Quote from: Eric Hedman on 02/15/2013 06:08 pmLet the hearings begin!http://thehill.com/blogs/blog-briefing-room/news/283427-house-committee-to-hold-hearing-on-asteroids-that-pose-a-potential-threat-to-earthAh! More funding for SLS! And hopefully an agency wide raise. Good.
Let the hearings begin!http://thehill.com/blogs/blog-briefing-room/news/283427-house-committee-to-hold-hearing-on-asteroids-that-pose-a-potential-threat-to-earth
... looking at the collection of seismograms...
I guess it will be an interesting case study in the future. Explosion of 500 kt at altitude 30 km above a large city.
Quote from: Robotbeat on 02/15/2013 09:35 pmThere's also never (during the space age) been such a pertinent, documented case of why it is important, and probably has never been such public attention to the topic, either.Gazing into the crystal ball, I can see Congress throwing some more money at the search effort. When we did our NEO study a few years ago the committee generally believed that the amount of money spent on doing the surveys should be increased a bit. Because NASA was then spending $4.5 million on the subject, "a bit" could be increasing it to $10 million annually.But here's some of the issues:-in order to substantially improve the surveys for these objects you have to spend A LOT more money. Essentially, you have to build a space-based telescope. No matter what B612 says, that's a half billion dollar investment.-compare the costs, and the risks, to other events that kill lots of people. If you go back only one decade I bet that you can easily determine that over 800,000 people worldwide were killed by seismic events (250,000 in Haiti alone). Earthquakes represent real dangers to human life.-where should that $500+ million be spent for maximum effect? Should it be spent on things like asteroids, which are very rare, or should it be spent on things that are much more common?But I'd hate to see a knee-jerk political reaction to throw cash at this without carefully balancing the issues.
There's also never (during the space age) been such a pertinent, documented case of why it is important, and probably has never been such public attention to the topic, either.
Quote from: ChileVerde on 02/16/2013 12:19 am... looking at the collection of seismograms...Is there any chance to tell from heliplot if we are looking at shock wave hitting the ground or at impact of massive solid body? (Theoretically, there should be difference in shape/magnitude, but I have no personal experience here). Or, in other words - could you tell by heliplot data that there was a large (on a tonne scale) body hitting the ground with supersonic speed? Or, do these plots give evidence that there was NO such event?
Quote from: FinalFrontier on 02/16/2013 10:47 amQuote from: Eric Hedman on 02/15/2013 06:08 pmLet the hearings begin!http://thehill.com/blogs/blog-briefing-room/news/283427-house-committee-to-hold-hearing-on-asteroids-that-pose-a-potential-threat-to-earthAh! More funding for SLS! And hopefully an agency wide raise. Good. No, the hearing is just public discovery/disclosure (and the other things that come with hearings). It might extend the visibility of the event, but increased federal funding is far from a certainty, especially on a large scale.
If the cost is $500M, it would seem reasonable considering that NASA has a $17B per year budget. This is the kind of work that NASA is expected to do. If NASA doesn't do this kind of work, taxpayers will eventually question whether their $17B per year "investment" into NASA is put to good use.
Quote from: yg1968 on 02/16/2013 12:23 pmIf the cost is $500M, it would seem reasonable considering that NASA has a $17B per year budget. This is the kind of work that NASA is expected to do. If NASA doesn't do this kind of work, taxpayers will eventually question whether their $17B per year "investment" into NASA is put to good use. Here is what has happened in the past:A few members of Congress (Rohrabacher is one) have inserted language into NASA authorization bills (not appropriations bills) requiring the agency to detect potentially hazardous NEOs. Because of the way that Congress works, where the leadership often has to give out trinkets to the members in order to get things passed, this language has survived into authorization acts even though the vast majority of members don't care about the subject or even know anything about it. (Note: this happens all the time for lots and lots of things, not just searching for asteroids.)This requirement landed on NASA, but did not come with any new money appropriated for that purpose. Now what the authorizing committee hoped would happen is that the administration (White House/President) would submit a budget proposal that included sufficient money to accomplish the task. But the administrations (Clinton, then Bush, then Obama) didn't care about the issue. So they did not ask for additional money to do it, they simply redirected money from inside NASA to do it partway. The result is that the money has gotten cut out of other things at NASA, and the agency has never really had the resources to accomplish it.This is just a variation of the common situation of the "unfunded mandate."What people within NASA have worried about for years is that Congress would increase the unfunded mandate, essentially directing that more of the agency's current budget be allocated for doing this thing. That would force them to cut the money from something else. But what? It's common for the advocates to say "take it from the science budget because asteroids are science." But counting rocks is not a scientific pursuit. And this is a terrestrial defense project, so why should that money come out of the science budget? Shouldn't the Department of Homeland Security or the DoD pay for it? And officially the administration has set a goal of sending humans to an asteroid, and so shouldn't the human spaceflight program spend the money searching for asteroids?
