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How To Safely Land Scifi Torchships On Any Inhabited World


Spacescifi

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This is something I thought was a show stopper but it really is'nt.

We can take for granted that in popular scifi the powerbanks/generators that spaceships use are energy dense, even on par with matter/antimatter annhilation.

They also compact. Which is a bonus that lends itself toward safe landings for heavy SSTOs.

Of course you will have to make something up or else deal with radiation exhaust... since with it landings won't be safe. But if you can fudge out the radiation aspect you're fine.

Anyway it dawned on me that if you have a compact high density power source on your starship that lets you perform like a torchship and do FTL hyperspace jumps... no way you want to land with it onboard... but neither do you have to.

Solution: Have several lower energy powerbank backups for landings. They have roughly just enough energy to deorbit, land, and reach orbit.... once.

Meanwhile you stash the rest of your compact powerbanks in an orbiting small shuttlecraft, which waits for the mothership to rendezvous with it in orbit later.

This thus solves the problem of trying to land a spaceship with doomsday energy levels... since you are stashing all of that in low planet orbit in a small shuttle instead.

So shuttlecraft are essential to spaceships with high energy compact powerbanks... since they are the perfect place to stash the explosive powerbanks when you want to land the mothership without the potential of wiping out a country.

Instead of that at worst if your ship blows up it will be like a Tsar bomb or close.

 

Which while still dangerous is a lot better than wiping out a whole country.

Edited by Spacescifi
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42 minutes ago, Spacescifi said:

This thus solves the problem of trying to land a spaceship with doomsday energy levels... since you are stashing all of that in low planet orbit in a small shuttle instead.

Actually, no. If you have sufficient energy to power any sci-fi ship's main engines, you're already sitting on doomsday levels of energy. If you know what the Kzinti lesson is, that would be great. All this mention of power banks is for naught. If you're concerned for their ability to explode then automatically, there will be a common knowledge of how to forcibly release that stored energy, and evildoers will be willing and able to do it.

51 minutes ago, Spacescifi said:

since they are the perfect place to stash the explosive powerbanks when you want to land the mothership without the potential of wiping out a country.

There are so many things wrong with this idea too... To put it simply, if a mothership needs to be gutted in order to land "safely" then it's not a mothership. At best it's actually a huge dumb payload and the same shuttles are its power source and main engines. And that leads back to my point above, about doomsday levels of energy.

You don't want to leave those "shuttles" alone in orbit anyway. Bad things can happen and they'll explode with all the might that you're trying to ignore... and then the "mothership" becomes a beached whale without anyone dying (assuming no one is going to be on those shuttles).

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56 minutes ago, JadeOfMaar said:

Actually, no. If you have sufficient energy to power any sci-fi ship's main engines, you're already sitting on doomsday levels of energy. If you know what the Kzinti lesson is, that would be great. All this mention of power banks is for naught. If you're concerned for their ability to explode then automatically, there will be a common knowledge of how to forcibly release that stored energy, and evildoers will be willing and able to do it.

There are so many things wrong with this idea too... To put it simply, if a mothership needs to be gutted in order to land "safely" then it's not a mothership. At best it's actually a huge dumb payload and the same shuttles are its power source and main engines. And that leads back to my point above, about doomsday levels of energy.

You don't want to leave those "shuttles" alone in orbit anyway. Bad things can happen and they'll explode with all the might that you're trying to ignore... and then the "mothership" becomes a beached whale without anyone dying (assuming no one is going to be on those shuttles).

 

When I say compact and high energy powerbank, I mean something literally small enough to carry (about the size of a baseball bat).

You can stash multiple powerbanks inside the ship's core generator, and remove them just as easily.

Gutting the ship as you call it is anything but. It is literally just stashing away a bundle of powerbanks crew can carry on a shuttle.

 

The engines are never removed but they need the powerbanks to function... so it is good the powerbanks are small and very energy dense.

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2 hours ago, sevenperforce said:

If you’re worried about overly-energetic thrust at landing, just inject extra inert propellant into the exhaust steam to increase thrust and decrease energy.

You don’t need a whole new thread for this solution. 

