Larry Niven near-light-speed story - spaceship on course to hit the Earth. Would like to know more about it.

I am always concerned with the energy of rocket flight because it seems most space enthusiasts underestimate the needs for various space propulsion systems.

I once considered travelling at 1/4 light-speed since that seems about the maximum that could be reached without too exotic means. It is also the speed needed for travelling to Alfa Centauri and back within a human life time.

The Lorentz factor for this speed gives only 3.3 % deviation from non-relativistic mechanics so its influence is minor. But the energy needed to reach it is already enormous.

Some imagine a community of 10,000 people and therefore a huge spaceship would be needed to make such a long trip successful. But I considered the absolute minimum of a single interstellar traveler with a standard body weight of 75 kg. It turns out that at 1/4 light-speed his kinetic energy is even slightly more than the energy released in the largest human created energetic event : the TSAR BOMBA !

That was the 50 Megaton hydrogen bomb which the Soviet Union exploded in 1962. When his body would be put overboard and hit the Earth a similar explosion would result !

It seems Larry Niven also realized the enormous energy involved at near light-speed and years ago I read he wrote a story about it but I never found it. So anybody knows more, a title would be nice ?

  • That's a great amount of detail, I'm sure it'll get answered soon enough – Edlothiad Aug 8 '17 at 11:35
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    There are lots of Niven stories which address velocity/energy concerns. Any more detail on the actual story may help. – Broklynite Aug 8 '17 at 15:27
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    So the first and the last paragraph constitute your question, while everything in between are your own musings? Perhaps you should condense and clarify a bit. – SQB Aug 8 '17 at 16:29
  • That's not a Niven story I've ever read. – Swordblaster Aug 10 '17 at 5:19
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    @MartinGoldsack see my answer from August 2017 below. – Organic Marble Oct 23 '18 at 22:35

Your question reminds me of Niven's novel "World of Ptavvs". Disastrous effects due to collision of a NAFAL ship and inhabited planets is a theme in the early part of the book.

If he had hit Awtprun at more than nine-tenths light, he could have killed upwards of a million people. That was assuming he hit an ocean! The shock wave would knock every flying thing out of the air for a thousand miles around and scour the land clean, sink islands, tear down buildings half around the world.

(page 9)

I am not aware of any short Niven works on this theme - although I may not have read all the Draco Tavern stories.

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    I'll second this as the likely answer. The protagonist (at this point) is in a crippled spaceship who's super-luminal drive no longer works - he could have purchased a spare but instead decided on a deluxe padded command seat. He does have a status device, so he decides to point his ship at the nearest settled planet at sublight speeds and wait it out. He then realizes this will kill millions, so he aims at an agricultural planet. then he realizes this will cause financial damage, so he finally aims at the moon of a planet near an argicultural planet. That was Pluto, formerly around Neptune. – Maury Markowitz Aug 8 '17 at 20:15
  • @MauryMarkowitz Doesn't Niven call it a stasis device? – user14111 Aug 8 '17 at 20:23
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    Indeed, but my spell checker doesn't. – Maury Markowitz Aug 8 '17 at 22:51

Is it possible that you're instead thinking of "Sound Decision" by Robert Silverberg and Randall Garrett, described as the answer to Old SF story about the need to destroy an out-of-control passenger ship with a nuke before it crashes?? It involves a ship approaching Earth at high speed, a passenger liner in this case, and unable to decelerate or change course, and it's made clear that impact would kill millions.

"But its actual impact with Earth’s surface isn't going to be the thing that will do the damage. It won’t matter whether it comes down in Long Island Sound or in Times Square—it’s the impact with the atmosphere that will cause about twenty million deaths.”

No one said anything. The five men in the screen looked at him in blank-faced horror.

"You know what happens when a jet plane goes over a city too low?" Stanley said. "A supersonic jet can break windows. What sort of sound wave do you think a five-hundred-metric-ton spaceship will cause at—seventy-two thousand miles an hour?

"I’ll tell you. It would flatten every structure for miles around. If that ship hits Long Island Sound, New York City will be toppling in ruins before it ever arrives! Every town on Long Island is going to be pancaked. From Newark, New Jersey, to Hartford, Connecticut, that shock wave will knock over everything standing. This isn’t a matter of a few people in a ship dying; it's a matter of millions!”

It's not Niven, but it matches the plot you describe.

  • It matches if you consider 72,000 mph to be "near-light-speed". – user14111 Aug 8 '17 at 19:49
  • ^_^ Only off by a factor of a few thousand... and at such huge numbers, the mind just boggles. Honestly, I originally read the speed as being much higher. – FuzzyBoots Aug 8 '17 at 19:57

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