Lamar Smith: When Does A Small Asteroid Become Dangerous?
Asteroid retrieval is costly and uninspiring, Lamar Smith Op-ed, The Hill
“The proposed asteroid retrieval mission would contribute very little to planetary defense efforts. The size of the target asteroid for this mission is only 7-10 meters in diameter, too small to cause any damage to Earth. Any insight gained by such a mission would have little relevance to protecting against larger “city-killer” asteroids. Congress directed NASA in 2005 to identify and track 90 percent of asteroids larger than 140 meters by 2020. Asteroids of this size are ones that could cause significant damage, and NASA still has work to do to accomplish this goal. Asteroids that are 7-10 meters simply disintegrate in our atmosphere.”
Russian Meteor’s Origin and Size Pinned Down, Space.com
“The asteroid was about 17 meters in diameter and weighed approximately 10,000 metric tons,” Peter Brown, a physics professor at the University of Western Ontario in Canada, said in a statement. “It struck Earth’s atmosphere at 40,000 mph and broke apart about 12 to 15 miles above Earth’s surface. The energy of the resulting explosion exceeded 470 kilotons of TNT.” That’s 30 to 40 times more powerful than the atomic bomb the United States dropped on the Japanese city of Hiroshima during World War II. The Russian fireball likely produced the most powerful such space rock blast since a 130-foot (40 m) object exploded over Siberia in 1908, flattening 825 square miles (2,137 square km) of forest.
Always good to hear a reasoned argument about space policy from a politician.
“The mission also would have little scientific value because the targeted asteroid would not be what is called a ‘carbonaceous chondrite.'”
This is an odd statement. Metallic asteroids are one of the less-studied types. And all the documents I have seen for this plan show a carbonaceous chondrite as the intended target. Any idea where Rep. Smith got this from?
Granted, it’s something I got second or third hand, but I gather the thinking in the minor bodies community is that metallic asteroids are scientifically uninteresting because they are basically just big lumps of metal. There’s just not a lot of mystery there, and what questions people have had can largely be answered by looking at metallic meteorites, without a need to do a lot of in-space evaluation.
Whether or not this is true is a different question, but the argument might be along these lines.
One possibility is that the metal asteroids have higher mass/density and therefore would be more tricky to work with, increasing the risks of injury, damage or faliure. A CC rock would be easier and safer, in theory, to work with first out, and would require less thrust (per unit volume) to start and stop moving. Just a guess on my part.
And better for mining.
He is correct that objects in the 7-10 meter range disintegrate in the atmosphere. He may be faulted for other things, but this is not one of them.
But then again, “disintegrate” can describe quite a variety of situations. If we started with a 7-meter asteroid that was mostly nickel-iron, not an uncommon object in theory, and it came through the atmosphere at an oblique angle approaching a right angle (i.e., minimum travel through the atmosphere), and let it be aimed at Mr. Smith’s backyard, I think he would be a little more concerned.
We can’t let ourselves be fooled by the idea that disintegrated automatically means breaking into ever-smaller pieces that completely disappear before reaching the ground, and that all rocks but the biggest will “disintegrate.” It’s not just rock size, but also rock composition, approach speed and approach angle that determine what kind of material and/or shock wave will hit the ground, and how much damage will result. Even ambient temperature and air pressure can affect the results. Even if no material hits the ground, the shock wave and the thermal energy generated are capable of doing significant damage.
And so as not to dismiss the possibility of wild coincidence, imagine if a small rock hit an airliner flying at 400 mph at a cruise altitude of 31,000 feet.
When we consider the size distribution of material orbiting in the solar system — more smaller rocks than large ones — then statistically we can expect more “visits” from smaller rocks, so we had better know for certain what we’re talking about when predicting their threat to us. Quite a few professional computer simulations have been done modeling asteroid impacts which suggest that even 7-10 meter rocks can do much damage and take lives.
Qualifier: most of what I’m saying is based on NOVA TV programs from PBS.
Not just simulations.
Small iron-nickel asteroids (or meteoroids) pose the most immediate danger. Such impacts as the Kaali impact in Estonia and the newly found Kamil impact crater, as well as several other (relatively) recent impacts, are thought to have been caused by iron-nickel objects less than 10 m avg. diameter. The objects were 1-2 m (Kamil) or 4-5 m (Kaali) when they hit the ground. The Kaali object did break up, but the result is that the event created at least 9 closely spaced impact craters of varying size. It probably caused a forest fire, and serious local destruction. If an impact of this magnitude hit a city, it could do serious damage and kill thousands.
There’s also the anomalous meteoroid which hit SE Peru in 2007. That was a small chondrite, which surprised most people exactly because it was the general impression that objects of that size and composotion would burn up completely or at least break up and slow down to terminal velocity.