This post was not about overly energetic exhaust.... besides, doing what you suggest does nothing about the vast potential power in the ship's powerbanks, which if blown up would be catastrophic (especially given the scifi trope of FTL jumps being powered by spaceships).

 

My OP was an attempt to justify landing large SSTOs without them being so potentially deadly no that no one would.

Edited by Spacescifi
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18 hours ago, Spacescifi said:

This post was not about overly energetic exhaust.... besides, doing what you suggest does nothing about the vast potential power in the ship's powerbanks, which if blown up would be catastrophic (especially given the scifi trope of FTL jumps being powered by spaceships).

 

My OP was an attempt to justify landing large SSTOs without them being so potentially deadly no that no one would.

Like I said earlier. If you can pack the energy (moreover, into a tiny volume) to land any capable sci-fi ship, you are already carrying doomsday levels of energy. It's only a matter of if and how terrorists can make it explode. In any case, sci-fi ships generally have security systems such that no one can just break in and cause a meltdown.

 

I feel like half the time you're asking about SSTO propulsion, though. You should already have been informed on, and settled on something ages ago. Carrying around or riding in something that will cause mass destruction if it breaks in the right way is a very normal issue for sci-fi things. The threat thereof, generally only happens if you have people who can and deliberately want to cause that kind of destruction. It's a "Keep calm and live with it" kind of thing because the thing holding that kind of energy is usually built such that it's not going to be an issue 99% of the time.

 

On 3/19/2023 at 1:52 AM, Spacescifi said:

We can take for granted that in popular scifi the powerbanks/generators that spaceships use are energy dense, even on par with matter/antimatter annhilation.

They also compact.

On the other hand, I haven't watched enough of StarGate SG-1 or Babylon 5 but I know StarGate has "ZPM" things that are basically near-infinite energy stored in a battery in the form of a crystal that you hold like a key or wear like a necklace. I'm sure those don't explode if you destroy them. So in comes another very big issue I'd like to point out. Where do you draw the line between hard sci-fi and soft (sci-fantasy)? You need to have some standards for what physics and technology apply in your ideal sci-fi universe, then you won't have to post a bunch of threads asking "How can I make illogical condition #2498 work?" and you'd be able to decide for yourself "Ehhh. I don't like how these things in this sci-fi work, because actual reason A, B and E."

We look forward to questions like "I'm interested in SSTO propulsion tech X. What are its pros and cons? How can I reduce the cons or make them useful? What better tech can I use instead?" and it would be very helpful to us who come to answer you, if you made it clear if you're all in on hard sci-fi or if you want help spinning something realistic but extremely dangerous, to fit your established and well-defined sci-fi ruleset.

I know what engine tech I would use, whether hard sci-fi or in sci-fantasy with custom rules. I'd love to see you reach that place.

 

Please do some actual research, some worldbuilding, and define those standards.

Project Rho/"Atomic Rockets" is a library of concept tech and Isaac Arthur is a YouTube channel that talks about, and feeds the imagination with, lots of plausible and semi-plausible scenarios. Indulge yourself. Your audience will love you for it.

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1 hour ago, JadeOfMaar said:

Like I said earlier. If you can pack the energy (moreover, into a tiny volume) to land any capable sci-fi ship, you are already carrying doomsday levels of energy. It's only a matter of if and how terrorists can make it explode. In any case, sci-fi ships generally have security systems such that no one can just break in and cause a meltdown.

 

I feel like half the time you're asking about SSTO propulsion, though. You should already have been informed on, and settled on something ages ago. Carrying around or riding in something that will cause mass destruction if it breaks in the right way is a very normal issue for sci-fi things. The threat thereof, generally only happens if you have people who can and deliberately want to cause that kind of destruction. It's a "Keep calm and live with it" kind of thing because the thing holding that kind of energy is usually built such that it's not going to be an issue 99% of the time.

