Ask Slashdot: Best Payloads For Asteroid Diverter/Killer Mission?

TheRealHocusLocus writes: The Emergency Asteroid Defence Project has launched a crowdfunded IndieGoGo campaign to help produce a set of working blueprints for a two-stage HAIV, or Hypervelocity Asteroid Intercept Vehicle. This HAIV paper (PDF) describes the use of a leading kinetic impactor to make a crater — a following nuclear warhead would detonate in the crater for maximum energy transfer. The plans would be available for philanthropists to bring to prototype stage, while your friendly local nuclear weapon state supplies the warhead. This may be a best-fit solution. But just ask Morgan Freeman: these strategies could fail. What — if any — backup strategy could be integrated into an HAIV mission as a fail-safe in case the primary fails? Here is a review of strategies (some fanciful, few deployable) if we have to divert an asteroid with very short lead time. A gentle landing on the object may not be feasible, and we must rely on things that push hard or go boom. For example: detonating nearby to ablate surface materials and create recoil in the direction we wish to nudge. Also, with multiple warheads and precise timing, would it be possible to create a "shaped" nuclear explosion in space?

Comments

Re:In defense of the human race

[JaredOfEuropa]

That is just too funny. In the same spirit, I suggest we send up Celine Dion and Justin Bieber on that asteroid buster mission. They won't be of any help when things go wrong, but if the primary mission succeeds, we will not only have won back out world, we will have made it a better place.

Moon rocks

[Anonymous Coward]

You need a moon base (not manned) to do this right. Then you throw moon rocks at the impending impactor. Doing it from a smaller gravity well means you can sling them into space more easily via something like a magnetic rail gun (yes, you need to put the moon rocks into a container made of iron / steel so it works with a mag solution).

Re:Moon rocks

[TheRealHocusLocus]

You need a moon base (not manned) to do this right. Then you throw moon rocks at the impending impactor. Doing it from a smaller gravity well means you can sling them into space more easily via something like a magnetic rail gun (yes, you need to put the moon rocks into a container made of iron / steel so it works with a mag solution).

+1 Insightful

A series of mass-produced kinetic impactors launched from the lunar surface by an EM rocket sled, each a ferrous metal cylinder containing lunar regolith with some propellent, attitude jets for course correction, (perhaps) a main engine for additional impact velocity. The probability of several or many reaching target is high. I give you a gold star. We could even retaliate against Mars.

It could be used to target Earth too, let's hope to be mature enough to resist. And hopefully its accuracy is better than Popeye's Pappy as he attempts a warning shot across the bow.

Re:Moon rocks

[dwywit]

"The moon is a harsh mistress" is a good reference for this.

Re:How would nukes exert force on an asteroid?

[Anonymous Coward]

The Orion project looked at how to push a large object with an explosion in a vacuum.
Project_Orion_(nuclear_propulsion)

ablation by laser

[bzipitidoo]

Beam enough laser light at the object to heat its surface to the point that it ablates. That will push it onto a different course. We won't even have to leave Earth for that to work. Of course, it does need an awful lot of laser power, but if our very survival is at stake, maybe we could do it. Here's the relevant XKCD what if.

Obviously

[rossdee]

Bruce Willis

Re:ask Slashdot

[TheRealHocusLocus]

Any chance that you might consider posting "Ask Slashdot" articles in the "Ask Slashdot" section in the future? Please?

I believe the proper forum for this question is "Ask Slashdot". Please re-post your question there.

Why not a type of Bola?

[Vonotar82]

How about shooting some tethers at it and deploying a counter-weight (rocket-powered?) to the object to swing it out of orbit? Make it into a Bola?

Re:tennis rackets

[TheRealHocusLocus]

one million tennis rackets.

