Split Space Travel split from Military spending vs societal benefits

[Elixir]

* As long as you like penguin

…and seal, and krill and … what’s not to like?

 

[Shadowy Man]

Orbital mechanics doesn't work like that. Any location on the lunar surface can bombard Earth; It's just a matter of choosing the right trajectory to ensure capture by the Earth's gravitational well.

It's not enough to be captured -- the vast majority of launch trajectories that get captured will just go into elliptical orbits. The critical thing is to cancel out the moon's orbital velocity so the projectile escapes the moon with no angular momentum relative to Earth.

I would think an elliptical orbit that intercepts the Earth would be ok. I don’t think you would need to negate the entire angular momentum. However, I admit that ( without doing the numbers ) the difference may not be significant.

 

[Bomb#20]

Orbital mechanics doesn't work like that. Any location on the lunar surface can bombard Earth; It's just a matter of choosing the right trajectory to ensure capture by the Earth's gravitational well.

It's not enough to be captured -- the vast majority of launch trajectories that get captured will just go into elliptical orbits. The critical thing is to cancel out the moon's orbital velocity so the projectile escapes the moon with no angular momentum relative to Earth.

I would think an elliptical orbit that intercepts the Earth would be ok. I don’t think you would need to negate the entire angular momentum. However, I admit that ( without doing the numbers ) the difference may not be significant.

Right. The projectile hits Earth if perigee is less than Earth's radius, which is 1/60 the Earth-to-Moon distance. Angular momentum is conserved, so at perigee it's moving at least 60 times as fast as when it starts. Escape velocity is 11 km/sec, so it has to be going slower than that at perigee, so back-of-the-envelope, it has to start out at less than about 180 m/sec. The Moon's going around us at about 1000 m/sec, so you'd need to negate at least 82% of the angular momentum to drop anything on the Earth.

 

[bilby]

But is that high enough resolution to reconstruct the mind?!?! You need to know the interconnections of every neuron and how they work.

And you need to not only emulate nervous and synaptic activity, but also the wider endocrine environment that has (as usual) been ignored in this discussion.

You are not your brain; You are your brain in a soup of hormones (many of which are produced far away from the brain; And which are subject to various feedback loops both nervous and hormonal).

 

[Worldtraveller]

Also. For the same reason true AI will never happen under our current programming paradigm, the brain would be impossible to emulate in a hardware sim. The underlying programming would still be binary. That places more restrictions on what can actually be emulated than just about everything else.

 

[Loren Pechtel]

You can wrap a launcher (same concept as a maglev train) around the moon and

...every nation on the planet will have to cringe in fear of you bombarding their cities with impunity, from the ultimate high ground.

Oh, sorry, wasn't that where you were going with that thought?

You can bet that's where Vlad Putin would have gone.

You're thinking The Moon is a Harsh Mistress?

I was thinking of delta-v budgets. A lunar equator launcher can also be used to land things from grazing trajectories. Even if it doesn't land--lunar flyby, grabs the cable in passing and the launcher boosts it to whatever is desired before releasing it again.

 

[Loren Pechtel]

But what is the purpose of staying there anyway.

That should have had a question mark, dontcha think?

One purpose - ONE:
If you filled a dome with an appropriate atmosphere at 14-15 psi, and strapped on some (relatively small) wings,
YOU COULD FLY!* That makes it all worth it IMHO.

*(Assuming you're in fairly decent earthbound shape and not already acclimated to moon's gravity.)

I have some doubts about whether this would actually work. Yes, we have the strength, but do we have the means to apply that strength to flapping for flight? Birds have big wing flap muscles, our big muscles are in our legs.

I think AC Clarke did the math on that. If you can do about 15 push-ups, you should be able to lift off on arm strength alone. A fifth of my weight? Piece-o-cake! If there is a way to harness leg strength as well, the roof is the limit.

But how strong are we on a push-forward motion (wing flap down)??

Flight by something with your legs would certainly work--but it can be done on Earth. Albeit not flapping flight.

 

[Loren Pechtel]

I have some doubts about whether this would actually work. Yes, we have the strength, but do we have the means to apply that strength to flapping for flight? Birds have big wing flap muscles, our big muscles are in our legs.

You would have to generate ~1/6 of your Earth body weight to overcome gravity. If you weigh 120 lbs on Earth, that's 20 lbs of force. Should be doable.

Standing isn't the same thing as flapping flight.

 

[Loren Pechtel]

...every nation on the planet will have to cringe in fear of you bombarding their cities with impunity, from the ultimate high ground.

Put the business end of the launcher on the far (not "dark", sorry Pink Floyd!) side of the Moon.

Orbital mechanics doesn't work like that. Any location on the lunar surface can bombard Earth; It's just a matter of choosing the right trajectory to ensure capture by the Earth's gravitational well.

