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Loren Pechtel

 Discussion on question by www: If hum…

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Loren Pechtel
Jun 16, 2024 03:35
@SimonCrase "My" aliens? To give a scale on which they operated--Earth doesn't have a moon anymore. The object in our sky is one of their ships, hidden beneath a thick later of the original moon.
Loren Pechtel
Jun 16, 2024 03:35
@SimonCrase Or how about David Weber's Dahak series. Humanity didn't evolve on Earth but the ecosystems match because Earth life is mostly what was reseeded by the aliens (homo sapiens) after past extinction events.
Loren Pechtel
Jun 16, 2024 03:35
@RobertRapplean Even if you could get around the educational problem (and it would be a showstopper for 2024 tech) you have the problem that there will be nobody to fill any position that you need less than one in a couple million of.
 

 Discussion on answer by Harper - Rein…

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Loren Pechtel
Jun 6, 2024 12:31
@Harper-ReinstateMonica First minute, you are right. The point is that there is a use case for having both a main system and point of use tankless systems assuming the point of use systems can control their output temperature properly given varying input.
Loren Pechtel
Jun 6, 2024 12:31
You're assuming the two are equal. If the water heater is electric you are right, having both a water heater and a tankless unit is completely redundant. But what if the main one is gas or solar?
 

 Discussion on answer by Robert Rapple…

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Loren Pechtel
Jun 6, 2024 02:00
As for bomb-pumped lasers--everyone seems to ignore the pointing system. You laser rod has to be aimed very precisely as it's an unguided weapon. It will need it's own telescope and vibration will be a really big deal in a real world situation.
Loren Pechtel
Jun 6, 2024 02:00
And note that since it's very fast you can get rid of something like half the energy with a sheet of aluminum foil. Vaporized, half the energy is radiated out rather than in.
 

 Discussion on question by user110391:…

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Loren Pechtel
May 9, 2024 16:17
@JeremyFriesner And there's also an intermediate scenario--if we were faced with a rock that we could deflect only with tremendous effort I would expect it to fail because too many corners were cut.
 

 Discussion on answer by Monty Wild: R…

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Loren Pechtel
Sep 25, 2023 04:45
One objection here--I see nothing in this that indicates what mass the energy is deposited into. Your ejection volume is based on how much it could throw off the moon, not how much it will throw. It could throw less mass faster, it could throw more mass slower--and not escape. If the energy doesn't show up as spall a lot of it will go into changing the moon's orbit.
 

 Discussion on answer by Robert Rapple…

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Loren Pechtel
Aug 5, 2023 20:50
Many comments are addressing using multiple points of initiation--but this gets into thorny issues of just how precise the timing of your detonator is. I know the government is careful with detonators that have high precision because they're needed for nukes. I know nothing of the details, though.
 

 Discussion on question by ArktourosUl…

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Loren Pechtel
Mar 22, 2023 14:28
BIG problem here--when the star relights the inhabitants die.
Loren Pechtel
Mar 22, 2023 14:28
@ZeissIkon It's also not used for bombs because you can't get much of a boom no matter how much of it you try to pile up. Once you have piled up a critical mass it starts reacting, heats up and disassembles the mass. There's simply no way to pile up enough to get a good boom out of it. Chernobyl, not Hiroshima.
 

 Discussion on question by uhoh: What …

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Loren Pechtel
Mar 8, 2023 20:05
@OrganicMarble If the data on the Wikipedia page is right the Shuttle would have a wing loading of 274 kg/m^2 (empty). 1% of what he's suggesting for a Karman plane, of course it was ignored. (The page lists wing area, I don't know if that includes the area underneath the orbiter..)
 

 Discussion on answer by Nepene Nep: M…

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Loren Pechtel
Feb 24, 2023 03:46
@JBH At a scale 1000x bigger than the chips that run our systems. And note that he's using old equipment--it's very unlikely that he can build the equipment he's using.
Loren Pechtel
Feb 24, 2023 03:46
@JBH A quick approximation on what they can have: Look at the prevalence of X in society. If it's less than one X per 200,000 people it's going to strain their society to do it--and note the calamity of X is essential and breaks. Realistically, you need more than one so figure 1 in 100,000. Chip fabricators are 1 per many millions--they're gone.
 

 Discussion on answer by John O: Max t…

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Loren Pechtel
Feb 23, 2023 19:24
@KeithMorrison Manure isn't viable fertilizer at the level of society.
Loren Pechtel
Feb 23, 2023 19:24
@KeithMorrison Those modern seeds require modern fertilizer. Now you need the whole fertilizer infrastructure.
 