A tennis racket of sunlight, as in a change of albedo on part of an object's surface using a light colored mesh, has been proposed for Apophis [2036]. Looks promising for known longer term threats which require small adjustment. From the paper Predicting the Earth encounters of (99942) Apophis [2007] p.13,

"altering the energy absorption and emission properties of a few hundred square meters of its surface (i.e., a 40 x 40 m patch) as late as 2018 could divert Apophis from impact in 2036; that is, the currently unknown distribution of thermal properties across Apophis can make the difference between an impact and a miss. Implementations of such a deïection might include depositing materials on Apophis' surface similar to the Kapton or carbon-ïber mesh sheets being considered for solar sails. With areal densities of 3 to 5 g m^-2 420 to 700 kg of carbon-ïber mesh could cover ~35-100% of the surface of Apophis in material with an emissivity of 0.4 to 0.9. For Kapton, static charge build-up in thematerial or asteroid due to solar UV exposure could aid deployment to the surface in such a low gravity environment. If an actionable hazard is found to exist, it would be necessary to move an object's entire uncertainty region (not just the nominal trajectory) away from the Earth. To provide margin adequate to cover all unknowns for Apophis, larger albedo modiïcations might be required. The modiïcation required will therefore depend on the predicted size of the trajectory uncertainty region in 2036 and thus on the asteroid's physical properties."

Re: Nuclear waste

[davester666]

To show Russia we mean business.

Solar sail with a modest angle to the sail

[Antique Geekmeister]

Solar sails are light payload, the forces involved are modest and cumulative rather than requiring a single controlled thrust under extreme circumstances, and need only modest anchorage or very modest netting to attach to the asteroid. They can provide continuous thrust for the lifespan of the sail, rather than a single high energy event, so they're much safer to build and to handle and much, much safer to test. Attached early enough, they should easily shift an asteroid or comet enough to avoid a crash. And properly constructed, they could be used to guide the object to almost any orbit desired, including guiding it to L4 or L5 to be a resource.

Assuming you are not just trolling.....

[robbak]

It is very difficult to 'shoot something into the sun'. You first need to get it out of the Earth's gravity, and then you need to decelerate it by 20 km/sec.

This is, frankly, impossible. You might be able to put a small payload to the sun if you used a very big rocket, and did a Venus fly-by. This way you could dispose of a few kilograms at a cost of a few hundred billion dollars.

Re:Assuming you are not just trolling.....

[Frobnicator]

It is very difficult to 'shoot something into the sun'. You first need to get it out of the Earth's gravity, and then you need to decelerate it by 20 km/sec. This is, frankly, impossible. You might be able to put a small payload to the sun if you used a very big rocket, and did a Venus fly-by. This way you could dispose of a few kilograms at a cost of a few hundred billion dollars.

ok i'll bite, not being physicist I am curious what decelerating something by 20km/sec has to do with shooting something to the sun.

Because we orbit the Sun.

It would actually take less fuel to launch it to a distant star than to hit the nearby Sun.

We are orbiting the Sun. Anything we launch out of our orbit is also going to continue in the same path, similarly orbiting the Sun, and because it is small, drift away from the Sun. That can be leveraged to hit another star with minimum fuel consumption, although the journey would be long. Think along the lines of the Voyager probes or various other launches to locations beyond the planet.

If you want to hit the Sun you need to change its velocity so it is no longer in orbit of our star (slowing it down relative to Sun), and also push it firmly toward the Sun strong enough that it goes in. The star is not like a drain hole sucking things in, stellar winds and constant ejections push things out. It is not enough to get it outside Earth's orbit with a rail gun or other accelerator. Aiming for the Sun requires an enormous amount of energy, more than any single accelerator has made in human history.

Re:Assuming you are not just trolling.....

[robbak]

Anything small that is (cosmically) near something big is in an orbit of that big object. Read that again. Then read on.

From here on, I will call the two things 'rock' and 'sun'.

