DAL59

Serious Scientific Answers to Absurd Hypothetical questions

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36 minutes ago, kerbiloid said:

An expendable or a reusable species?

One per every cerebral hemisphere.

So, 7 cerebral hemispheres.

With 7 eyes.

Eyes in the back of my head would be capital!

There's actually ongoing research for that sort of stuff, I helped out a bit with research on biocompatible electrical interconnects to neurons about a decade back. It's a bit invasive for the general public to use, but technology-wise it's not that far out now. Spare hemispheres, maybe a little further... Albeit just as necessary in my case!

astrocyte.png
CNS neuron coupling to nanoporous gold electrical interface, work by Dr. E. Seker et. al

Also, technically a reuseable species, but it costs more to refurbish a unit than to just make a new one like on the STS :rolleyes: . Being flippant, don't take too seriously, please!

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Posted (edited)
12 hours ago, Cunjo Carl said:

Spare hemispheres, maybe a little further...

Btw, maybe it should be an atomic unit: a single hemisphere with an eye and an arm.

Most of animals are designed in dual mode, as it gives both stereo vision and redundancy.

But for a complex (and further hivemind) system maybe it's better to design the sapient beings in the multiplex mode: an arbitrary pack of such atomic units?..
Kinda a pack of mini-canadarms: arm+eye on one end, "leg" on another one, a capsule with the single-hemisphere brain in between, and a docking port with connectors instead of the foot .

Then we can also rearrange the atomic units according to everyone's current needs.

Edited by kerbiloid

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So, there were on and off plans for decades to use Masers and IR Lasers and things to beam energy from satellites down to Earth. Could we use the same techniques to beam energy from Earth up to a lunar base? That'd be pretty neat.

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Posted (edited)

1000 GW Earth-to-Moon emitter with 1% atmospheric loss = 10 GW torch heating the air.

Sending the ray from LEO station unlikely has any advantage over the same station in LLO or L-point.

So, I guess, either send the ray from an LSO emitter, or place the reactor right on the Moon.

Edited by kerbiloid

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No atmosphere on the moon also means much better solar performance. And maybe a station out in orbit beaming solar energy down.

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11 hours ago, Cunjo Carl said:

So, there were on and off plans for decades to use Masers and IR Lasers and things to beam energy from satellites down to Earth. Could we use the same techniques to beam energy from Earth up to a lunar base? That'd be pretty neat.

If you can build giant lasers on earth and receivers on the moon, it's hard to imagine not being able to produce solar panels on the moon. Especially if a lunar colony is on the poles, since you would have continuous power.

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Posted (edited)
1 hour ago, Mad Rocket Scientist said:

If you can build giant lasers on earth and receivers on the moon, it's hard to imagine not being able to produce solar panels on the moon. Especially if a lunar colony is on the poles, since you would have continuous power.

Well, the moon rotates around at a rate of 1/month, which is really inconvenient for moon bases near the poles because the sun will appear to be spinning very slowly around the horizon. So that means the solar panels would both need to be nearly vertical, and also either rotate to face the sun (= complex and heavy), or be only 1/pi (30%-ish) efficient at collecting light, let alone converting. And we'd also need days worth of maintenance batteries for whenever you do wind up in shadow if your base isn't literally on a small mountain at the exact pole. The upside is, solar panels can be made very easily in the lunar environment by simply evaporating small amounts of solar panel materials and allowing them to condense on prepared surfaces, but preparing enough large areas of flat, smooth slanted ground for say a small testbed 100kW ISRU operation would be hard. Meanwhile, Earth-based lasers could (maybe) provide orders of magnitude higher irradiance while being mostly stationary in the sky, allowing the collectors to be much smaller and simpler. So, that's the reasoning behind thinking along this silly line of thought. Given these benefits, what would it take to make it happen?

Edit: Just to be clear, I suspect the 1MW death lasers required to make this happen will be entirely impractical, which is why I posed the question here. But from the Moon base's perspective, I believe it would be easier than collecting sunlight.

 

11 hours ago, kerbiloid said:

1000 GW Earth-to-Moon emitter with 1% atmospheric loss = 10 GW torch heating the air.

Sending the ray from LEO station unlikely has any advantage over the same station in LLO or L-point.

So, I guess, either send the ray from an LSO emitter, or place the reactor right on the Moon.

