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Getting towards the end of Apollo Mission - The Inside Story ...mention is made of the horrific N1 rocket explosion in the USSR in 1969.
Apparently, parts of the rocket landed 10 kms away from the launch site while a whole fuel tank landed 7 kms away. The blast wave from the rocket explosion was more like something from a nuclear explosion as far as those sheltering in the trenches were concerned.
Got me thinking about those artist renderings showing Starships standing close to the first City on Mars...
I was always sceptical about that and assumed any habitats would have to be at least 1-2kms away...but reading about the N1 explosion made me wonder whether we would really need a safety zone extending for 10kms? Of course, guess it might depend on the local topography. But what do you think would be a safe limit?
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Well, Louis, you are quite right to worry. Too many have not, when drawing up these illustrations.
The N1 and the Saturn-5 were more-or-less comparable in terms of explosive yield and damage potential. Witnesses to the Saturn launches at Cape Kennedy were within the impact zone for thrown debris at a mile or three. The saving grace was only that there would only be a few large pieces that would carry that far (the little stuff decelerates by drag and falls closer).
Being hit by one is a low probability simply because there aren't very many big pieces. The distance was adequate for a shock wave (not survivable) to decay to a subsonic blast wave (survivable). A subsonic blast wave is merely a subsonic wind. But these strong winds do a lot of damage on Earth in the form of tornadoes!
On Mars, there is only 0.7% the air density as on Earth. That really weakens the shock wave (there is zero shock wave in true vacuum, even from a nuclear explosion). My guess (ONLY a guess!) is that a mile or so is enough to make sure the thing has decayed to a survivable subsonic blast wave. And that subsonic wind will have a far lower force to it, because of the very low density.
On Mars, the debris problem is worse. There aren't very many big pieces, but there are a lot of little pieces flung from the site of the explosion. At 0.7% density, there isn't much air to slow the little ones down, so they will carry out very far from the blast. In other words, on Mars you will see a lot more shrapnel. A bloody lot more! You're probability of being hit by it a mile or three away is very much higher, much closer to a certainty.
I rather doubt ANYONE has yet thought this through! Musk is not the only one proposing to land rockets quite close to other rockets, or to other structures. All who propose such are VERY, VERY WRONG to do so! Because, sooner or later, one of those things is going to crash and explode.
Whether a "hard shell" or an inflatable, what is a shower of shrapnel going to do to an inhabited space? Depressurize it within seconds. Fatally to anyone inside. "Hard shell" is a relative term. ~0.010 inch aluminum will not stop a really hard-thrown rock by human hands, much less metal bits moving hundreds, or even thousands, of feet per second.
I'd say at least 2.5 miles (4 km). Maybe further.
GW
GW Johnson
McGregor, Texas
"There is nothing as expensive as a dead crew, especially one dead from a bad management decision"
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Thanks GW - great to have your expert advice on that.
I imagine large pieces of sharp-edged shrapnel moving at speed (supersonic speed?) could represent a real threat.
I think we should take your 4 km limit as the benchmark unless someone can argue persuasively for more or less.
It also argues for substantial regolith cover for habs (at least 1.5 metres) to be the standard - this will protect against not just radiation but also meteorites and rocket explosion debris.
I agree as well that we have to look at how close Starships are parked together. Certainly the human-passenger Starships must be at a remove from the cargo Starships and if there are two HP Starships they shouldn't be close together either. Of course a just-landed Starship is far less dangerous than a fully refuelled Starship.
Well, Louis, you are quite right to worry. Too many have not, when drawing up these illustrations.
The N1 and the Saturn-5 were more-or-less comparable in terms of explosive yield and damage potential. Witnesses to the Saturn launches at Cape Kennedy were within the impact zone for thrown debris at a mile or three. The saving grace was only that there would only be a few large pieces that would carry that far (the little stuff decelerates by drag and falls closer).
Being hit by one is a low probability simply because there aren't very many big pieces. The distance was adequate for a shock wave (not survivable) to decay to a subsonic blast wave (survivable). A subsonic blast wave is merely a subsonic wind. But these strong winds do a lot of damage on Earth in the form of tornadoes!
On Mars, there is only 0.7% the air density as on Earth. That really weakens the shock wave (there is zero shock wave in true vacuum, even from a nuclear explosion). My guess (ONLY a guess!) is that a mile or so is enough to make sure the thing has decayed to a survivable subsonic blast wave. And that subsonic wind will have a far lower force to it, because of the very low density.
On Mars, the debris problem is worse. There aren't very many big pieces, but there are a lot of little pieces flung from the site of the explosion. At 0.7% density, there isn't much air to slow the little ones down, so they will carry out very far from the blast. In other words, on Mars you will see a lot more shrapnel. A bloody lot more! You're probability of being hit by it a mile or three away is very much higher, much closer to a certainty.
I rather doubt ANYONE has yet thought this through! Musk is not the only one proposing to land rockets quite close to other rockets, or to other structures. All who propose such are VERY, VERY WRONG to do so! Because, sooner or later, one of those things is going to crash and explode.
Whether a "hard shell" or an inflatable, what is a shower of shrapnel going to do to an inhabited space? Depressurize it within seconds. Fatally to anyone inside. "Hard shell" is a relative term. ~0.010 inch aluminum will not stop a really hard-thrown rock by human hands, much less metal bits moving hundreds, or even thousands, of feet per second.
I'd say at least 2.5 miles (4 km). Maybe further.
GW
Let's Go to Mars...Google on: Fast Track to Mars blogspot.com
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