http://www.flightglobal.com/articles/2007/08/03/215924/nasa-plans-armageddon-spacecraft-to-blast-asteroid.html

03/08/07

By Rob Coppinger, Flight International

NASA's Marshall Space Flight Center has designed a nuclear-warhead-carrying spacecraft, to be launched by the US agency's proposed 's Ares V cargo launch vehicle, to deflect an asteroid that could threaten all life on Earth.

The 8.9m (29ft)-long "Cradle" spacecraft would carry six 1,500kg (3,300lb) missile-like interceptor vehicles that would carry one 1.2MT B83 nuclear warhead each, with a total mass of 11,035kg.

Launched by an Ares V, the spacecraft would leave low-Earth orbit using a 45,359kg liquid-oxygen/liquid-hydrogen fuelled "kick stage".

The spacecraft's target near-Earth object (NEO) is the Apophis asteroid, which will pass by the Earth within the orbit of the Moon in April 2029.

For the study, however, its orbit was changed to bring it into a "dead-centre" collision course with Earth and its mass was assumed to be 1,000,000kg. The spacecraft's possible launch dates were 2020 and 2021.

By the 2020s NASA concluded that "the nuclear interceptor option can deflect NEOs of [100-500m diameter] two years before impact, and larger NEOs with at least five years warning".

The Cradle would have solar arrays, radiators, a light detection and ranging (lidar) instrument, a set of wide and narrow field of view (W/NFOV) cameras for guidance, a reaction control system and an avionics and communications package.

Each interceptor vehicle, with a terminal rendezvous package (TRP), would have a hydrazine-fuelled engine, a nitrogen tetroxide reaction control system and a lidar, and W/NFOV cameras for guidance.

The first vehicle/TRP could be launched, for a stand-off detonation near the NEO, 5h before the last interceptor's release, or the six TRPs could arrive at 1h intervals where the Cradle is 100h from intercept.

"The Hollywood scenario solution of shooting several intercontinental ballistic missiles at the incoming rock is fraught with danger. It probably would not be sufficient to prevent impact, raising the additional hazard of radioactive materials from the blast being introduced into the atmosphere," says the report.

A kinetic "bullet" version would use this interceptor design, but have an inert warhead instead of a nuclear one. In both cases the lidar would acquire the target NEO at 5,000km (3,100 miles) distance, with TRP closing velocities of up to 10,000m/s (1,968,503ft/min).

The Marshall study also has a solar collector option that has a very different vehicle design to the warhead and kinetic vehicles. The collector, which is more like an orbiter probe, would maintain station near the NEO and use a 100m-diameter inflatable parabolic collector membrane to focus sunlight into a "thruster" that directs that energy on to the NEO's surface. The heating of surface material evaporates it generating thrust and deflection.

But before the solar, nuclear or kinetic missile-carrying spacecraft is launched, NASA concludes that a precursor mission is needed and would send a 1,500kg observer spacecraft to the asteroid to determine its composition.

Knowing its composition would help the agency determine if a solar, kinetic or nuclear spacecraft would have to be sent.

NASA's proposed Ares I crew launch vehicle would loft the 23,316kg, 14m-long, observer stack, consisting of a liquid-oxygen/liquid-hydrogen-fuelled RL-10 B-2 engine-powered "trans-asteroid insertion stage", a second bi-propellant rendezvous stage, and the spacecraft, into LEO.

The observer spacecraft would be based on the probe built for NASA's 2005 Comet encounter Deep Impact mission, using some of its payload instruments.

For its instruments, which include a laser range finder and a radar, the observer's main power source would be a radioisotope thermal generator. It would also carry a Lander and a box launcher for seismic impactors and gravity fly-by projectiles.

The Lander would have a constant thrust motor to keep it in contact with the NEO's surface in the low-gravity environment and have three seismic sensors on the end of three long legs with surface penetrating spikes. The seismic sensors would detect the effect of the observer's impactors' arrival.