 

I guess, when it comes down to it, I really want an excuse to shoot high power lasers at the moon. To this end, I can consider burning holes in the sky only a positive thing, Kerbiloid! :cool:

Edited by Cunjo Carl

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5 minutes ago, Cunjo Carl said:

Well, the sun rotates around at a rate of 1/month, which is really inconvenient given it'll appear to be spinning very slowly around the horizon to a moon base near the poles. So that means your solar panels would both need to be nearly vertical, and also either rotate to face the sun (= complex and heavy), or be only 1/pi (30%-ish) efficient at collecting light, let alone converting. And you'd also need days worth of maintenance batteries for whenever you do wind up in shadow if your base isn't literally on a small mountain at the exact pole. The upside is, solar panels can be made very easily in the lunar environment by simply evaporating small amounts of solar panel materials and allowing them to condense on prepared surfaces, but preparing enough large areas of flat, smooth slanted ground for say a small testbed 100kW ISRU operation would be hard. Meanwhile, Earth-based lasers could (maybe) have orders of magnitude higher irradiance while being mostly stationary in the sky. So, that's the reasoning behind thinking along this silly line of thought. Given these benefits, what would it take to make it happen?

Slow rotation doesn't seem that complex to me, especially in 1/6th gravity. Another option would be to use something like an inverted cone covered in mirrors so light was always reflected down onto stationary solar panels. Something like that, or vertical greenhouses, would be required for food anyway, since plants require so much energy.

5 minutes ago, Cunjo Carl said:

Edit: Just to be clear, I suspect the 1MW death lasers required to make this happen will be entirely impractical, which is why I posed the question here. But from the Moon base's perspective, I believe it would be easier than collecting sunlight.

I guess, when it comes down to it, I really want an excuse to shoot high power lasers at the moon. To this end, I can consider burning holes in the sky only a positive thing, Kerbiloid! :cool:

I think we can all agree on that.

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43 minutes ago, Cunjo Carl said:

To this end, I can consider burning holes in the sky only a positive thing, Kerbiloid!

The way to check if the sky is solid.

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13 hours ago, kerbiloid said:

1000 GW Earth-to-Moon emitter with 1% atmospheric loss = 10 GW torch heating the air.

The eco-enthusiasts already have a problem with wind mills chopping up birds.   Imagine a pillar of fiery death in the sky. 

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On 4/19/2019 at 8:58 PM, Gargamel said:

Imagine a pillar of fiery death in the sky. 

I think that'll be a good name for my debut album.

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Say you have a scifi spaceship that can shield itself from the effects of gravity.

Your ship still uses rocket engines though to reach space, and a jump drive to cover vast distances in space that only works in outer space.

With gravity reentry is a dangerous affair if you're orbiting. What about when the ship chooses to shield itself from gravity though?

Reasons for this would be to conserve fuel, since I reckon that an orbital speed weightless object would be slowed faster in the atmosphere than if gravity was on, since gravity tends to accelerate you down in sync as your orbital momentum is slowed.

I do not know if the g-forces would be less or more than normal during reentry with the gravity shield up.

If I had to guess I would say that it migjt be either similar to g-force of normal reentry or perhaps more, at least initially.

Since a weightess object smacking into atmosphere at orbital speeds I think sould be slowed down dramtically.

 

What do you think? I am only guessing.

 

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Gravity would not be much an factor during reentry. See in KSP you fly vertical during most of the reentry heating. 

If you go straight down you fill face enormous g forces because the rapid braking once you reach the thick atmosphere, you would not accelerate going down but still go fast if you are moving at orbital Speed

If returning from orbit you could however stay longer the upper atmosphere for an gentler reentry simply by activating the shield this would raise your orbit. 

This would also be how you take off with this ship. Simply activate the shield, do an burn and you will move upward, length of burn depend on how long time you want to spend getting into an high orbit. 
Say you stay subsonic until out of atmosphere and then 1 Km/s 10 secound later you pass GEO, 100 hour to the moon, here you might want to turn off the shield for an gravity assist. 
As you see you can abuse this in pretty wild ways getting away from stuff is always free but you need energy to gain speed, best way to get to orbit would be to do an moon gravity assist who send you back to earth, then use aerobraking to get into orbit. 

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Posted (edited)

Thanks. I was thinking that saucer shaped ships may make more sense here, so long they used atmospheric plasma rockets (using atmosphere air as propellant by running it over hot engine reactor core) at least until they the air was too thin and they have to switch to stored propellant rockets.

Smaller millennium falcon size ones would be practical. Massive kirk-era enterprise ones, would also work, 

So long they use some type of thermal atmospheric engine to not waste fuel during launch because of atmospheric friction. 

Edited by Spacescifi
Missed a few words

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Interesting question! I will assume the antigravity shield is the only fantasy element in this scenario, and that the ship is approaching the planet's atmosphere at orbital velocity or greater. Therefore we must still contend with aerobraking and aerodynamic heating while entering the atmosphere

6 hours ago, Spacescifi said:

What about when the ship chooses to shield itself from gravity though?