We still call things going very fast as being in an orbit. We call these hyperbolic orbits, and this orbit carries the rock away from the sun after a single pass. These items have 'escape velocity'

Anything at less than escape velocity will be in a normal orbit. A normal orbit is not circular, it is an even, oval shape called an ellipse. The earth's orbit is nearly circular. We say that the earth's orbit has 'low eccentricity'. Its speed doesn't slow down or speed up much over its orbit. It stays at around 30 km/sec all year. A comet's orbit is highly eccentric. When it is far away from the sun, it moves very slowly. Then it falls toward the sun, gaining speed. But that little bit of movement it had caries it away from the sun, so it misses the sun. The sun's gravity pulls the comet around, flinging it back out where it came from. It slows down again as the sun's gravity pulls it back, until it slows down, turning, and falls back again.

So, let's examine your statement that "anything that approaches the orbit of any body in space , will be drawn in to that body by virtue of gravity, unless it has sufficient mass and momentum to maintain an orbit." There is something here that has created this understanding, the understanding that anything that is moving will be stopped by friction. Any movement soon stops. But what is there is space to make a rock stop moving? There is no air to slow it down, no carpet to rub against. Only if it happens to run into something else, and there is not much in space to run into.

Anything that approaches a body in space will be in an orbit.

There is also the understanding that small things stop easier than big things. But this is again tainted by the fact that your life has been lived on a planet, with air things have to push through and surfaces things have to rub against. Forget those things - there is neither in space - and small things keep going just as well as big things. The little thing has less momentum, but it also has less weight - the force of gravity on it - and the two things cancel out. In all orbital equations - as long as the 'rock' is much smaller than the 'star' - the mass of the rock cancels out, and is irrelevant. For our original premise - which was the idea of launching a payload of nuclear waste into the sun, by the way - the payload of waste and the earth follow the same equations - their wildly different masses are irrelevant.

What about when you throw a stone at your brother? That stone is an object near the earth. Surely it isn't in an orbit? Well - it is. It follows an elliptical path like anything else. It is like that comet, moving fairly slowly far away from (the center of) the earth, and it would continue in an orbit unless something - your brother, a window, the earth itself - gets in the way. If you could throw it at 8 or 9 kilometers per second (and if there wasn't any pesky air) it would remain in orbit, travelling right around the earth to hit you in the back of the head 90 minutes later.

So, what would we have to do to get a payload off the earth, and to the sun? First we would have to get it away from the earth, and that is not easy. But once it is away from the earth, it would still be orbiting the Sun. We would need to slow it down, almost to a stop - from 30km/sec down to zero. That is hard. Remember, there is no friction out there, no tyres on a road. You have to use a rocket engine pushing backwards, and it is just as hard to slow down in space as it is to speed up. The measurement of a space craft's ability to change speed is an important number, and is measured in meters per second - we call it the 'delta-V' of a spacecraft. The entire Saturn-V moon rocket had a delta-V of about 18 kilometers per second - without a payload. So magic a complete Saturn-V rocket away from earth, and it could get a tiny payload about tw

Re:How would nukes exert force on an asteroid?

[painandgreed]

In atmosphere, nukes produce blast because of high energy x-rays igniting atmosphere. This won't happen in space.

So how would letting off a nuke near or on an asteroid produce reaction and change the course of the asteroid?

Basically, the x-rays will ignite the surface of the asteroid instead. If the material in the asteroid is sub-optimal for this purpose, there have been designs of turning a nuclear bomb into a kinetic weapon that should work in this regard. Basically the bomb sits in an x-ray reflective shell, and when the bomb explodes, the x-rays bounce around the shell before the exploded bits of the bomb destroy it and exit an aperture. At the end of the aperture is a large, dense block of x-ray absorbing material. This material is vaporized by the x-rays and is all traveling in a similar direction as the x-rays were all going in that general direction. This plasma moving at relativistic speeds then slams into the target like a nuclear shot gun blast. IIRC, this design was built for using nuclear bombs against space ships and it was estimated that it could direct 95% of the energy of the bomb at the intended target.