[Maxwell Smart] Missed it by that much [/MS]
A couple of points, I believe that they’ve found some problems with centrifugal force being used as a substitute for gravity,apparently it affects the inner ear and a persons balance .
Whether this is an insurmountable problem I dont know.
Would there be any way to reverse Venus’s runaway greenhouse effect and terraform it given enough time?
I think a better scenario (for the need of a generation ship) would be the knowledge that the Sun is going to go nova, anything else just does not justify the building of such ship, Mars seems the better option in the Moon-Sized Object doomsday scenario.
I think the better way to go at it would be NOT hiding the truth, but telling it to everyone, getting the full thrust of all mankind into it, use up the whole fricking world’s Gross Product, some seemly impossible things could be done that way.
Man, do you even HAVE a Netflix account? We drill. Both shuttles will take off Tuesday at 6:30pm. Now, 67 minutes later, we dock with the Russian Space Station to meet cosmonaut Andropov, who will refuel the shuttles with liquid O2 - that’s your fuel - then we’ll release and take a 60 hour trip toward the moon. Now we only have one shot of landing on this rock, and that’s precisely when the asteroid passes by the moon. we’ll then use lunar gravity and burn our thrusters, slingshotting us around the moon, coming up behind the asteroid. We’ll be upward of 11 G’s. That’s part 1. Courtesy of Armageddon.
Then…we take our burrowing driller-train made of unobtainium and we hotwire the nukes, as one does. We see them through the core at a location that has to be accurate to the inch. We detonate them in a sequence that has to be accurate to the millisecond. And we outrun the biggest nuclear shockwave in history.
As anyone who has seen The Core would know.
Think people! I know the Straight Dope Science Advisory Board, we were at MIT together. And, in a situation like this, you-you really don’t wanna take the advice from a group who got a C minus in fake-astrophysics. The Straight Dope Advisors are… wrong. I’m right.
-kjckjc
Coriolis force, which is what makes you dizzy on a fast spinning ride, is proportional to the spin rate (rpms). So to make your spin rate slow enough you have to make your spnning habitat large enough. For 1G and a spin rate of only 1 rpm, you need a diameter of a little over a mile.
Although the OP specifies that we know there’s an oxygen atmosphere planet out there, if we can only get to it. If you had extreme doubts about being able to maintain artificial habitats forever, and the transportation problem was the lesser of two evils, it might be worth it. For that matter, even a nova might be survivable in the outer Kuiper belt, so that doesn’t change matters.
Even if you got rid of the greenhouse effect tomorrow, “Enough time” would be measured in millions of years. Venus is HOT. It’s close to the sun, even without the greenhouse, it would still have an atmosphere (presumably, since we want to live there), which helps insulate the planet. It would take a long, long time for that heat to radiate away into space.
I think that’s the problem with a generation ship. It would be relatively easy enough to build a space colony that was miles and miles and miles in diameter and just sit back and watch the earth be destroyed, but there’s a limit to how big a generation ship can be, and still be able to hold enough fuel to get to another solar system in any reasonable amount of time. I don’t know what that size limit is though. Maybe someone else does. But, I don’t think a generation ship can be large enough to approximate a Noah’s Ark people would want to live on for a few centuries, while carrying enough fuel to actually propel the darn thing.
The object is indeed the size of the moon and approaching for something around a perpendicular intersect. The reason for those two stipulations is to create an annihilation level event that can’t be avoided with current technologies. A: It’s too big to be deflected by any means we could use to get to it that would give us time to deflect a smaller object. B: It’s big enough to shatter the Earth upon impact. C: The approach vector makes any intercept impractical. If we have or develop a propulsion system that could get anything besides a probe to it, the solar system would be ours. If you feel that a moon sized object impacting the Earth wouldn’t be sufficient to destroy it, feel free to scale it up to whatever size will accomplish that goal.
If you really want to try for an intervention, I’d suggest moving our own moon into a polar orbit to act as a blockade. Sure, that’s going to be hell on the environment, and the impact will surely pelt us with several extinction level meteors in a very short time. But considering the alternative, it deserves having the numbers run on it.
I thought about starting a sister thread in GD about whether it would be better in this scenario to inform the entire population or keep it secret and come up with ficticious cover stories to justify the research projects. For this thread I’m subscribing to the opinion that while individually, people are intelligent, collectively they would be the pitchfork and torch brigade. May do that yet if someone doesn’t beat me to it.