Quote from: Antares on 02/16/2013 12:43 amI think we'd need more data to increase confidence that the rocks came from the same meteor source.Klendathu?
I think we'd need more data to increase confidence that the rocks came from the same meteor source.
Anyone who knows russian. What are they saying in this video with regards to the impact crater?
Quote from: Blackstar on 02/16/2013 12:22 am-compare the costs, and the risks, to other events that kill lots of people. ... Earthquakes represent real dangers to human life.-where should that $500+ million be spent for maximum effect? Should it be spent on things like asteroids, which are very rare, or should it be spent on things that are much more common?Well, yes, but the question of what 0.5 $G buys in either case arises. I.e., suppose that amount of money buys a pretty complete assessment of asteroid risk that can be followed up with more $$ on prevention/ mitigation.You then have to figure out how the same amount of money can be spent on earthquake risk assessment and prevention/mitigation.In the case of earthquakes, we probably aren't going to prevent them any time soon, so does the 0.5 $G go into earthquake resistant construction in Haiti, Iran and other quaky places? And how much of the population gets protected for that amount of money?
-compare the costs, and the risks, to other events that kill lots of people. ... Earthquakes represent real dangers to human life.-where should that $500+ million be spent for maximum effect? Should it be spent on things like asteroids, which are very rare, or should it be spent on things that are much more common?
And yet, we don't do it [space programs in general] JUST because of an actuarial cost-benefit analysis. Very little of what NASA does would qualify, maybe some of the stuff in aeronautics.And again, there is an existential aspect of it that isn't captured in an actuarial perspective and it's one that doesn't really apply to earthquake prediction, etc.How much have we spent on Hubble? And Hubble doesn't really have an existential purpose. Half a billion for studying NEOs (and other targets, for sure) isn't unreasonable. Which isn't to say we /shouldn't/ be studying how to predict earthquakes, etc. Your arguments seem to work just as well against any kind of space project.
Quote from: QuantumG on 02/16/2013 02:56 amQuote from: Nittany Lion on 02/16/2013 02:43 amAn economist would say you equate marginal-utility-to-price ratios over all your purchases. A non-economist would say you maximize the bang for your bucks.Governmental spending should be allocated similarly and probably is.What's the weather like on your planet?... Snarky comments aside, our government works quite nicely on the whole. As evidence I’ll cite that one of our greatest problems is the number of people who want to come here, greatly in excess of what our immigration laws allow.
Quote from: Nittany Lion on 02/16/2013 02:43 amAn economist would say you equate marginal-utility-to-price ratios over all your purchases. A non-economist would say you maximize the bang for your bucks.Governmental spending should be allocated similarly and probably is.What's the weather like on your planet?
An economist would say you equate marginal-utility-to-price ratios over all your purchases. A non-economist would say you maximize the bang for your bucks.Governmental spending should be allocated similarly and probably is.
Air has density of about 10^-3, at ground level decreasing approximately exponentially with scale height, and the scale height is of order 10 km. Therefore meteors tend to break up at 10-20 km altitude if they don’t make it to the ground. A 1 m rock needs to sweep a path of over 2 km through the air to stop effectively, a 12 m rock needs about 24 km of air to stop. So a rock that big coming straight down will likely hit the ground.The Chelyabinsk meteor came in at a shallow angle, and so traversed a column of air long enough to brake it and break it. This is very fortunate, or we’d have had a ground detonation of a few hundred kilotons and likely mass casualties.Most of the injuries seem to have been from broken glass, consistent with reports of other large explosions.Glass breaks from overpressure of about 1/4 PSI – and as the bomb damage calculator (below) shows, that overpressure goes out to about 20 km radius (for ground detonations which this was not). Here we had an air detonation (worse) but with the energy spread out over a linear track, not deposited instantaneously at a point (both better and worse).Hence the damage was consistent along the track and for tens of km either side of it, but nowhere was there a point or line of extreme destruction. A little bit higher energy impact, steeper impact angle, faster speed or bigger rock, and there would have been a zone of severe damage surrounded by an elongated annulus of the moderate damage actually seen, and there would have been many deaths.
What if this thing had not been in an Earth-grazing trajectory, but had instead hit full-on, in surface-normal trajectory? Would it have smashed into the ground rather than exploding overhead?