tomf

The maximum change in velocity is going to occur when you change direction by exactly 180°, i.e. the the orbit at the SOI crossover is parallel to the centre line. This can only happen when the orbit is in fact an ellipse cut off by the SOI meaning that the relative velocity is always low. For hyperbolic orbits the deflection angle is always less, but it is at a maximum when the pe of the orbit skims the surface/atmosphere. For a given relative velocity you can work out the maximum angle of deflection and hence the maximum change in velocity. If you can only deflect 90° at a given relative speed of V then your Delta v is ✓2 * V by simple trig. This matches the observations above. - a massive body is good, it deflects more at a given speed - a denser body is better, pe can be lower giving more deflection - If the speed is to high deflection angle is low giving little DV It's bedtime here which is definitely the only reason I'm not going to do it but it ought to be possible to work out for any given body what relative speed gives the highest change. ---------------- Working out how to get the Delta v to point in a useful direction is an entirely different matter in my experience.

Well it has taken all human industrial capacity for the last 200 years to move the climate by a few degrees over the next 60 years so no one said climate change was easy.

If you look at the pork chop plot you can pick your departure date on the horizontal axis, and the arrival date on the vertical and it will tell you how much Delta v you need, so if you have the Delta v and you pick an arrival date before the first crafts arrival date the later craft will overtake

https://what-if.xkcd.com/24 That design is what you get when your ISP isn't really good enough

For the suits question it's going to come down to the types of damage typically sustained by the ships. Of you ships frequently end up after a fight with lots of small holes from being blasted for example with orbital velocity shrapnel, or ships go "down" slowly enough that you have time to get to a lifeboat then suits are going to be recommended. If weaponry is such that ships tend to face total existence failure and help is far away then you may as well be comfortable in shirt sleeves.

A while ago I asked a doctor about ventilators and leaned that about 0.03 bar of overpressure is typical. Breathing pure oxygen you need at least 0.18 bar. Given that the pressure on Mars is only 0.0061 we still need around 0.15 bar of pressure applied to the chest

Do we know what the rentry timings will be line? If starships profile is anything like the f9 first stage you have two minutes between rentry burn and landing which doesn't seem a lot of time to target it with heavy weaponry. And it spends most of that time hypersonic so good luck trying to hit it with small arms fire.

Sounds fun, do you have a link for the thread?

I listened to a podcast a few years back which looked at time use surveys and concluded that washing machines made much less difference than you might think, basically people wore clothes for longer before washing them, used detachable collars, dark colours to hide dirt etc. The thing that really made a difference was pre prepared food. The average food preparation time for a household in the 60s was around 4h a day, now it is 45m. We were willing to be a bit grubby but not too starve. The BBC did a great series called "50 things that changed the modern economy" that I had to re-listen to to write this

Deer are already pretty good at being deer, for every conceivable mutation that might make then into better deer there must be millions that make for a worse deer. Also evolution doesn't work on the survival of individuals, it works on genes. Genes that promote the survival of other members of your species over the individual can work on the basis that the others are likely to have the same gene.

If your water is already at 100°c then you need to supply the vaporisation enthalpy. The Wikipedia link gives 2257J/g so you need 50*2257 j/s or 11kW https://en.m.wikipedia.org/wiki/Enthalpy_of_vaporization

For pretty much any record that you can set out to achieve the difficulty in achieving it is going to be pretty proportional to the coolness of having achieved it + any actual usefulness. If a record were cool/useful and easy someone would have done it already and pushed the boundary further out. So by that measure I would expect the submarine record to be easiest simply because it is the least "cool"

When I was a child I bought a present for a friend which was basically an enormous black plastic bag and a light string, you filled the bag with air and waited for it to take off.

Question Inspired by that post but that star just has some uranium in its atmosphere.

Could you have a "star" made entirely of uranium? Somehow a cloud of uranium isotope ratio TBD collapses and forms an object that emits roughly the same power as the sun for an appreciable length of time. A reasonable proportion of the energy needs to come from fission rather than just gravitational collapse a-la https://en.m.wikipedia.org/wiki/Kelvin–Helmholtz_mechanism I think an equivalent question is Is there a negative feedback mechanism in the collapse of a cloud of uranium that will result in a steady power output.

Colossus wasn't particularly influential though because it was kept secret for 30 years. After the war Britain and the US continued to recommend enigma to other governments a a "secure" encryption system

Derailing the thread somewhat but here we go. The assassination at the end of look to windward is much discussed as evidence that the culture is not perfectly benign. It is an act of revenge against an attempt to kill billions of culture citizens and although fairly well targeted against those responsible it is gratuitously spectacularly overkill as a deliberate message. The series illustrates a point that people have tried to make several times before. Banks doesn't care how his FTL travel works, or the details of weaponry used. The best way to create great sci-fi is to create engaging characters and relatable situations.

Nowhere in the novels is there any kind of mood control or suppression of free will. The author certainly intended the culture to be a utopia. Almost all the citizens appear to lead happy, healthy and fulfilled lives. The few that don't are the subject to the novels plots of good their society tries to help them. I'd definitely take that over any other real or fictional society I've heard of.

For a classic version of a post money society you should read Iain M Banks's culture, and somewhere online there is an interesting essay on which he explains his reasoning.

Ok I over simplified for to make my point, I meant it was a dive with no mandatory decompression, I do of course do a safety stop on every dive, and as for what counts as recreational diving that depends on what agency you train with. My point was that a blame culture around DCI leads to dangerous denialism. It can happen on any dive but is extremely unlikely to do long term harm unless you have seriously overstepped. I have seen multiple cases of people with clear symptoms who have been unwilling to believe them because "everything was ok on the dive". All of them were completely fine after treatment.

If you have a cave diving ticket I would say the best diving in the world is the caves on the mainland opposite. It's a dangerous myth that you can only get DCI if you have done something wrong, it tends to cause people to deny their symptoms because they don't want to be thought at fault. Both my bends came after dives that had gone perfectly to plan, the first after a 50m dive with ~40 minutes of decompression, the second after a 25 min no stop dive to 20m

You would have to be spectacularly unlucky to get fatal DCI from the type of diving I am sure the Saint was doing, whereas even a mild reaction to stonefish, which is rarely fatal on its own is going to be extremely hazardous under water. (Source: been bent twice) Bends can be treated, drowning not so much

Or you could go whole hog and invent smart wheels as on YT's skateboard in snow crash where the room of the wheels are made from individual rubber pads on extendable spokes to cope with any terrain. I guess they wouldn't be quite as good at stepping over obstacles but could be smoother and faster

How would gravitational lensing be useful for a telescope? The Wikipedia page starts by saying that it doesn't act as a focusing lens at all and light from a point is smeared to a line but then talks about the solar gravitational lensing.

The Wikipedia page on luciferase says the bacterial version is 80-90% efficient, so I assume the humanoid version could be similar. https://en.wikipedia.org/wiki/Luciferase#:~:text=The reaction is 80% to,input energy to visible light.