 

On the other hand, I haven't watched enough of StarGate SG-1 or Babylon 5 but I know StarGate has "ZPM" things that are basically near-infinite energy stored in a battery in the form of a crystal that you hold like a key or wear like a necklace. I'm sure those don't explode if you destroy them. So in comes another very big issue I'd like to point out. Where do you draw the line between hard sci-fi and soft (sci-fantasy)? You need to have some standards for what physics and technology apply in your ideal sci-fi universe, then you won't have to post a bunch of threads asking "How can I make illogical condition #2498 work?" and you'd be able to decide for yourself "Ehhh. I don't like how these things in this sci-fi work, because actual reason A, B and E."

We look forward to questions like "I'm interested in SSTO propulsion tech X. What are its pros and cons? How can I reduce the cons or make them useful? What better tech can I use instead?" and it would be very helpful to us who come to answer you, if you made it clear if you're all in on hard sci-fi or if you want help spinning something realistic but extremely dangerous, to fit your established and well-defined sci-fi ruleset.

I know what engine tech I would use, whether hard sci-fi or in sci-fantasy with custom rules. I'd love to see you reach that place.

 

Please do some actual research, some worldbuilding, and define those standards.

Project Rho/"Atomic Rockets" is a library of concept tech and Isaac Arthur is a YouTube channel that talks about, and feeds the imagination with, lots of plausible and semi-plausible scenarios. Indulge yourself. Your audience will love you for it.

 

By now I actually do know what kind of scifi drive wilI use (fictionally photon-like drive that trades the massive heat for pure repulsive force... thus it's heat is not an issue).

Drives may be fictional but I prefer that the energy required to pull off such feats to be more realistic. Thus the thread... and knowing that makes a difference in a given setting.

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On 3/19/2023 at 1:03 AM, Spacescifi said:

When I say compact and high energy powerbank, I mean something literally small enough to carry (about the size of a baseball bat).

I don't think you have proper appreciation for how high energy density works. I've built an electric bicycle recently, and when testing things out, had bad temporary connection from the battery to the motor. It wasn't even a short - just really bad contact coupled with inductance of a 750W motor creating a voltage spike and an arc that instantly turned about an inch of thick copper wire into white-hot molten spray leaving scorch marks on all it hit. The steel clamp I used to hold thing down had holes burned through it, but fortunately everything else suffered only superficial damage and no fires got started.

That wasn't the whole battery going up in flames. That was just a spark it caused. The whole battery packs a punch of nearly a pound of C4. Of course, it's not that impressive for a thing that's over 4kg in total, but then again, when I'm starting to compare a bicycle battery to a quantity of high explosives that you don't joke around with, that should start putting things into a perspective.

We've got desensitized to just how much of a boom can anything that's good energy storage cause. People worked really, really hard to first find and then improve on something as stable as gasoline and diesel. These things are absolutely shockingly stable for the energy they hold. So we're used to think of the energy storage for moving a car as nothing much, but this isn't at all normal.

Of course, we aren't talking about moving a car. We're talking about moving a starship. And here we are in a completely different class of energy densities. This isn't a nuclear energy, which is about a thousand times more energy-dense. We have to go a factor of a thousand on top of that. We're talking about means of energy generation where the mass defect comes with the territory. You have to convert a significant portion of the rest mass into energy. These things cannot be made safe. Nor compact. They have to have the mass to expend into the energy you are trying to harness. And really, we only know of two principles that can even work for this - we're talking about either black holes or matter-antimatter reaction. Neither of these can be safeguarded. Neither of these is going to be something you plug in as a battery.

As @JadeOfMaar correctly pointed out, any starship is a potential planet killer. And I'll add to it, that it doesn't at all need to land on the surface to be devastating. Having it go up in a blaze of gamma rays in orbit will still sterilize a third of the planet surface and make the rest uninhabitable for a very long time.

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Inspired by @K^2’s molten copper example, I thought it would be entertaining to look up a more extreme real-world example - the Large Hadron Collider beam dump system.

Aka, how do you safely absorb 350 MJ of energy packed into a few nanograms of protons travelling at relativistic speeds?

Like this.

“Each beam dump absorber consists of a 7m long segmented carbon cylinder of 700mm diameter, contained in a steel cylinder, comprising the dump core (TDE). This is water cooled, and surrounded by about 750 tonnes of concrete and iron shielding. The dump is housed in a dedicated cavern (UD) at the end of the transfer tunnels (TD).“

Edit.

