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Comment: Re:Is Slashdot now fucking Facebook? (Score 2) 181

by FatLittleMonkey (#48174983) Attached to: Favorite clickbait hook?

Nothing to do with ads, or Facebook. "Clickbait" refers to the teaser headlines for articles/posts. Same thing you see on the covers of women's magazines, or used by TV news to keep people watching, where the key information is deliberately hidden. On internet sites, it's often taken to a meme-worthy extreme, where even the basic topic is hidden.

It used to be "What Jen's recipe for a great body?", "The secret your doctor doesn't want you to know!" and "Coming up, a story no concerned parent can afford to miss!"

Now it's "This one weird trick will change your life!", "You'll never believe what this woman does!", "You won't be able to stop watching this video!".

It works because SQUIRREL

Comment: Re:Power Source (Score 1) 348

I wonder what the trade is like between acres of cooling vanes vs. acres of solar panels. I guess it would depend on the efficiency of both.

In space, in a vacuum, studies apparently have shown that solar wins for the inner solar system. (And that's solar panels winning just compared to the reactor mass. Adding the radiator issue makes them win further out.)

On Mars, solar probably wins in terms of pure power/mass ratio, but solar requires storage for night power (so nearly double the panel area, plus the mass of the battery system) and extra power for heating (which the reactor gives you for free.) And in winter, the numbers get worse.

Same for the moon, except near the poles. With 24hr (or close to it) sunlight, solar wins. Anywhere else, nukes rule.

Mars's atmosphere is thin, but the temperature is very cold... seems like there ought to be a way to take advantage of that.

I was being dismissive: in reality a small reactor suitable for a base wouldn't need much cooling on Mars; after all, we're not talking gigawatt scale plants. So a small set of radiators — sticking up vertically, angled perpendicular to the path of the summer sun — would be plenty. But even that may nor be necessary, you'd use the waste heat for heating the base itself, then the lower grade heat for a greenhouse. At that point, the surface area is probably great enough for the atmosphere to carry the heat away without any special radiators.

[That atmosphere on Mars is annoying. It's too thin to be useful, but thick enough to get in the way. So it can carry enough heat away to make solar heating barely enough to keep greenhouses warm during the day, and at night (and in winter) you'd need loads of extra heating. Mars makes it hard to put up a freakin' greenhouse. And people want to live there.]

Comment: Re:Power Source (Score 1) 348

OTOH, on Mars you've got an atmosphere,

Barely.

so this wouldn't be a problem anyway.

Even on Earth we have cooling towers.

But eventually large-scale power will be needed in the outer solar system. I suppose by then we'll have figured out fusion or something like that.

At the very least, we'll have a better idea what our real needs are. Right now we're like Christopher Columbus trying to design the NY subway system.

Comment: Re:Replace rockets with something reasonable. (Score 1) 348

The space shuttle was a 100+ ton space-plane launched on a Saturn V class launcher. Built without any real precursors, from 1970s technology. Every aspect of it pushed the technology beyond the state-of-the-art. No part of it was built to reduce operating costs. The original proposal sold to Nixon may have been to develop a low cost "space truck", but that was never part of the actual program development goals.

OTOH, Falcon 9 was intended solely to be cheap. And is already the cheapest launcher on the market as an expendable. Even partial reusability (first stage) is expected to lower launch costs significantly. Musk claims that launch operations costs are a small part of his launch costs, and even that will probably drop once his team controls their own site and range.

This gets back to moving away from the "standing army" model of spaceflight operations.

Comment: Re:Power Source (Score 2) 348

Very large radiators.

And the radiators must be protected behind a heavy shield, because the radiation degrades them too quickly. Most designs have the reactor, then a heavy shield, a long truss and then the rest of the ship. Running down the length of the truss, carefully shaped to remain in the shadow of the shield, you have huge radiators to dump the heat from the reactor. The truss, the radiators and the shield are all additional mass required for a nuclear propulsion on top of the reactor mass. Solar arrays require radiators too, but only a fraction of the size, see the ISS.

Comment: Re:Get real (Score 1) 348

that only puts a few hundred to at most a thousand-plus kg of payload on the moon per flight.

You're doing it wrong. With reusable launchers you want to split your payloads into cargo and fuel, launched separately. Most products have a U or J shaped reliability curve. Higher failure rate at the beginning, picking up manufacturing defects, then lower failure rate until end-of-life effects start to accumulate. Because fuel is cheap, you put that on the brand new, untested reusable launchers, and on the end-of-life launchers and fly them until they die. Because cargo is generally not cheap, you use the in-between launchers, at their peak reliability.