Launching from the far side makes it more difficult for your target to see the projectile launch, and requires them to monitor a big area of space around the Moon for incoming, rather than just observing the launch site.

Maglev launch won't leave much of a signature.

And while you can fire from farside that means long flight times (important in a military context) and it means you can't use the launcher to put more energy in your payload. The launcher I was picturing can hit more than 10x as hard as a simple fall--and with a flight time under three hours.

You can bet that's where Vlad Putin would have gone.

I guess he read TMiaHM too ...

Probably. It's a good story.

Except the numbers are so wildly wrong. I always find it jarring when the numbers don't come close to reality. His little retrorockets for landing would be similar to the Saturn V stack.

 

[Loren Pechtel]

...every nation on the planet will have to cringe in fear of you bombarding their cities with impunity, from the ultimate high ground.

Put the business end of the launcher on the far (not "dark", sorry Pink Floyd!) side of the Moon.

Orbital mechanics doesn't work like that. Any location on the lunar surface can bombard Earth; It's just a matter of choosing the right trajectory to ensure capture by the Earth's gravitational well.

Launching from the far side makes it more difficult for your target to see the projectile launch, and requires them to monitor a big area of space around the Moon for incoming, rather than just observing the launch site.

To launch deep space missions from the far side it would be best for the mass driver to launch west-to-east; in order to bombard Earth it would need to launch east-to-west. It should be pretty straightforward for the nations of Earth to observe the project from lunar orbit and see which way it's aimed.

I'm picturing one wrapped around the moon.

And for deep space you sometimes want the launcher to fire the other way--you need to shed energy to get to Venus or Mercury. Or something like the Parker probe. (We had to send it via Jupiter because a direct mission is out of the question.)

 

[Loren Pechtel]

Orbital mechanics doesn't work like that. Any location on the lunar surface can bombard Earth; It's just a matter of choosing the right trajectory to ensure capture by the Earth's gravitational well.

That is true. It's a more complex trajectory.

Launching from the far side makes it more difficult for your target to see the projectile launch, and requires them to monitor a big area of space around the Moon for incoming, rather than just observing the launch site.

Are the launchers trying to hit something specific or just wildly shooting? Because the more complex trajectory would also make it more difficult to hit anything specific.
Also, for deep space missions like Loren described, you need a lot of Δv. To hit something on Earth, you don't. So you don't even need the type of launcher Loren described to wage war against Earth.

However, you are right that control over the Moon would be very strategically important.

Yup. If I'm remembering the numbers right a team built a launcher with something like half the required speed. That could fit indoors even counting the capture system. While I'm not aware of anyone building something powerful enough there's no reason to think it won't scale well if you don't have a pesky atmosphere in the way.

Hitting Earth is easy, although throwing something big enough to actually do much is the real problem. To be a weapon it has to survive the passage through the atmosphere and retain a reasonable amount of energy in doing so. His 10kt rocks can't be done--they make a big fireball. A man-made projectile will hold up a lot better than what nature throws--but remember Chelyabinsk was half a megaton--and didn't get anywhere near the city. The only damage was windows and those too close to them. (Duck and cover is an appropriate response to a meteor, same as it is for a nuke.)

 

[Loren Pechtel]

Orbital mechanics doesn't work like that. Any location on the lunar surface can bombard Earth; It's just a matter of choosing the right trajectory to ensure capture by the Earth's gravitational well.

It's not enough to be captured -- the vast majority of launch trajectories that get captured will just go into elliptical orbits. The critical thing is to cancel out the moon's orbital velocity so the projectile escapes the moon with no angular momentum relative to Earth. Your best bet is to launch horizontally at 2.6 km/sec directly backwards from the moon's trajectory around Earth. Assuming a large immovable launcher, you should have a launch window once a month. Slight variations in the speed and the time of launch would allow targeting specific locations.

Actually, there's quite a range of acceptable launch trajectories. -2600m/s is simply the easiest. All you need is to get the periapsis fairly deep in the planet, you don't need to cancel all the orbital velocity.

Note, though, that your launcher can hit at anytime, there is no launch window. It does take a bit of variation to compensate for the moon's wiggles, though.

 

[Loren Pechtel]

Orbital mechanics doesn't work like that. Any location on the lunar surface can bombard Earth; It's just a matter of choosing the right trajectory to ensure capture by the Earth's gravitational well.

It's not enough to be captured -- the vast majority of launch trajectories that get captured will just go into elliptical orbits. The critical thing is to cancel out the moon's orbital velocity so the projectile escapes the moon with no angular momentum relative to Earth.

I would think an elliptical orbit that intercepts the Earth would be ok. I don’t think you would need to negate the entire angular momentum. However, I admit that ( without doing the numbers ) the difference may not be significant.

