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.

Comments

Piggy ride!

[Chicken_Kickers]

Why can't we send a probe that will land on this asteroid and then piggy ride on it. That way we don't need more fuel to carry it round the solar system. If the asteroid doesn't go where we want, then have a relaunch mechanism for the probe to get off at the most suitable point in the asteroid's orbit.

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:Piggy ride!

[CrimsonAvenger]

Why can't we send a probe that will land on this asteroid and then piggy ride on it. That way we don't need more fuel to carry it round the solar system. If the asteroid doesn't go where we want, then have a relaunch mechanism for the probe to get off at the most suitable point in the asteroid's orbit.

If we have the deltaV to land on the rock, then we have the deltaV to match its orbit without bothering to land on it. So why waste time with the landing?

Or were you thinking that little or no deltaV would be required because the rock was passing close by?

Well, no, a quick guesstimate based on the limited information in the article has it passing at about 9km/s relative to Earth, at 64000km altitude. Which is rather more than escape speed. About 8500 m/s over Earth escape speed, in fact. We've sent probes out faster than that a few times. The stuff that goes out past Jupiter, for instance. But it's a non-trivial exercise.

Re:Piggy ride!

[MichaelSmith]

IF you land on it, it will continue to travel without fuel for propulsion for a VERY long time... that could be rather useful

It you match speeds with it you will continue to travel without fuel for propulsion indefinitely. Being docked to a rock will make no difference. The advantage of having the rock there is that you can mine it for resources and use it as a radiation shield. You could also push transfer momentum to it if you want to change your velocity.

Re:Piggy ride!

[meringuoid]

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

Physics doesn't work that way.

You seem to think it's like hopping on the back of an old London bus: grab it as it passes and jump up onto the step. But speeds in space are far greater than that. If you try to catch an asteroid as it passes, words like 'splat' or 'crunch' are appropriate. You need to match the asteroid's velocity very closely in order to land on it without being destroyed - and if you can do that, then you're on the same orbit as the asteroid anyway, and you'll go where it goes whether you land or not. So you don't actually need the asteroid to be there.

I suppose you might arrange something cunning with a big net and a lot of bungee rope, if you can pull off an incredibly accurate flight plan, but even so it's unlikely that the asteroid is going to be near any other targets of interest in the near future; it's more worth your while to load up the extra fuel needed to fly direct to the planet or moon you want to study.

Re:Piggy ride!

[MurphyZero]

If you could match speeds with it, you could go where it goes without need for the asteroid. Since the asteroid has no propulsion of its own, it's not providing any benefits, if you 'match' speeds (actually velocity, speed and direction). The benefit only comes in matching position and letting the asteroid change the velocity of the spacecraft to match. As long as the spacecraft survives that impact, then it can be used to provide a great momentum transfer.

Re:Piggy ride!

[pcolaman]

I vote we shoot it down, just to see if we can do it. That would be more fun, anyways. I nominate myself to push the button.

Re:Piggy ride!

[meringuoid]

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?

Yeah. No friction or air resistance in space, that's what you're missing. Oh, and all of physics since Galileo, you're missing that too.

The brick has less mass than the iron lump, true - and so it has proportionately less inertia. But the gravitational force on the brick is also less than that of the iron lump, by the same proportion. The two cancel out. If they have the same velocity, then if one escapes, so does the other. It's the same principle as how a brick will fall at the same speed as a feather, if dropped in a vacuum.

Similarly, if a spaceprobe and an asteroid fly away from the Earth at the same velocity, it doesn't matter whether they're attached or separate: both will follow the same path.

Re:Piggy ride!

[CrimsonAvenger]

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?

Have you read anything by this guy Newton? Fig, or Isaac, one of the two. He pretty much explained (about 300 years ago) how this whole "gravity" thing works.

And, for what's it's worth, 5 miles/second (I shudder to think you might have meant metres/second) is below escape velocity. It's barely above orbital velocity. So not even your lump of iron would escape. Even if gravity worked they way you think it does, as opposed to the way it really does.

Impossible in this timespan

[RabidMoose]

(IANARS) There's simply no way that any space agency could prepare and launch a probe with less than three days notice, and likely no good way to pre-build one without knowing what size/speed asteroid we might be lucky enough to launch at.

Re:Impossible in this timespan

[PolygamousRanchKid]

(IANARS) There's simply no way that any space agency could prepare and launch a probe with less than three days notice, and likely no good way to pre-build one without knowing what size/speed asteroid we might be lucky enough to launch at.

I dunno . . . The Thunderbirds seem to be able to get anywhere they want to go, real fast. And Doctor Who just seems to be able to go where ever he damn well pleases, as well.

Re:Impossible in this timespan

[Hurricane78]

Unfortunately though, they also have the disadvantage of not being real.

Which is quite unfortunate, in reality.

Re:Impossible in this timespan

[Nyeerrmm]

While you're absolutely correct, there is a program known as Operationally Responsive Space (ORS) thats being headed up by DoD rather than NASA that is headed in that direction. I think the time-frame they're considering is closer to 2 weeks, but the general idea is to be able to recognize a need, and design, construct and launch a mission in that period of time. That includes getting adjustable plug-and-play parts (GNC, Power, structures, propulsion) that you can tune and modify quickly to fit the mission profile.