Whilst 350 MJ is certainly a non-trivial amount of energy, it’s pretty small beer compared to the amounts of energy that get bandied around these threads.

As soon as antimatter annihilation enters the discussion you can basically (at least for a rough comparison) square that number and multiply by the mass of antimatter annihilated. Then double the result for good measure.

 

 

 

 

Edited by KSK
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1 hour ago, K^2 said:

We've got desensitized to just how much of a boom can anything that's good energy storage cause. People worked really, really hard to first find and then improve on something as stable as gasoline and diesel. These things are absolutely shockingly stable for the energy they hold.

This is also why very stable high explosives (detonated by shock waves) are used and low explosives (ignited by fire or electricity) are restricted to detonators to set off high explosives.  Stable high explosives can be burned safely and are crafted not to be a hazard unless a detonators is used.

The battery packs for electric cars are verging into being way too dangerous.  Something will need to be done about that.

 

1 hour ago, K^2 said:

Having [a starship explode] in a blaze of gamma rays in orbit will still sterilize a third of the planet surface and make the rest uninhabitable for a very long time.

Up to a certain size, the atmosphere should provide at least some protection.  And atmosphereless bodies should have buried facilities to protect from other radiation sources.  No one will want to test this.  And starships will always be dangerous and have to be under strict control.

Edited by Jacke
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3 hours ago, Jacke said:

Up to a certain size, the atmosphere will protect.

It's harder for me to make an estimate for a catastrophic failure of a black hole drive. On the net, it's safer, and an accidental failure is likely to release most of the energy in a pair of beams. But that would make intentional release more deadly, potentially, as you can direct the peak output at the planet. So there's a pretty wide range here. But the ballpark should still be like what we expect from a matter-antimatter explosion, which I can give estimates for.

The output will be a gamma burst with a peak somewhere in tens to hundreds of MeV. Dental X-Ray is under 100keV. Nuclear blast mostly peaks in a similar range, with some radiation into low MeV ranges. So we're talking harsh gamma radiation. Now, lets look at the intensity.

First, we need to know how big our ship is. Say we want to carry a crew of about 100. Now, I have no idea what the standards are going to be like for interstellar travel, but I think applying metrics for cruise ships should give us a ballpark. Typical occupancy factor is about 30kT per passenger, giving us a 3MT payload. Lets load it for a one way 10ly journey. Note that a 1g torch gives us a factor of a * 1ly / c of almost exactly 1. That means the half-way Lorentz boost factor is 1 + 1ly/yr2 * 5ly / c2 = 6. (Oh, yeah, torch ships be scraping that interstellar space. We're not even talking about how to mitigate that here.)

The relevant rocket equation for a light drive torch is v/c = tanh(ln m/m0). And, of course, tanh-1(v/c) = coth-1(gamma). Or in other words, ln(m/m0) = cosh-1(gamma)* This gives us m/m0 for our hypothetical starship of about 12. Of course, then we have to slow down, so we have to square this for a total of 144. Rounding that a bit, we're looking at 4.5GT or 4.5x1012 kg of matter-antimatter loaded up for this one way trip.

Lets say we parked this beauty about half way to the Moon. That's a 4*pi*(200,000km)2 sphere to which 4x1029J of energy will be spread. Each square meter of Earth's surface facing the ship will receive 8x1011 J of energy.

To put this into perspective, Earth's surface radiates about 500W of energy from every square meter under normal ambient temperature. It would take about 50 years for Earth to lose all that heat at 300K surface temperature. Of course, Earth's surface temperature would be nowhere near 300K following such an event.

So lets see how much effect an atmosphere of Earth would do against this. Lets say, the atmosphere absorbs most of that. There are about 10T of air above every square meter of the surface. It takes about 700J to heat up 1kg of air by 1K. So we're looking at an atmospheric temperature of well over 10,000K. That's hotter than the photosphere of the Sun and would give the entire atmosphere an average kinetic energy of the gas well above the escape velocity. That means, first, the surface would receive a massive burn from direct contact with a star twice as hot as our Sun, followed pretty much immediately by half of the atmosphere of the planet heading off for interplanetary space. Realistically, at 10MeV+ energies, a lot of direct gamma radiation would be getting through, but it hardly matters whether it's the superheated atmosphere or the gamma radiation that slags the surface.