You put your cargo and TLI-engines into LEO on the most reliable launchers using the payload full capacity of your launcher, then you add fuel tanks and associated plumbing on the less reliable launchers, finally you launch bulk propellant on the lowest reliability launchers. Then you launch these large payloads from LEO. You lose some Oberth efficiencies, but you gain in using your launcher's maximum lifespan, and being able to launch larger individual payloads (in the 10-12 tonne range for F9, 50 tonne range for FH, and 250 tonne range for the Raptor-based MCT.)

Comment: Re:Power Source (Score 3, Interesting) 348

No form of currently-achievable propulsion yields a higher Isp than a fission fragment rocket

We're so far from FFR, we might as well talk about fusion drives, or Harold White's warp drive.

and a few other space options (such as a nuclear VASIMR-like mode)

My previous comments apply to NEP vs SEP. SEP has better power/mass ratios until you are somewhere near Jupiter, and realistically probably somewhere past Jupiter.

Comment: Re:Begin planning use of Lockheed's fusion power (Score 1) 348

... using NASA designs as the foundation.

I've never understood this argument. By definition, you are saying that everything that is available to these private players was already available to NASA and its primary contractors.

So why is that a justification for minimising the achievements of the new guys? "Yeah, we could have done that. We didn't, but we totally could have." No, no you couldn't. You had decades to do it, your whole job was to do it, you had billions in funding to do it, your primary contractors are orders of magnitude larger than the new players, and yet you didn't do it.

Worse. Even after the new guys did it, you still aren't doing it.

For example, Boeing is getting a multi-billion dollar USAF contract to develop a new large methane engine. They got the contract because of their "decades of experience". Aaaand... they are sub-contracting the actual work to Blue Origin, a dot-com billionaire's tiny little hobby-project which has spent the last decade actually building new rocket engines. But hey, it's the new guys who are leaching off the old players. Sure.

Comment: Re:Replace rockets with something reasonable. (Score 1) 348

Most things can be broken down into sub-100 tonne parts. The problem is not the launch, at least once we stop throwing away our rockets, it's the cost of on-orbit operations. That requires a change in how we work. Ending the standing armies on the ground to support every spanner-turn in space.

Comment: Re:Power Source (Score 2) 348

Trade studies have suggested that out to the main asteroid belt, aerospace grade solar panels have a higher power/mass ratio than nuclear systems. Only out near Jupiter does the equation shift (but even that is only counting the direct reactor mass. The added mass of shielding, trusses for distance, etc, is usually not included.) And every year, the cross-over distance shifts further out.

The exception is where sunlight is unavailable — Lunar night, Mars winter — where the length of darkness exceeds likely storage capacity. However, the most likely location for early development on the moon is the poles, where there are Peaks of Eternal Light. (How can you not capitalise that?) OTOH, for Mars, you are probably going to avoid the poles due to the severity of those winters, staying within 30 deg of the equator, avoiding that problem too.

So it'll be a fair while before we need nukes, better to focus available funding on something else.

Comment: Re:crashing oil tankers (Score 1) 216

by FatLittleMonkey (#48160411) Attached to: When will the first successful manned Mars mission happen?

Whatever you manage to throw at the Earth will burn in the atmosphere.

Solid metal will pass through virtually unchanged. Shaped for minimum-drag in hypersonic entry (unlike capsules, which are shaped for braking), it will, by coincidence, be virtually undetectable by radar or optical until it hits the atmosphere. (Unless they are watching activity at the launch site, of course. Which they would be, if they aren't stupid.)

No-one saw the 10,000 tonne, 20m diameter Chelyabinsk meteor, which produced a half-megaton detonation. It was a stony-type meteor, hence it didn't penetrate below 25km. A solid metal manufactured impactor could easily reach the ground; but the optimum shape for a city killer would detonate in the air above the target, but below 5km.

If we see it coming we'll nuke you, even with barely modified 1950s tech.

To reach the moon with even a small nuclear warhead, you would need a full multi-stage rocket launch, not a little ICBM squirted out of a sub or silo. You couldn't hide such a launch. And it would be trackable for the entire 3 day transit to the moon. The lunar loony would just need to launch a load of gravel back along the same trajectory. No more warhead. He then throws some impactors at the launching nation's small number of suitable launch sites. No more counter-attacks. He can also hit a few LEO satellites to start a Kessler cascade, preventing any launches from Earth for several decades. His own impactors (being purely bulk-kinetic) aren't affected as they pass through.

The moon has "air superiority" over Earth due to orbital mechanics. It takes a lot more energy to bomb the moon than it does to bomb Earth. Therefore attacks from Earth must be much larger, and require substantially more infrastructure to launch, which is vulnerable to attack from moon-thrown spears-of-death. (The moon's disadvantage is that it takes a lot of infrastructure to get to that point.)

Mirrors should reflect a little before throwing back images. -- Jean Cocteau

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