Please create an account to participate in the Slashdot moderation system

 



Forgot your password?
typodupeerror
×

Comment SpaceX is Working on this (Score 1) 105

This is precisely what SpaceX is working on doing with the Dragon series spacecraft, a combination of drag and propulsive landing, no parachutes, depending on the nature of the atmosphere and local gravity

If the body has no atmosphere (i.e. the moon), it would do a purely propulsive retro-fire and landing.

On a body with a thick atmosphere (i. e. Earth), drag on the heat shield would do most of the deceleration, with a final propulsive touchdown.

Mars is a middle case, there is some atmosphere but not nearly enough to do the job. It basically has to do a propulsive descent, but the trick is the rocket is thrusting against the oncoming atmosphere, so the aerodynamics are very complicated. Recent attempts to soft land the first stage of the Falcon 9 rocket have produced some very useful experience in this flight regime.

Comment Re:FFS just keep the Warthog (Score 1) 279

Alas, the A10 suffers one irredeemable fault - its only function is to support the Army.

Not quite, but close. Combat rescue aka "Sandy ops" - keeping bad guys away from downed airmen to effect a rescue.

But if we're not fighting against an enemy with an air force or SAM capability, this likely isn't needed

Comment Re:Need a wrench (Score 1) 99

Cost to get the material for the 3D-printer is going to be the same.

True, but if you can recycle the materials, you actually get to reutilize materials over and over again vs. launching a new batch from the ground. Part breaks? Toss it in the hopper and print a new one.

Also note that, for very long term exploration, the use of local materials is also being studied. Think concrete on other planets, that sort of thing.

Comment Re:Big Ships == Big Maintenance (Score 1) 118

I can't imagine digging a hole and filling it back in would cost more than all of the engineering, permits, environmental concerns, etc of building a permanent coastal docking facility and the long term savings from not having to worry about mooring, storms, water levels & maintenance should be significant.

Not so, sadly. What you propose would cost upwards of 100s of millions of dollars, would probably be more of a permitting and environmental nightmare, and it isn't physically feasible in a lot of places (places where it is feasible already are dock yards, like Brooklyn NYC).

And then there is the experience of stepping onto a floating vessel, even at dock. It is a museum, and so a big part of the draw is the experience. It is an amazing thing to see the Massachusetts, a big hulking piece of steel, floating.

Comment Re:Need a wrench (Score 4, Insightful) 99

$10,000-$20,000, same as the first one. It currently costs about $10,000 per pound to get anything to low Earth orbit.. Doesn't matter if it is a wrench or a can of ham salad or toilet paper - $10,000 per lb. You have to put the thing on a pricey rocket to get it to orbit. If you go to Mars, things get even more expensive.

This work that they are doing on the "Irrelevant Space Stopgap" is the stuff that they need to figure out before we can get to Mars or beyond. We have to sort out parts and tools and make sure that the astronauts can get their hands on what they need to get the job done and go to these places. Yes, it's a lot of seemingly basic and mundane crap, but it needs to be done and it is being done on the ISS today. There isn't a Tractor Supply on Phobos (not to my knowledge, anyway).

Comment Re:WHY? (Score 4, Informative) 54

I'm not worried about some internet group getting into the systems remotely. A Stuxnet-type attack is definitely possible, but smart protocols (no unauthorized electronics, thumb drives, etc. on site) will make this very hard. Someone will eventually goof up, but even then there are so many overrides that executing a safe shutdown is possible even if the control systems are hacked.

I think a physical on-site attack is far more probable and worrisome (terrorists with guns taking control of a plant). There is a lot of security around U.S. plants these days, but a whole lot of complacency has built up since 9/11 and a few thousand days of nothing happening takes a toll. 20 well-armed jihadis ready to give their all for Allah and their 72 virgins could probably get into a plant. What they could do from there, who knows. Simply getting into a containment and draining a reactor pool would be pretty bad if there was a significant amount of fuel stored (which is the case in a lot of old plants) but containable. They would have to figure out how to shut down and/or disable a lot of safety controls to do anything serious. The plant itself would fight them pretty hard. If they got physical access to the containment and tried to blow up stuff, could be bad but likely containable. PWRs have systems to cope with large break loss-of-coolant accidents, which is pretty much a massive steam explosion and loss of core cooling, as bad as things get.

I honestly don't think terrorists could do anything that would cause anything worse than contained damage and contamination, nothing that would harm the neighbors. However, given the FUD already circulating about nuclear power (yeah, I'm looking at you Mr. Burne) I think it would be enough for them to just take the plant and then sit around drinking coffee. Even if they did no damage at all to the plant, got mowed down by the good guys in 10 minutes, the simple act would have the world shitting bricks. And that is what terrorism is all about, stirring up unaccountable fear.

Comment One Can Design for the Material (sometimes) (Score 1) 99

If you know you are limited to a certain material, in some instances you can modify the part design to do the intended job with that material. In some instances you absolutely need a certain surface hardness or thermal properties or whatever which prevents this. But you can redesign a wrench for requisite stiffness and strength, it just won't look like a steel wrench and might be too bulky and unwieldy to use in certain places.

Comment Re:WHY? (Score 4, Informative) 54

Most currently active reactors were designed, built and certified in the sixties and seventies. All systems in those plants are 60's or 70's electronics. Most won't even have something as modern as a pdp-8 to control stuff. Go watch the China Syndrome if you need a reminder.

Having worked in the field, I need to call bullshit on this. Umm, yeah, the China Syndrome was fiction . And yes, while many active reactors were designed, built, and initially certified (FTFW) in the 60's and 70's, they have all undertaken numerous upgrades and safety improvements since.

Hollywood and Reality are two different things (hard to tell in the U.S., but it's true!). Nuclear operators have to work very damned hard and jump through a lot of hoops to demonstrate that their plants are safe to operate. Dealing with FUD dispensed by people who think they know it all because they watched it in a movie is the reason nuclear power is so expensive relative to other alternatives. But you can spout your ignorance some more if you would like; it's a free country I'm told.

Comment Big Ships == Big Maintenance (Score 4, Informative) 118

These ships are not cheap to maintain, even in museum status. The battleship U.S.S. Massachusetts, berthed at Battleship Cove, costs over $1M per year to keep in presentable and safe condition for tourists, keep the lights and ventilation on, etc.., and that doesn't count the significant volunteer work that is done for free.The pier built for it was something over $10M IIRC. That's all for a ship that doesn't go anywhere anymore. It just sits and floats. I believe Battleship Cove was offered the U.S.S. JFK (Enterprise(?) class nuclear carrier), but they simply could not afford to build the proper pier structure for a ship of that size, never mind the annual upkeep.

Just sitting in the water takes a big toll on these vessels. They need hull maintenance and paint regularly. Their hulls wear thin over the years due to corrosion, and periodic corrosion removal and repainting. If you just left them to the weather and never maintained the hulls they'd probably rot through and sink in a few decades.

Slashdot Top Deals

Understanding is always the understanding of a smaller problem in relation to a bigger problem. -- P.D. Ouspensky

Working...