 Discussion on answer by Daron: What d…

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Loren Pechtel
Feb 2, 2023 20:28
The air is moving at 20km/sec relative to the portal. Entering the portal will not change this.
 

 Discussion on question by Kevin Kostl…

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Loren Pechtel
Jan 28, 2023 08:37
@EricDuminil Note that the previous line says the rat is killed. Saying the man is broken is adding to this, the man will have broken bones that will alter his shape.
 

 Discussion on question by Interdimens…

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Loren Pechtel
Jan 27, 2023 20:38
@JBH You use it for it's designed purpose--look at the novel he's basing the sail on. Once they arrive they use the sail to get around the star system. The laser pump gives you a lot more acceleration but it's still useful just driven by a star.
Loren Pechtel
Jan 27, 2023 20:38
@JBH There's a good chance the sail doesn't survive a planetary landing for chemical reasons. Other than the reinforcements they're also extremely delicate--you want them as thin as possible, they'll make tissue paper look robust.
 

 Discussion on answer by Zeiss Ikon: A…

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Loren Pechtel
Jan 27, 2023 20:38
@ZeissIkon Sticking the sail on a lander won't work--the sail can't stop itself, let alone any payload.
Loren Pechtel
Jan 27, 2023 20:38
Try to barrel into the star to slow and you'll find yourself hitting it at pretty close to half of lightspeed. Long ago I played with the numbers on using a star for aerocapture maneuvers like this--and they make artillery shells (the toughest machines humans build) look downright placid.
 

 Discussion on answer by gerrit: Any r…

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Loren Pechtel
Jan 26, 2023 17:52
@TylerH Because water doesn't always need filtering. When I encounter flowing water it's always clear. That doesn't make it safe to drink, though.
Loren Pechtel
Jan 26, 2023 17:52
@TylerH The water treatment we carry does nothing about chemical contamination. It's all about debris and biological hazards. Plenty of places will have water clear enough that debris isn't an issue, but there's always a biological risk.
 

 Discussion on question by merrygosqua…

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Loren Pechtel
Jan 10, 2023 02:41
How much selection bias is going on here? Patients who have weight-related issues are more likely to want to lose weight. They're also more likely to have bad things happen.
 

 Discussion on question by user2284570…

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Loren Pechtel
Dec 27, 2022 03:49
The area would be completely uninhabitable long before this point is reached. Death comes from the body's inability to cool itself long before condensation matters. And it comes much faster than a month.
 

 Discussion on question by forest: How…

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Loren Pechtel
Nov 29, 2022 03:09
What can he bring? Can he bring a year's worth of nutritional supplements? If he can't nutrition will be a survival limit.
 

 Discussion on question by JANXOL: How…

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Loren Pechtel
Nov 9, 2022 03:48
With small mammals being carriers there's simply no way to keep it out. Consider rabies--such a society has no defense beyond the fact that the R0 of human rabies is about zero. Vampirism has a high R0.
 

 Discussion on question by ebinbenis: …

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Loren Pechtel
Oct 27, 2022 15:16
@sphennings Most of those are actually fighter + something. The question is after pure fighters. Air superiority vs interceptor comes down to the tactical situation--my basic point is that you don't need anything different to shoot at flying monsters than flying aircraft.
Loren Pechtel
Oct 27, 2022 15:16
Fighters are fighters. All that's going to matter are sensors and countermeasures, things which did not exist in the timeframe you specify.
 

 Discussion on question by jkelly80: W…

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Loren Pechtel
Oct 23, 2022 06:40
I'm going to second Joel Etherton's comment--while I've never had an occasion to wear steel toed boots I do frequently wear hiking boots. They add weight and they considerably decrease your sense of what you're standing on--and that became a non-issue to me in a matter of a few miles. Admittedly, I've never worn them up a ladder.
 

 Discussion on answer by phyrfox: Do t…

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Loren Pechtel
Sep 13, 2022 01:07
I'll second the hand-watering one actually being a law that prohibits automated watering under certain conditions for water conservation reasons. I can hand-water newly-planted stuff in situations where I would not be permitted automated watering.
 

 Discussion on answer by JBH: Under wh…

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Loren Pechtel
Sep 6, 2022 09:51
Disagree--while you are right that the weapons are generally invisible that doesn't mean weapon hits are invisible. Against a night sky it doesn't matter that they're below one "pixel" that the eye can see--observers won't see the ships but they will see the light show.
 

