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Comment Re:Fixed it for you. (Score 1, Funny) 402

When a woman gets married and has children, her whole life changes. Her husband is no longer the focus of her life, her children are. She loses interest in sex, and doesn't see why she should have to do it any more. If she wants another child, sure, but otherwise not. To her, it's just one more person who wants something from her at the end of a long day at work, and this one she can actually say "no" to. So, she does.

Meanwhile, the husband, cut completely off from one source of sex he is allowed to have, grows increasingly desperate and unhappy.

Okay, sorry for the tangent, but: how on Earth are people from the year 1958 managing to make posts on Slashdot that show up today? How are they even getting a bloody net connection back then?

Comment Re:So... (Score 1) 164

Child molesters: If someone calls in a report of a known child molester or a person acting suspiciously, you need police out there to investigate, not a drone zapping people from the air. If someone is running away with a kidnapped child, my "car chase, fast response" example above applies. Now, if you're talking about trying to keep drones in the sky 24-7 tracking the movements of all known child molesters, that's something that should be mandated by a court, not police officers just going off and doing. That's as intrusive as a court-ordered ankle tracking bracelet, and should be treated with no less seriousness.

Drunk drivers attacking police officers: I can't even envision how your mind is factoring drones into this situation. Are you proposing that drones make traffic stops instead of police officers?

Or maybe I'm misreading your post. Was that sarcasm? I can't even tell anymore.

Comment So... (Score 4, Interesting) 164

... So we're talking about poorly regulated government officials using flying robots to spy on and electro-paralyze people from the air.

How exactly is this not a dystopian sci-fi novel come to life?

Don't get me wrong, I think civil use of drones can be a great thing. Even police use of drones - tracking vehicles during a car chase, fast response to a breakin or robbery, etc. But this is just ridiculous.

Comment Re:Use RTGs for ion propulsion then comm. (Score 1) 77

First off, you say "dust lodged in the lungs" as if that's a good thing. It's an intensive alpha emitter. Check out how miniscule of quantities of radon (another alpha emitter) it takes to pose a health threat. But yes, most plutonium dioxide ingested in that form passes through (not without irradiating the digestive tract first, of course); the ingestion route is more hazardous for more soluble forms of plutonium.

Comment Re:And the timeframe for getting another probe (Score 1) 77

Venus has an incredibly hospitable environment... in the cloudtops. Vastly more hospitable than the surface of Mars. And with how little we know about Venus, even something that doesn't land could completely revolutionize our understanding of the planet.

A higher budget mission could use a ballooning lander that makes repeated descents to the surface, then rises to recharge its batteries and let its coolant chill back down. Wherein it would be far more of a "rover" than anything we have ever sent to Mars - it could explore the whole planet.

Comment Re:And the timeframe for getting another probe (Score 1) 77

Excuse me, I shouldn't have laughed. Ahem. Mercury has the highest delta-v requirement amongst the planets.

Which would have been a great response, had I written:

Venus and Mercury have the lowest delta-V requirements

Which is, of course, NOT what I wrote. What I actually wrote was:

Venus and Mercury have more frequent launch windows.

Moving on...

With Mercury you can't save energy by aerocapture, but you can make very frequent flybys of Venus and Mercury to lose velocity - and making observations of both Venus and Mercury during each flyby. Messenger, for example, was launched in August 2004. It did an Earth flyby 1 year later, a Venus flyby 12 months later, then a Mercury flyby 15 months later, then 3 years later, orbital insertion. Now, that was a long time to orbital insertion, but not a long time before the collection of first data - it did minor data collection at Earth, more at Venus, and more during its first Mercury flyby. But more to the point, it was done with a tiny delta-V budget: 316m/s from Earth escape to Mercury insertion and 862m/s for the orbital insertion itself. Mars takes about 390 m/s from Earth escape to Mars transfer, 670 m/s for Mars transfer to Mars capture (if you can't aerocapture), and entering a similar orbit on Mars would take somewhere in the ballpark of 2000 m/s (5000 m/s to low orbit) (again, possibly reduced if you can aerobrake). While it's technically possible to use an Earth gravity assist to Mars, it takes much longer.

