Small Asteroid To Buzz Earth

ddelmonte writes in to tell us about a small near-earth object, discovered just 2 days ago, that is expected to pass within 64,000 km of our planet on March 2, 13:44 UT. NEO 2009 DD45 will be well inside the Moon's orbit and just under twice the altitude of geosynchronous satellites. According to Sky and Telescope, 2009 DD45's closest approach will be over the Pacific west of Tahiti, so observers in Australia, Japan, and perhaps Hawaii will have the best chance of spotting it with, say, an 8-in. telescope. Here's where you can generate an ephemeris of the object for your location. At closest approach NEO 2009 DD45 will be moving half a degree per minute and peaking around magnitude 10.5. It will be brighter than 13th magnitude for only a few hours.

Re:Piggy ride!

[Anonymous Coward]

You don't save any fuel by being near an asteroid. Putting the probe in the same orbit as the asteroid would have essentially the same fuel cost (actually a little less, because you would not have to overcome the escape velocity of the asteroid).

Re:Piggy ride!

[evanbd]

Having the asteroid there doesn't change anything, really. It costs the same amount of delta-v to put a probe on that orbit whether or not there's an asteroid (at least for tiny rocks like this; it would have to be getting toward small moon size to matter much). You already don't need propellant to carry a probe around the system -- things in space just coast, following an orbit determined by gravity. The hard part is getting it onto the right trajectory, not keeping it there.

Re:Piggy ride!

[amorsen]

Why can't we send a probe that will land on this asteroid and then piggy ride on it.

"Landing" would either actually be "crashing at a speed measured in km/s" or would require just as much fuel as going in the same orbit without the asteroid, and then what's the point...

Re:Another perspective

[wjh31]

about Zero when integrated over enough orbits, but for this encounter, while the speed wont change by then end of the encounter, but the velocity will, i think

Re:Another perspective

[Overzeetop]

m2/m1xdelta-v, or diminishingly small; that's the useful part about using planetary passes to change velocity - they affect the planet in a negligible way. Kind of like driving to the store makes a negligible change in the CO2 in the atmosphere vs. walking. If all the asteroids started going for a joy ride, or taking vacation past earth every summer just for the fun of it, we'd start to notice. ;-)

Re:Piggy ride!

[MrMista_B]

Well...

Landing a probe on an asteroid passing by at this speed, would be like trying to catch a bullet with your bare hands.

I'd say the mental imagery is pretty close to accurate, in both cases.

Re:Piggy ride!

[Meumeu]

Surely the asteroid has considerable inertia due to its mass? A probe would have to apply thrust to overcome gravity wells that it encounters. The asteroid will be affected by the "drag" of passing close to large bodies but already has considerable ineria.

Let's say that I sent a ping pong ball, a house brick, and a 20t lump of iron heading away from earth at 5 m/s. I would expect the ping pong ball to slow most quickly, followed by the house brick. In some situations, the lump of iron might be able to escape where the others would not. You'd experience the same effect if you tried to stop a car rolling down hill a ten miles per hour and then compared it to stopping a skate board moving at the same speed. Perhaps I'm missing something?

Yes, you're missing the basics of physics... This whole post is pretty much bullshit.

Re:Close call

[Nyeerrmm]

Without any actual analysis, I'll go out on a limb and estimate it would cause as much havoc as any large man-made piece of junk out there, like say a dead Soviet satellite. A much larger asteroid would be a different story, since not only would it have a larger footprint, but would also have hard-to-predict gravitational effects on all the satellites that got too near it. Of course, we're doing a pretty good job of detecting larger NEOs now... Apophis is the most problematic, mostly because we simply don't have high enough precision knowledge of its position to know where it will be in 2029 and 2036.

Re:Buzz vs. Non-buzz

[Frequency Domain]

We won't do anything about these things till there's a loss of life. There's a 70% chance it hits the ocean, and with 1MT energy? There's pretty good odds it will go unnoticed by anything but defence satellites.

You think sea strikes are harmless? The odds of actually hitting a city are pretty small, but the odds of hitting a chunk of water near enough to populated areas to cause tsunami damage are much larger since, according to NOAA [noaa.gov], coastal counties in the continental US account for only 17% of land area but have 53% of the population. Imagine what a 10m or more surge from a tsunami could do to the Netherlands, or Miami, or New York. For comparison purposes, the Sumatra tsunami of 2004 was estimated to release around 20MT of energy at the surface, and produced as much as 30m surges hundreds of miles away from the epicenter.

Re:Piggy ride!

[MichaelSmith]

Gigantic. Bungee.

This is actually not completely insane.

It is an insanely exciting idea. Imagine hooking on to an object like that in a small spacecraft. A few thoughts on the subject:

• Build an unmanned probe with can outfit a small asteroid with docking hardware. It could attach itself with two loops of rugged cable. Attached too the cable would be a socket which tethers can attach themselves to. A single installation could be used for decades by different spacecraft.
• Catch the asteroid with your tether extended. Consider the asteroid moving along +Z at 10km/s. Tether is 1000km long and the spacecraft is 1000km away from the point of capture along +X. Immdiately before capture explosives on the tether end assembly fire to accelerate the end of the tether. Magnetic and electric fields in the tether and socket may assist in a fast capture. Doing it this way eliminates sudden loads as the tether takes up slack. Instead the spacecraft is swung around (yeah at high G) and releases when it is headed in the right direction.
• Equip vehicles with heat shields and solar sails. Both require only present day technology. Aerobraking at (say) Venus could be used for a course change.
• Consider using angular momentum from Asteroids and free space tethers to store energy. One vehicle could sump energy into an object, another could make use of it.