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http://www.theregister.co.uk/2007/08/06/nasa_nuke_bot_vs_doom_boulder/

By Lewis Page

Monday 6th August 2007

NASA plans to deal with killer comets or asteroids on collision courses with Earth are more advanced than many analysts had thought.

Flight International reported on Friday that the agency's Marshall Space Flight Centre has developed designs for an asteroid-buster spacecraft which could be launched using the future Ares V cargo rocket.

According to Flight, Marshall engineers based their design study around the 99942 Apophis asteroid, which rounds the Sun eccentrically, veering in and out between the orbits of Mercury and Mars.

Apophis is estimated to be perhaps 270 metres across and it will pass close to Earth in 2029, well inside the orbit of the Moon and closing in to the same sort of distance as geosynchronous satellites.

There was initially some concern following Apophis' discovery in 2004 that it might strike the Earth devastatingly in 2029 or 2036 - hence the name ("Apophis is the Egyptian god of evil and destruction who dwelled in eternal darkness," says NASA.) Further observations have refined the data and it is now known that the likelihood of a collision with Apophis in the foreseeable future is extremely small.

It seems that the human race is to be spared any devastating hammerblow from the heavens this time; but there is presumably a very small chance of a TV satellite or two being taken out by Apophis as it swings by. This could indicate that the mysterious forces of the cosmos have no beef with humanity; just with some kinds of broadcast content. Talk about your divine judgement. We'll have to wait and see.

For the purposes of their asteroid-defence plan, however, Flight says that NASA boffins assumed a bullseye hit on the Earth by Apophis and set its mass at 1,000 tonnes - though NASA says its estimate of Apophis' mass is 21 million tonnes. This would, says the space agency, give an impact equivalent to a 400 megaton atomic-bomb barrage.

Disappointingly for fans of Armageddon, the NASA asteroid-defence mission included no role for any eccentric oil-drilling experts, nor even any straight-arrow astronauts. The human race would rely on robots to sacrifice themselves for our survival. Initially, a recce probe would be sent out in order to make sure of a threat asteroid's composition and flightpath; then the main mission would follow, blasting off in 2020 or 2021 in the case of Apophis.

Rather than smashing any troublesome space rock to pieces, it seems the plan would be to give it a relatively gentle nudge while it was still far away, so that it missed the Earth cleanly. Of course, a 20 million tonne boulder would need a hefty nudge - and under the headline-grabbingest NASA plan this would be delivered by a volley of up to six nuclear missiles packing 1.2 megaton B83 warheads. These would detonate a hundred metres or so from the asteroid, and the heat of the explosions would cause part of it to vapourise and shove the remainder to one side.

There was also an alternative design for the boulder-buster mission, in which the shunting missiles would use only their own kinetic energy. There was a third, more groovy option in which a solar powerplant craft would fly alongside the menacing meteor and focus the sun's rays to boil off asteroidal material, which would have the effect of gradually easing it off the path of danger.

Apparently, the three different plans are each optimised for different types of asteroid. Once the composition of a dangerous space object was known, the design of the interceptor would be selected.

NASA reportedly assessed that the nuclear option could push 100 metre to 500 metre sized boulders safely off course given two years' warning, and larger ones with a five year heads-up. The Flight report is here.

There was no word on any plan by the satellite-TV industry to do anything about Apophis, given that NASA plans to ignore the possible threat to viewing schedules. Richard Branson of Virgin Media also owns a private spaceship startup, Virgin Galactic, though this has suffered setbacks lately, and of course the imminent selloff of Virgin Media could make the point irrelevant. Also, disappointingly for telly lovers, the troubled Spaceship Two isn't actually capable of getting even into Earth orbit - let alone mounting a nuclear barrage in deep space.

Thus far, anyway, there has been no announcement by the bearded biz kingpin of any plan to purchase nukes or mount a personal asteroid expedition.