much grounds for recommending it. Perhaps an option like "Cowboy Neal doesn't read books anymore"?

Comment Re:Opposite (Score 5, Interesting) 541

Exactly.

I'm a gen X'er and I *know* I won't have a pension. Even if I retire, the government or the pension providers will default on me - either through inflation, or just because the damn pension providers will flatly announce they just don't have anything left in their coffers. I know this because they've already done it to my dad, who was born in the silent generation. So it's nothing new, but it sure won't get no better.

So, I'm not putting any money in a system that'll shaft me and I'm not saving anything for old age - most likely I'll be working until I die anyway.

What I do instead is, I enjoy as much free time now while I'm still young: I found me one of the last "old-style" jobs still available that lets me work 36 hrs/week with unreasonably great pay, in a heavily unionized old company that does business in a market that doesn't know the word recession.

In other words, I've maximized my salary/work ratio and I do as little work as possible to enjoy life the the fullest while I'm still in a condition to enjoy it. Time enough when I'm old and decrepit to kill myself at work for a living.

Comment Re:Wonder how it compares to Airlander (Score 1) 119

That accident sure was a black eye for them... but the design is now better because of it. Also, gotta love having an aircraft whose crashes are in slow motion ;) "Coming soon on World's Least Dramatic Air Crashes!"

I imagine for the pilot it was sort of like when you're driving down a slope on ice and you lose traction, and you end up skidding down the whole slope at a several kilometers per hour: First, alarm and futile attempts to regain control, followed by acceptance, then "Okay, you can stop any time now...."

Comment Re:Going Howard Hughes... (Score 2, Informative) 119

Airships are not party balloons; they don't "pop" when you make a hole in them. They have low overpressure and a huge volume to surface area, so a "bullethole" is just a slow leak; it's not even a reason to land. A helicopter is far more vulnerable to small arms fire than a helium airship.

As for what it buys over a helicopter, show me a helicopter that can move 50-500 tonnes payload at a per-kilogram rate cheaper than a freight truck while flying halfway around the world without refueling. Because that's what people are looking to build with this new generation of airships. Even Airlander 10, which is just a commercial prototype for the Airlander 50, carries more payload than the largest helicopter used by the US military, the Sikorsky CH-53E Super Stallion.

Comment Re:Going Howard Hughes... (Score 2, Interesting) 119

A common usecase for large airships is remote mining operations. They need big, heavy pieces of equipment brought into places without roads. Currently, the first step is to build a road - which is expensive and environmentally destructive. An airship needs only a clearing - and the "skycrane" variants don't even need that.

Another advantage is that it's much easier to design them to carry "bulky" cargoes than airplanes. Again, especially "skycrane" designs where the cargo hangs beneath.

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