To paraphrase a Simpson's character, "Ze atmosphere, it does nothing."

 

tl;dr: A detonation of a matter-antimatter photon drive torch designed for a one-way 10ly journey with a crew of 100 and parked half the way to the Moon would evaporate the atmosphere from the side of the Earth facing the explosion and slag the surface. What happens on the shadow side is left up to the imagination of the reader, but it's not good(tm).

The effects of the release of these quantities of energy are so devastating, I'd hesitate to allow any sort of a practical interstellar ship within the orbit of Jupiter.

 

 

* Since this is a useful equation for napkin estimates, given the topics that come up in this forum, in general, if you have a torch ship that needs to travel a distance X at acceleration a, the relativistic rocket equation is given by:

cosh((ve/c) ln(m2/m02)) = 1 + a (x/2) / c2

The squares on masses come from having to speed up and slow down. The thing that makes this so much easier to work with is that if you work with optimal light drive torch ship, a = 1ly/yr2, c = 1ly/yr, and ve/c = 1. So as long as you do x in light years, every other variable is 1 except for ln(m/m0) which is the thing you need to compute. You still need to compute hyperbolic trig functions here, but at least you don't have to look up a lot of obscure constants.

Edit: P.S. Because people probably aren't that familiar with hyperbolic trig functions, while you do want to pull out a calculator (or do a couple of series terms if you know 'em) for low factors, cosh(ln(z)) tends to 1 + z/2 for large z. Past 50ly or so, the above formula is really just (m/m0)2 = x for ve = c and a = 1ly/yr2. So you literally can do a torch-ship rocket equation estimate in your head by taking the distance you wish to travel and squaring it. Square it again for round trip.

And yes, this does heavily imply that while getting out of your own star system is really hard, once you can go past your few nearby stars, you can go just about anywhere

Edited by K^2
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9 hours ago, K^2 said:

It's harder for me to make an estimate for a catastrophic failure of a black hole drive. On the net, it's safer, and an accidental failure is likely to release most of the energy in a pair of beams. But that would make intentional release more deadly, potentially, as you can direct the peak output at the planet. So there's a pretty wide range here. But the ballpark should still be like what we expect from a matter-antimatter explosion, which I can give estimates for.

The output will be a gamma burst with a peak somewhere in tens to hundreds of MeV. Dental X-Ray is under 100keV. Nuclear blast mostly peaks in a similar range, with some radiation into low MeV ranges. So we're talking harsh gamma radiation. Now, lets look at the intensity.

First, we need to know how big our ship is. Say we want to carry a crew of about 100. Now, I have no idea what the standards are going to be like for interstellar travel, but I think applying metrics for cruise ships should give us a ballpark. Typical occupancy factor is about 30kT per passenger, giving us a 3MT payload. Lets load it for a one way 10ly journey. Note that a 1g torch gives us a factor of a * 1ly / c of almost exactly 1. That means the half-way Lorentz boost factor is 1 + 1ly/yr2 * 5ly / c2 = 6. (Oh, yeah, torch ships be scraping that interstellar space. We're not even talking about how to mitigate that here.)

The relevant rocket equation for a light drive torch is v/c = tanh(ln m/m0). And, of course, tanh-1(v/c) = coth-1(gamma). Or in other words, ln(m/m0) = cosh-1(gamma)* This gives us m/m0 for our hypothetical starship of about 12. Of course, then we have to slow down, so we have to square this for a total of 144. Rounding that a bit, we're looking at 4.5GT or 4.5x1012 kg of matter-antimatter loaded up for this one way trip.

Lets say we parked this beauty about half way to the Moon. That's a 4*pi*(200,000km)2 sphere to which 4x1029J of energy will be spread. Each square meter of Earth's surface facing the ship will receive 8x1011 J of energy.