GD thread opened here.
Would we have a better chance if the general public knew the truth.
Please confine this line of discussion to the linked thread.
The PTBs are hesitant to make a full disclosure because that bell definately can’t be un-rung and they want to be damned sure before they do.
Okay, but what you have to realize is that the problem of a ‘generation ship’ capable of reaching other star systems is orders of magnitude greater than the problem of deflecting even an entire planet. The energy requirements would enormous either way.
So if you’re going to say that deflecting it is impossible, I’d have to say an interstellar generation ship is impossible too. So we’re left with trying to survive elsewhere in our solar system.
I’m going to require numbers to back up that assertion. Yes the energy requirements for interstellar travel are daunting, but unless you’re talking about constant-1G accelleration to >99% lightspeed, it is not on the scale of moving planets.
Not to speak for Sam, but I think when he said, “the problem of a ‘generation ship’ capable of reaching other star systems is orders of magnitude greater than the problem of deflecting even an entire planet,” he meant the gestalt of technological problems that would need to be solved, not merely the energy requirements. Deflecting a planetary body is little more than an upscaling of currently-available technology–it’s just the energy and production requirements which are daunting. OTOH, successfully getting a generation ship to a distant star would necessitate technologies we don’t even have yet, most of which have been mentioned in this thread already. I would not say it’s unreasonable to suggest the latter is orders of magnitude more difficult than the former for that reason.
Does this moon have any resources? If it has any large amounts of radio active materials and water it could be possible to construct giant nuclear rockets at it’s rotational pole. The water would be super heated and ejected into space. Since it’s on the pole then the moon’s spin wouldn’t make day side acceleration cancel out night side acceleration.
I’m not saying that it would be impossible to alter the speed or trajectory of that large a body if you had the structures in place to do it. I’m saying that by the time you could travel there and get set up it would be too late to make a difference. The OP calls for effectively a right-angle intercept to maximize the difficulty of that solution.
How many years will it take to prepare something that can alter the momentum of that much mass? How many more years will it take to transport it there with available propulsion systems? The longer it takes to get a solution in place, the more deviation will be needed to effect a miss.
All of which really deviates from the question of the OP. Could we be prepared to launch a generation ship in 50 years if it were the only possibility of humanity’s continued existance? How would we outfit it to maximize the chances of success? What are the biggest technological obstacles?
I posted a cite earlier. You can calculate how much starting mass you need if you’re using a rocket. For even exotic rockets, the amount of energy required is amazing. Robert Forward calculated that a manned solar sail (not a generation ship, mind you - a very small manned probe) would require a laser so large its power output would be over 100 times the total power output of the entire planet.
There is one possibility - perhaps we’ll learn how to extract propulsion out of space itself. If we don’t need to throw away mass to move forward, the entire game changes. There’s still much we don’t know about dark energy and dark matter, and for that matter about the structure of the universe at the smallest scales. It’s not out of the real of possibility that we could figure out a way to extract energy or create a propulsive force.
But then, if we could do that, we could probably deflect the moon headed for us.
Wsn’t there an old movie about this thing? Trying to remember the name of it.
When Worlds Collide.
At what speed? You yourself pointed out the exponential increase in energy/reaction mass needed as you go faster. And in the example you cited they were talking about a total velocity change of 20% lightspeed- up to 10% and back down again. That’s hugely more difficult than a 2% velocity change- up to 1% and back down again. Which is why I pointed out that a huge but slow generation or hibernation ship might actually be easier than a small but fast ship.
And on checking, the figures you cite seem extraordinarily pessimistic. A gross weight to payload ratio of a million to one? The source I checked presumed an exhaust velocity of 3% lightspeed, which for a 20% velocity change gives a ratio of 400 to one.
Is it too much a hijack to ask: If a habitat was built on the moon, what would the effects of a moon size impactor hitting the Earth on the moon habitat? Catastropic moon quakes from the Texas size chunks of impactor & Earth hitting the moon? Would building on the dark side protect from direct impacts or would ejacta curve around to impact the dark side? Would the nuclear waste dumps ignite sending the moon out into the deeps of intersellar space?