Now, of course, one could have used a more Mars-like delta-V to get to Mercury much faster, although due to the complexities of gravitational assists I can't work out readily here just how long it would take. But for Venus it's easy: 280 m/s from Earth to Venus transfer and then... well, aerocapture is pretty much a given if you want to (far easier than on Mars), but if you don't want to do it, then it's another 360 m/s to high orbit, then 2900 m/s to low orbit. But of course, Venus is a very easy body to aerocapture at, so it should be expected. Short transfer times to Venus, little energy to get there, easy to brake at, and frequent launch windows. How is that not more "probe-able"?

Comment Re:Use RTGs for ion propulsion then comm. (Score 1) 77

1) There's nothing to make staging any harder for ion craft than for chemically-fuelled craft

2) Dawn's ISP has a max of 3100sec. There's plenty of room to be improved.

3) A probe at a gas giant (or moon with an atmosphere, such as Titan) could potentially orbit through the exosphere, scooping up new propellant. While that would be no insignificant engineering work, there's nothing making it impossible. The relative velocity of the ions it'd be scooping are far lower than the exhaust velocity of a good ion engine, meaning that it could compensate for the drag by thrusting with only a small fraction of the propellant that it collects. And most ion engines are very propellant-choice flexible - they don't have to use xenon, and it's not a huge penalty to use other gases. So such a probe could leave orbit and even return to Earth. As a bonus, any leftover propellant upon arriving at Earth would be a sample return.

My personal dream mission is something akin to #3 for Titan, with a VTOL rotary-nacelle lander carried along for the ride - the orbiter being its "tugboat" and communications relay. A one-year mission at Titan with realistic flight speeds and recharge times should allow such a lander to go to pretty much everywhere interesting on the moon. If the probe's payload was sufficient, the VTOL lander could be supplemented by an ascent stage (my calculations show that something like a scaled down Pegasus upper stage should be sufficient, and its propellant mix appears to tolerate cryogenic conditions), so you'd get small surface samples from all over Titan returned as well. And if you have a probe in the Saturnian system with an atmospheric scoop, you might as well do a Stardust-style aerogel flyby of Enceladus and scoop a bit of Saturn's exosphere on the way back - the mass penalty required for adding both to the mission is trivial. An Enceladus flyby needs a sheet of carbon aerogel with a closable shield (if desired, the impact velocity could be kept low if desired by entering into a Molniya-style Enceladus orbit, having near zero velocity high over the plumes). A Saturn scoop needs a tiny additional tank and valve so that its sample doesn't get mixed in with the bulk gas taken from Titan.

Seriously, the potential scientific value of all of those sample returns would be almost unimaginable. We don't even know what tholins are as things stand, and yet they may have been the progenitor to life on Earth. And there's always the chance that signs of actual life, past or present, would be found in Titan or Enceladus samples.

There's of course a lot of engineering work (which means unknowns, which means risk) in such a mission. So it would be wonderful if they could retire part of those unknowns by testing out propellant scooping at Uranus or Neptune.

Comment Re:Use RTGs for ion propulsion then comm. (Score 3, Informative) 77

1) RTGs are not being "phased out". They're actually going to become more common in the coming years, now that 238Pu production has restarted.
2) Computer power consumption has dropped, not increased.
3) For outer planetary missions, there is literally no better solution to produce X number of watts, whatever number X may be (up until you get into the many-dozens-of-kilowatts range, where it probably pays to start developing an outright fission reactor)
4) Few people would consider 238Pu to have a "long half life". There are certainly things that it's long in comparison to, but as far as "long lived radioactive" products are considered, it's not even close to being considered one.
5) Plutonium is not "rejected by the human body", it's accumulated in the bones, and alpha radiation inside the body has 20 times the destructive power of beta and gamma per MeV (also, with beta decay, 2/3rds of the energy is usually lost as a muon antineutrino)

Note: Please don't misinterpret this, I'm pro-RTGs. I just wanted to correct the facts.