To put this into perspective, Earth's surface radiates about 500W of energy from every square meter under normal ambient temperature. It would take about 50 years for Earth to lose all that heat at 300K surface temperature. Of course, Earth's surface temperature would be nowhere near 300K following such an event.

So lets see how much effect an atmosphere of Earth would do against this. Lets say, the atmosphere absorbs most of that. There are about 10T of air above every square meter of the surface. It takes about 700J to heat up 1kg of air by 1K. So we're looking at an atmospheric temperature of well over 10,000K. That's hotter than the photosphere of the Sun and would give the entire atmosphere an average kinetic energy of the gas well above the escape velocity. That means, first, the surface would receive a massive burn from direct contact with a star twice as hot as our Sun, followed pretty much immediately by half of the atmosphere of the planet heading off for interplanetary space. Realistically, at 10MeV+ energies, a lot of direct gamma radiation would be getting through, but it hardly matters whether it's the superheated atmosphere or the gamma radiation that slags the surface.

To paraphrase a Simpson's character, "Ze atmosphere, it does nothing."

 

tl;dr: A detonation of a matter-antimatter photon drive torch designed for a one-way 10ly journey with a crew of 100 and parked half the way to the Moon would evaporate the atmosphere from the side of the Earth facing the explosion and slag the surface. What happens on the shadow side is left up to the imagination of the reader, but it's not good(tm).

The effects of the release of these quantities of energy are so devastating, I'd hesitate to allow any sort of a practical interstellar ship within the orbit of Jupiter.

 

 

* Since this is a useful equation for napkin estimates, given the topics that come up in this forum, in general, if you have a torch ship that needs to travel a distance X at acceleration a, the relativistic rocket equation is given by:

cosh((ve/c) ln(m2/m02)) = 1 + a (x/2) / c2

The squares on masses come from having to speed up and slow down. The thing that makes this so much easier to work with is that if you work with optimal light drive torch ship, a = 1ly/yr2, c = 1ly/yr, and ve/c = 1. So as long as you do x in light years, every other variable is 1 except for ln(m/m0) which is the thing you need to compute. You still need to compute hyperbolic trig functions here, but at least you don't have to look up a lot of obscure constants.

Edit: P.S. Because people probably aren't that familiar with hyperbolic trig functions, while you do want to pull out a calculator (or do a couple of series terms if you know 'em) for low factors, cosh(ln(z)) tends to 1 + z/2 for large z. Past 50ly or so, the above formula is really just (m/m0)2 = x for ve = c and a = 1ly/yr2. So you literally can do a torch-ship rocket equation estimate in your head by taking the distance you wish to travel and squaring it. Square it again for round trip.

And yes, this does heavily imply that while getting out of your own star system is really hard, once you can go past your few nearby stars, you can go just about anywhere

This is a nobel mathematical effort and a well made point. Yet I had no intention of FTL energies being super high, nor for a torchship to literally fly out of a solar system and somehow survive all the tiny stuff hitting it as well as oort clouds around it and the next system over.

FTL jumps could involve a risky manuver that involves interacting with a star that provides the energy for you. Cloaking devices become necessary or otherwise a big asteroid as a shield in the short time before jumping so the ship would not burn up. Jumping from star to star essentially.

Infrasfructure already in place like stargates would be safer.

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9 hours ago, Spacescifi said:

Yet I had no intention of FTL energies being super high

That was for a sublight torch, and I'm making no accounting for shielding. Purely energies required to accelerate up to speed, then slow down again. We don't have a fully working model for a practical FTL ship, but what we have suggests that the requirements will be higher if it's at all possible. Likewise, wile a strong enough magnetic field should resolve a problem of shielding for the voyage, that will induce drag, which will also increase the amount of fuel needed. Though, it will also make stopping a little easier, so it might not be as extreme. I will leave working out the math of hyperrelativistic drag to someone with more spare time.

Nonetheless, this is a lower bound on the kind of energy you need for an interstellar ship of any kind, and it's a horrifying planet killing weapon in the wrong hands under the rosiest of estimates. Something a bit more realistic we might not want to let closer to Earth than the Oort cloud.

6 hours ago, kerbiloid said:

To be founded.

Yes, or I'd be a recipient for sure. :D

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