Scratch Earth-killer asteroid off your list of existential threats

Can do you a really strong vup of tea (Yorkshire of course) - would that help?

I am a firm believer in "Scientists have calculated that the chances of something so patently absurd actually existing are millions to one. But magicians have calculated that million-to-one chances crop up nine times out of ten.”

My reason for suggesting sentinels beyond the Asteroid belt id simply for a clearer view outward and sufficient warning to 'Do all those things we never had time for before........ kissing our arse goodbye.'(Or phoning Bruce Willis' successor.)

Volume should be measured in Olympic swimming pools and area in Waleses.

Mea culpa.

The surface area of a sphere centred on Sol and reaching to the asteroid belt is about 12,000,000,000,000 Welsh area units.

For London based readers it's about 150,000,000,000,000,000 times the surface area of Putney High Street.

Re: We need sentinels out past the asteroid belt looking for incoming.

You're missing a trick... we include a lot of fuel with each of the sentinels. Then when they spot something on a collision course they ram it - which should alter the orbit sufficiently for it to miss. And if it's caught far enough out it'll only need a fairly small tap to make the difference. Obviously we'll need a few spare sentinels to fill the gap afterwards.

<flame-trigger mode on>It won't be cheap, but probably cheaper than Brexit! </>

Re: We need sentinels out past the asteroid belt looking for incoming.

@Ugotta B. Kiddingme "However, even if we do put the requisite number of sentinels in the described area, that alone is insufficient. We must also develop the technology to eliminate or at least mitigate an incoming threat. "

I'd guess that the engineering difficulty and expense of filling interplanetary space with enough incoming rock sensors to give good coverage of the asteroid belt and beyond would be similar or greater than the difficulty and cost of developing the means to deal with a big incoming rock.

I've long thought that all we really need is detection systems which can give adequate warning time of a big incoming rock - "adequate" in this case meaning "long enough for those holding the purse strings to get the message and throw enough money at the problem soon enough to develop and send a mission to deal with it".

I mean, there are lots of ideas about how to deal with big incoming rocks. There is also, ooh, roughly 70 years of space engineering development under humanity's collective belt by now (a V2/A4 passed the Kármán line in 1944; the USA far exceeded that altitude in 1948) including space-going proper nuclear power reactors (the Soviets flew some), long-duration crewed missions, on-orbit repair and assembly experience, a large global aerospace production capacity, and reliable heavy-lift launchers.

The Yanks even worked on a nuclear reactor powered rocket (NERVA). The designs could be dusted off and developed into modern flight hardware - I'm thinking that getting to and shifting a big rock quickly would take nuclear propulsion.

Yes, normally, you'd not want to run the risk of blowing up a nuclear reactor when attempting to put it into space, but if the alternative is species extinction, minds might well change.

The job of dealing with a seriously threatening incoming rock doesn't seem impossible - just difficult and expensive and I reckon getting the funding to develop the required technology would need a clear and present danger.

The bigger the incoming rock, the longer warning we'd need - but then again, bigger rocks are easier to spot.

Whether or not we'd currently get long enough warning and quick enough funding is anyone's guess.

Re: n-body problem?

"Unless they get REALLY close together most of those rocks probably have negligible influence on one another."

For values of "really" that boil down to "collisions"