Presumably, a lot of the work to streamline the process of designing the bus and plugging in instruments could be easily translated to space science missions, and if a future opportunity like this were available we could do exactly that. Of course, you'd have to have a pretty interesting guidance system and a very robust structure, since you'd only get an advantage if you stuck the probe in the asteroids path and let it slam into it to get the momentum.

Re:Impossible in this timespan

[Puffy Director Pants]

Dude, if you can make a functional space craft that looks like an English Police box, I'll support your candidacy for head of Nasa.

Re:Impossible in this timespan

[Dr.M0rph3us]

From TFA:

"This little cosmic surprise, designated 2009 DD45, turned up two days ago as a 19th-magnitude blip in images taken by Rob McNaught at Siding Spring Observatory in Australia. It was already within 1.5 million miles of Earth and closing fast."

So no, they had no prior info about this asteroid. And yes, this fact concerns me as well, but this is the problem with asteroids / comets having a low albedo - they're difficult to observe with the usual instruments.

Buzz vs. Non-buzz

[DynaSoar]

Three days notice. 20 to 50 meter diameter. Assume it's dense rock and a vertical impact trajectory into the ocean (avg. 1000 m depth).

Impact energy 116 kT to 1.8 MT. Very near the lowest energy potential impact of the known NEOs, actually. Not relevant here since the object quite clearly misses. But if and when one doesn't miss, someplace is going to catch a small to medium nuke sized blast, and there won't be time to do squat about it.

My money says we'll have the capability to defend ourselves against such an impact. The second time.

Re:Buzz vs. Non-buzz

[narcberry]

There's only so much matter, after enough time, we don't have to worry about anymore collisions.

I vote we wait it out.

Re:Another perspective

[MartinSchou]

1 km/s is EXACTLY 3,600 km/h. Not roughly 30,000 km/h as you suggest.

Parent links to malicious site

[Anonymous Coward]

Sturly is a redirection service similar to tinyurl. Luckily it provides a preview. The link wants to send you to the same "dragonslair" link that appeared in the 3D game without polygons story from earlier today.

Looking at the source of the page, it attempts to download a movie on eDonkey, change your AIM name, send off spam emails, open up lots more windows, and probably much more. It also moves the window around so you can't close it, and pops up messages when you try to alt+f4.

In short; DO NOT CLICK THE LINK.

Armageddon

[Samah]

Quick, someone notify Bruce Willis!

Close call

[mc1138]

While right now 64,000 puts it fairly far out in terms of all the junk orbiting the earth, it is significantly closer than the moon is. Even if it still missed the earth, just a few thousand kilometers closer and it could reek havoc on all the man-made junk spinning around the Earth. How much potential damage/debris could that cause?

Re:Fourth

[Anonymous Coward]

^That this was modded interesting made me lose faith in humanity.

Another one from Klendathu...

[allcoolnameswheretak]

Their aim is getting better. They will hit us eventually if we don't do something about those Bugs, soon.

So, I used a calc on the impact

[Ralph Spoilsport]

the calculator can be found here:
http://www.lpl.arizona.edu/impacteffects/

And the results are (assumed that you are 2000km from impact - if it hit it would be in the ocean...)

Your Inputs: Distance from Impact: 2000.00 km = 1242.00 miles
Projectile Diameter: 30.00 m = 98.40 ft = 0.02 miles
Projectile Density: 8000 kg/m3
Impact Velocity: 17.00 km/s = 10.56 miles/s
Impact Angle: 90 degrees
Target Density: 1000 kg/m3
Target Type: Liquid Water of depth 100.00
meters, over typical rock.

Energy: Energy before atmospheric entry: 1.63 x 1016 Joules = 3.90 MegaTons TNT
The average interval between impacts of this size somewhere on Earth is 314.0 years

Atmospheric Entry: The projectile begins to breakup at an altitude of 14100 meters = 46100 ft
The projectile reaches the ground in a broken condition. The mass of projectile strikes the surface at velocity 10.8 km/s = 6.7 miles/s The impact energy is 6.58 x 1015 Joules = 1.57 MegaTons.
The broken projectile fragments strike the ground in an ellipse of dimension 0.151 km by 0.151 km

Major Global Changes: The Earth is not strongly disturbed by the impact and loses negligible mass.
The impact does not make a noticeable change in the Earth's rotation period or the tilt of its axis.
The impact does not shift the Earth's orbit noticeably.

Crater Dimensions:
What does this mean?

The crater opened in the water has a diameter of 1.4 km = 0.866 miles
For the crater formed in the seafloor: Crater shape is normal in spite of atmospheric crushing; fragments are not significantly dispersed.
Transient Crater Diameter: 670 m = 2200 ft
Transient Crater Depth: 237 m = 777 ft
Final Crater Diameter: 837 m = 2750 ft
Final Crater Depth: 179 m = 586 ft

The crater formed is a simple crater
The floor of the crater is underlain by a lens of broken rock debris (breccia) with a maximum thickness of 82.8 m = 272 ft.
At this impact velocity ( Thermal Radiation: What does this mean?

At this impact velocity ( Seismic Effects: What does this mean?

The major seismic shaking will arrive at approximately 400 seconds.
Richter Scale Magnitude: 4.4
Mercalli Scale Intensity at a distance of 2000 km:
Nothing would be felt. However, seismic equipment may still detect the shaking.