The numbers are fairly close. When you're that far out very small changes to your velocity make big effects in where your periapsis is. And likewise, plane changes are pretty cheap out there. However, you are not limited to trajectories with the moon at the apoapsis and the periapsis in the planet. Orbital mechanics requires that the launcher be a point on the orbit (ignoring the deflection caused by the moon's gravity) but it doesn't require it to be the apoapsis--and two points do not define an ellipse. (You don't get infinite points, though--go too far from the Earth and the Sun will likely take your rock away.)

 

[Loren Pechtel]

But is that high enough resolution to reconstruct the mind?!?! You need to know the interconnections of every neuron and how they work.

And you need to not only emulate nervous and synaptic activity, but also the wider endocrine environment that has (as usual) been ignored in this discussion.

You are not your brain; You are your brain in a soup of hormones (many of which are produced far away from the brain; And which are subject to various feedback loops both nervous and hormonal).

I think they'll be a lot easier to simulate.

But note that for hormones to influence the mind there must be some interaction between hormones and neurons. Your model needs that.

 

[Bomb#20]

I have some doubts about whether this would actually work. Yes, we have the strength, but do we have the means to apply that strength to flapping for flight? Birds have big wing flap muscles, our big muscles are in our legs.

I think AC Clarke did the math on that. If you can do about 15 push-ups, you should be able to lift off on arm strength alone. A fifth of my weight? Piece-o-cake! If there is a way to harness leg strength as well, the roof is the limit.

But how strong are we on a push-forward motion (wing flap down)??

Flight by something with your legs would certainly work--but it can be done on Earth. Albeit not flapping flight.

Yes, even flapping flight!

UTIAS Snowbird - Wikipedia

en.wikipedia.org

 

[Bomb#20]

It's not enough to be captured -- the vast majority of launch trajectories that get captured will just go into elliptical orbits. The critical thing is to cancel out the moon's orbital velocity so the projectile escapes the moon with no angular momentum relative to Earth. Your best bet is to launch horizontally at 2.6 km/sec directly backwards from the moon's trajectory around Earth. Assuming a large immovable launcher, you should have a launch window once a month. Slight variations in the speed and the time of launch would allow targeting specific locations.

Actually, there's quite a range of acceptable launch trajectories. -2600m/s is simply the easiest. All you need is to get the periapsis fairly deep in the planet, you don't need to cancel all the orbital velocity.

Note, though, that your launcher can hit at anytime, there is no launch window. It does take a bit of variation to compensate for the moon's wiggles, though.

The moon's axis of rotation is out of alignment with its orbit by about 7 degrees. That's enough that at most times of the month even if you cancel out the moon's revolution you only nail the east-west aim; the projectile still flies past the Earth thousands of km to the north or south. Since the launcher is fixed the direction of the shot is fixed, while the Earth goes back and forth across your virtual bombsight on a one month cycle. So you have to time your shot for when it's in the crosshairs. (Which means I should have said you get a launch window twice a month.)

 

[Emily Lake]

Not only do I think that's some sort of life, it's the sort of life I'm looking forward to, with not having to bother with maintaining so much meat all the time.

I think you're severely underestimating the impact the meat has on your brain. At a minimum, the role of sensory perception on cognitive function is pretty massive... and that's not even considering the interaction between sensory perception and emotion - and how that affects cognition.

Our brains are meat. Without the meat, we have no mind.

 

[Emily Lake]

Colonisation of space is completely impractical.

I would say closer to impossible.

I would say neither of those things is actually true. There are plenty of people in the world who are ready and willing to give up a humanoid body in exchange for a form factor that could very well operate in space, and technology is getting closer every day to allow achieving that.

As soon as you punt on demanding a human body to be part of the mix, concepts like food water and air become completely superfluous.

Will it happen in the next year? Probably not. But it will almost certainly happen in the next 5-10 years.

I'll take that bet.

I'm thinking more like 500 to 1000 years... and I think I'm being optimistic in that estimate.

 

[Emily Lake]

We already have a good understanding on whole systems running in parallel. That's literally how every modern AI works.

We don't have anywhere near a comprehensive understanding of how our own minds work. And modern AI is not at all I. It's sophisticated and "trainable", but there's no actual intelligence involved yet.

 

[Emily Lake]

There is no defining material "you"; you is a pattern, not an object. The material you is a ship of theseus; All of the components are replacable, without any effect on the self.

I challenge this assumption. We know from observation that brain injuries can fundamentally change a person's behavior and personality. We might be able to replace some components - a heart, a kidney, an eye - but we're not even remotely close to being able to perform even a partial brain transplant. And I strongly suspect that if we could replace a portion of someone's brain, they would not be the same 'person' in any reasonable sense of the word - enough of their fundamental mind would be gone to make them a different person.