Astro Hacker News - NASA's DART spacecraft changed an asteroid's orbit around the sun

gatreddi |next [-]

Wild that we went from "can we even deflect an asteroid" to measurably changing a solar orbit. 150 milliseconds sounds tiny until you realize compounding over decades makes that a meaningful trajectory shift. The engineering confidence this gives for actual planetary defense is massive.

prism56 |next |previous [-]

Interesting. I'd not considered the loss of mass as a means of propulsion.

Obviously there was the kinetic energy transfer but the impact ejacted some of the asteroids mass opposite to it's trajectory further increasing it's trajectory change.

Cool demonstration, hopefully not needed one day.

messe |root |parent [-]

That's how rockets work.

prism56 |root |parent [-]

Yeah, I sort of meant in the context of an object losing its mass, it's seldom used on earth as the effects are small but on the timescale/distance/speeds of an asteroid it could have noticeable effects.

Rockets are using mass loss but there's more going on with the rapidly expanding gas causing the increased impulse.

fc417fc802 |root |parent [-]

Rockets are able to optimize due to dealing with a gas. It's still just pushing off of a disconnected mass. You go one way the lost mass goes the other.

If you think about it that's how a cannon works. The projectile gets pushed forwards and the barrel gets pushed in the opposite direction. Some of the larger ones can push their launcher back quite a bit more than you might expect.

My point is that this is actually a common failure of intuition. We tend to think of larger objects on earth as fixed and in our day to day life on dry land they often are (at least more or less) due to static friction.

A slightly more interesting observation (I think) is that if the bodies don't achieve escape velocity relative to one another then the forces all cancel out in the end. It just might take an arbitrarily long time in the case of similarly sized masses.

yubainu |next |previous [-]

That's interesting news. I wonder how much kinetic energy it had. This accumulation of information might be useful if an asteroid were to hit the Earth someday. At the very least, it's more realistic than sending oil drilling experts to an asteroid.

willis936 |root |parent [-]

>it's more realistic than sending oil drilling experts to an asteroid

Mandatory sharing of Ben Afleck commentary speaking for all of us.

https://youtu.be/-ahtp0sjA5U

NooneAtAll3 |next |previous [-]

I'm annoyed at these nothing-burger titles...

Instead of pointing out that exact measurements finally came in (of long term movement change), journalist instead focused on the obvious outcome that everyone expects and knows

wartywhoa23 |next |previous [-]

Well done, DART, which country did you aim it to?

zeusdclxvi |root |parent [-]

India

hulitu |next |previous [-]

> NASA's DART spacecraft changed an asteroid's orbit around the sun

Captain Obvious strikes again. Is school so low quality, that someone has to write a news article about it and somebody else thinks this is worth posting on a technical forum ?

fay_ |next |previous [-]

[dead]

p0w3n3d |previous [-]

Wow, that's the first step!

However, the most efficient method would be actually land (I know - maybe even impossible?) on it, and use propellers to change its trajectory. We don't have too much throwaway high-tech to crash it on asteroids...

XYen0n |root |parent |next [-]

Impact is actually a more efficient method, as it avoids the fuel consumption required for deceleration and soft landings.

Incipient |root |parent |previous [-]

I'm not sure this is actually a necessary explanation...but while propellers technically COULD function in space (not a perfect vacuum, right?)...they're basically going to be useless.

Rexxar |root |parent [-]

He probably misuses "propeller" which is strangely restrictive to "rotative blade propulsion" in English whereas "to propel" is generic in its meaning.

fc417fc802 |root |parent [-]

Be careful about how you store those inflammable propellers.