Comment Re:Use RTGs for ion propulsion then comm. (Score 3, Insightful) 77

Why all spacecraft don't utilize the extremely high energy/weight RTGs for deep space PROPULSION is beyond me

First off, even with the little we use today, we already have a serious shortage of it. At least funding has been reestablished to produce more. But production rates are going to be very slow and expensive, and this means that the fuel will continue to be expensive. Unfortunately, 238Pu needs to be thought of as a manufactured product, not a waste product. It's impractical to extract from nuclear waste - you have to first separate out neptunium (which isn't too common to begin with, which means lots of reprocessing, which is expensive), and then you have to bombard it with a lot of neutron flux for a long time (neutron flux being very valuable, as it's what you can use to make power (by bombarding a fissile target) or medical/ industrial isotopes). And you need a lot of plutonium to be useful for space probes (kilograms), not the sort of ng/ug/mg quantities usually used in medicine and industry.

The net result is that RTGs are almost always the best option from Saturn on out, usually the best option for Jupiter, sometimes the best option for Mars and the asteroid belt, and seldom for Earth on inwards.

Comment Re:Ehh (Score 4, Informative) 77

Flagship is a technical term. NASA missions are divided into categories: Discovery, New Frontiers, Explorer, and Flagship. Flagship are the most expensive, and most infrequently launched. Flagship missions cost over a billion dollars, usually $2-3B. Because they're so expensive and infrequently launched, one expects a huge scientific return out of them - for example, although Cassini-Huygens cost $3.26B, it's returned such a treasure trove of data and incredible discoveries about the Saturn system that I doubt anyone would say it's not worth it. Is Mars 2020 going to return anything that worthwhile? Not even close. The sort of scientific territory it's exploring is far too well tread already; it's exploring small details, not huge unanswered questions. The Uranus or Neptune probes may or may not prove to be worth their price tag, but at least they stand a better chance. I know a lot of people for example itching to find out more about Triton after Voyager's tease, which was conducted with 1970s tech.

Comment Re:And the timeframe for getting another probe (Score 3, Interesting) 77

Mars is not the "next most probe-able remote object". Venus and Mercury have more frequent launch windows. And more abundant solar power. Capture is much easier at Venus, although surface survival is more difficult.

There are far more significant unanswered questions about bodies other than Mars that need "theory testing". Mars is the most studied body in the solar system outside of the Earth and the moon. And ranking the moon higher than Mars is at this point starting to get questionable. There are massive unanswered questions about many other bodies in the solar system. The incremental benefit for Mars is very low. Example: Venus is Earth's evil twin - such a close match for us in diameter and mass, formed right next to us, and yet it's a greenhouse hellscape without a magnetic field. We really don't know why. How much more of a fundamental geology question can you get than that? And as for fundamental biology questions, Titan is probably the best laboratory in the universe, while if the search is for actual extraterrestrial life, Enceladus probably gives you the best odds for your exploration dollar.

The public does not decide which NASA projects get funding, NASA does (except for a few big things mandated by congress). Nobody had a gun to their head and made them choose Mars 2020 or all of the others. In fact, with all of the craft we already have operating at Mars there's going to be a continuous stream of Mars news for the public for a long, long time. And really, what's been the biggest space stories of late, that show up say on the front page of Google News? New Horizons. Dawn. Rosetta. Cassini's latest flybies. The public likes pretty pictures and weird news, no matter where it comes from. And even congressional mandates these days are often for robotic probes to other worlds. When was the last time that congress mandated a probe to Mars like they did recently with the Europa probe mandate? They've insisted on general Mars policies, but nothing that specific in recent memory that I can recall.

Comment And the timeframe for getting another probe (Score 3, Interesting) 77

... to Titan will be approximately three weeks after never :P

Well, at least they're not planning to follow up the wasteful 2020 flagship to Mars with yet another flagship to Mars as part of their ongoing Mars obsession at the cost of the rest of the solar system.

There is never time to do it right, but always time to do it over.

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