If the ship does not feel the pull of a planet's gravity, then it cannot be in orbit around that planet, Therefore, it must approach the planet directly, otherwise it would just sail straight off into space.

  • A direct, high speed reentry will generate huge negative acceleration, (especially if the antigravity mechanic works by negating mass while retaining the large surface area of the spacecraft).
  • There will also be a lot of heating from air friction. (If the mass of the ship is negated, where does this heat go?)
  • 4 hours ago, magnemoe said:

    If returning from orbit you could however stay longer the upper atmosphere for an gentler reentry simply by activating the shield this would raise your orbit. 

    But in this case you have to then use propulsion to direct yourself back at the planet, or go sailing straight back into space.

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8 minutes ago, Nightside said:

Interesting question! I will assume the antigravity shield is the only fantasy element in this scenario, and that the ship is approaching the planet's atmosphere at orbital velocity or greater. Therefore we must still contend with aerobraking and aerodynamic heating while entering the atmosphere

If the ship does not feel the pull of a planet's gravity, then it cannot be in orbit around that planet, Therefore, it must approach the planet directly, otherwise it would just sail straight off into space.

  • A direct, high speed reentry will generate huge negative acceleration, (especially if the antigravity mechanic works by negating mass while retaining the large surface area of the spacecraft).
  • There will also be a lot of heating from air friction. (If the mass of the ship is negated, where does this heat go?)
  • But in this case you have to then use propulsion to direct yourself back at the planet, or go sailing straight back into space.

I think the most effective way woukd be to switch the gravity shield off once enough orbital momentum was bleed off.

Indeed, you could do some deep dives into atmosphere this way and slow rapidly. I would only slow enough so that the ship can be falling straight down, even if I have to switch the grav-shield off a few times. Then for landing I would turn the grav-shield on and slow my descent much faster than normal with rocket and air friction assist.

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13 minutes ago, Nightside said:

A direct, high speed reentry will generate huge negative acceleration, (especially if the antigravity mechanic works by negating mass while retaining the large surface area of the spacecraft).

I fixed this in my hand-wavey space opera with a simple throwaway line. Something along the lines of "The antigrav lowers our weight, not our momentum."

Let the technicians figure it out. I got a story to write :D

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Posted (edited)
3 minutes ago, 5thHorseman said:

I fixed this in my hand-wavey space opera with a simple throwaway line. Something along the lines of "The antigrav lowers our weight, not our momentum."

Let the technicians figure it out. I got a story to write :D

Or to be more precise, it would eliminate your weight altogether if it shielded it from gravity totally.

At least it makes many scifi ships practical instead of rocket shapes beating any and everything all the time like in IRL.

Edited by Spacescifi

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If you want to make reentry easier then I would recommend either using active cooling or using your powerful propulsion system to cancel most of the orbital velocity, reducing the effect of gravity isn’t all that helpful in this situation.

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If a ship can avoid experiencing gravity it can maintain an orbital altitude without an orbital velocity. In fact, it *needs* to experience gravity in order to orbit, because without gravity any velocity is escape velocity unless you apply constant radial thrust. A gravity manipulating ship doesn't have to orbit unless it wants to. It levitates.

So there's no reason its entry to the atmosphere needs to be great other than reducing transit time. If you can sustain re-entry heating, come in hot. If not, walking pace or slower will do.

Without gravity all urgency goes away.

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Without gravity, gforce is whatever you want it to be.

with nothing to pull you into denser atmosphere, you can use aerodynamics to choose to either stay in upper atmosphere slowly bleeding speed and "flying" downwards to keep from leaving to atmosphere.

or you can use aero forces to pull yourself into a deeper-than-ballistic and get higher Gs.

Keep in mind you gotta suffer the Gs of changing your path though, so if you are going straight towards a planet at 2km/s you gotta do a turn at 2km/s, and thats gona leave a mark (or a fleshy puddle)

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Plus the fact earth itself moves on its course around the sun due to gravity means than a ship immune to gravity will have trouble tracking with the planet around the sun without applying constant thrust.

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Posted (edited)
44 minutes ago, RCgothic said:

Plus the fact earth itself moves on its course around the sun due to gravity means than a ship immune to gravity will have trouble tracking with the planet around the sun without applying constant thrust.

Hmmm... over long periods of time yes. But given that inertia has not been played with at all, it will take quite some time for that to make a difference, since a spaceship's heading will be already similar to the orbit of the planet it left. How else could it land upon it otherwise?

Also so long you turn the anti-gravity field on and offf judiciously everything should be fine.

Edited by Spacescifi
Fix

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Absurd Question merged with Absurd thread. 

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