 Discussion on question by Mindwin: Wh…

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Loren Pechtel
Aug 26, 2022 03:21
@Pelinore Yeah, an airship--except she's going to have a much lower maximum velocity and thus much less able to cope with winds. She's also far more vulnerable to gusts. I very much doubt she can safely go outside other than in pretty calm air.
Loren Pechtel
Aug 25, 2022 15:35
@Pelinore I don't believe you could produce remotely enough thrust waving a broom. While I agree she can fly she needs something far more effective than a broom to do so. However, she can't safely fly--she has far too great a cross section and will have serious problems with any breeze.
 

 Discussion on answer by Pelinore: Wha…

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Loren Pechtel
Jul 14, 2022 03:29
@Nosajimiki The only way I see to do it without alerting the target is to aim your lightsail at something near (in terms of angle) your target. Your target will still see the boost but won't realize the true target. After boosting the sail tacks towards the target, at this point the reflected energy is pointed away from the target.
Loren Pechtel
Jul 14, 2022 03:29
@Nosajimiki Laser-pumped lightsail is the only thing we can reasonably project that can deliver .5c. The basic problem here is that you have no hope of confining the drive beam to only hit the sail, some of the energy will spill--and that energy it pointed awfully close to your target. They'll know something's coming.
Loren Pechtel
Jul 14, 2022 03:29
@Nosajimiki A relativistic cannon is a major handwave. It has to be awfully efficient to avoid simply vaporizing the projectile.
Loren Pechtel
Jul 14, 2022 03:29
Note that the threat of return fire implies the target is at a similar tech level. You don't try to kill a planet that hosts a K2 civilization because there are bound to be a lot of survivors who are probably going to shoot back if they can figure out what to shoot back at.
Loren Pechtel
Jul 14, 2022 03:29
@Nosajimiki It's not seeking the RKEW, but seeing it's drive.
 

 Discussion on question by BenRW: 24 h…

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Loren Pechtel
Jun 13, 2022 16:47
There are going to be more nukes. They have 23 hours to modify some ICBMs to detonate when they are very close and hope they can guide them adequately. While they can't hope to stop it even one hit would almost certainly make a big reduction in the damage. Your rock is small enough that blowing it up will greatly increase the amount of energy liberated in the upper atmosphere rather than on the surface.
 

 Discussion on question by Skallod: Ho…

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Loren Pechtel
May 26, 2022 11:24
And what about the damage done going to vacuum in the first place? What you're worried about on return will have already caused great damage when they went up!
 

 Discussion on answer by nvoigt: Team …

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Loren Pechtel
May 17, 2022 23:41
@Neinstein Management is requiring people to return but there is no indication whether that actually has any bearing on the work performed. Many people have responded to the situation by trying to erase all outward signs of the pandemic as if that will magically stop people from dying of it.
 

 Discussion on question by Brinstar77:…

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Loren Pechtel
Apr 21, 2022 16:17
@user253751 To get capture around Earth you only have Luna to do it with. You need 13 km/sec to get capture of an object that is just barely interstellar. Luna can't come close to doing that. If you want capture from interstellar space you need multiple planetary encounters first.
 

 Discussion on question by Elias Kasap…

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Loren Pechtel
Apr 8, 2022 08:16
You're importing them and the value is almost certainly beyond what you're allowed to import without duty. Personal use means you either use up the product or take it back with you when you leave.
 

 Discussion on answer by nvoigt: What …

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Loren Pechtel
Mar 3, 2022 22:11
Another problem with using delivered = notified is what happens when multiple entities have access to that mailbox? While it would be unlikely to be a problem in the business world, what about divorce actions? Send the notice, get it out of the mailbox, the recipient has no knowledge of the legal action. And what if they truly weren't there? I've gotten a jury summons just before an international trip--with an appearance date before we got back. Had it come one day later it would have been sitting in the post office on the day I was to show up.
 

 Discussion on answer by pinegulf: Did…

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Loren Pechtel
Feb 11, 2022 15:03
@dan-klasson Very light fabrics have proven worse than useless--they actually help the virus spread.
 

 Discussion on question by matt_black:…

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Loren Pechtel
Jan 8, 2022 00:13
@matt_black Unfortunately, a lot of research does not do a decent job of controlling for even obvious factors.
 

 Discussion on answer by J. Murray: Do…

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Loren Pechtel
Dec 22, 2021 16:18
Nitpick: It's actually easier to breathe with increasing altitude. What's harder is getting enough oxygen.