On the other hand, if an object of that size and speed hit the ocean, there would be no detectable evidence – in fact, it’s possible that many such objects have hit the ocean in historical times, and some may even have hit land in unpopulated areas, which is most of the land of earth.
A possible example of this is the Wabar crater group, of a somewhat similar magnitude as the Kaali crater group, which may have occurred within the last few centuries. Fortunately it happened in one of the least populated areas of earth – the Saudi Arabian desert! this group has now been covered by sand.
http://www.passc.net/EarthI…
(Kaalijarv is the biggest impact crater in the Kaali group, but there are nine craters)
http://www.passc.net/EarthI…
http://www.passc.net/EarthI…
http://www.passc.net/EarthI…
“On the other hand, if an object of that size and speed hit the ocean, there would be no detectable evidence“
Not quite true, actually. The impact would cause a tidal wave in direct proportion to the amount of kinetic energy dissipated by the impact. The height of the wave above the waterline would in turn be in inverse proportion to the depth of the water at the point of impact, and changes as it moves through water of changing depths. This is why a wave that starts out as a tiny ripple can become a 50-foot city destroyer when it hits the shallow water on a beach. Most of the original kinetic energy is retained.
So, the impact energy may propagate inland, or it may actually create a crater on the ocean floor beneath the impact point, the latter being the ones that “disappear,” unless you look in the right spot. Both the kinetic energy and the angle of incidence would affect which situation would occur.
Tidal wave? No, it will not create a “tidal” wave if it hit the middle of the ocean. A large asteroid would create a tsunami, but an object a few metres across would not. Even the US nuclear tests (in the low KT range) created insignificant tsunami effects at fairly close range. At the much longer ranges and much greater depths I’m talking about it would have no significant effect.
Think it through. The kinetic energy of impact has to go somewhere — it can not simply disappear. A wave will be created by an impact, anywhere in the ocean that it hits. What I’m saying is that the size of that wave is determined by where it hits; and the amount of kinetic energy it possesses (which is determined by its mass and velocity); and the water depth beneath the wave as it moves away from the impact point. This can be seen whether you use the middle of the Pacific Ocean or a swimming pool.
Well, it will create a wave, but the energy will be dissipated before it reach any land, if such an object hit the ocean FAR from land. I was not referring to any near coast hit. Perhaps some hydrophones will hear it, if it happened today?
The point I was making is that through known history, a lot of such objects could have hit the oceans (far from land!) and we wouldn’t know about it. However, if one of those objects (relatively small iron objects in the 5-15 m range before it entered the atmosphere) hit a city, it could do a lot of damage. Obviously a larger iron asteroid would do more damage, but they are rarer. Does that justify the towing attempt by NASA? I don’t know. I suppose they have to start somewhere.
“The size of the target asteroid for this mission is only 7-10 meters in
diameter, too small to cause any damage to Earth.”
That is probably deliberate. For a training mission we want to ensure
that we do not cause any damage. Experience has shown that first attempts at anything almost always end in failure. By deliberately choosing a small asteroid we can guarantee the failure will not kill anyone.
Later missions can move dangerous asteroids using bigger spacecraft. We will know how to do it by then. Currently we just think we know how to do it.
Planetary defence is not a one off mission, it is a long term program. The program will continue after every member of the current Congress has retired.
“Any insight gained by such a mission would have little relevance to protecting against larger “city-killer” asteroids.” I don’t see why not. Obviously capturing a city-killer will be an order of magnitude harder. I learned to drive in a compact and now I drive an SUV – you have to start somewhere. Why were LEO missions flow before going to the Moon?
I think Lamar Smith has missed the point of exploration – you don’t go because you know what you are going to find or what you are going to get out of it, you go because you don’t know. “…little evidence that a current stated goal for NASA’s human spaceflight program…has been widely accepted as a compelling destination…” Perhaps that is because of the fractured debate on the issue? Frankly, it doesn’t matter what the next destination is, just get out and go!
If it’s only a few meters in diameter, why bring it back to lunar space rather than Earth orbit where manned missions to investigate it would be cheap and routine?
The cynic in me already knows the answer is SLS.
Perhaps for the experience of bringing something from outsystem back to a stable location at an L point, which may be common practice in the future if we’re acquiring and processing off-Earth resources. Putting something into a LEO is easy by comparison.
“calling the mission a detour from human exploration”
It can only be a “detour” if human exploration was going somewhere to begin with.
My agreement with Rep. Smith is that as a one-off mission it is not very valuable. (IMHO almost any one-off mission of any type isn’t very valuable)
If it was the US policy to “own NEOs”, that is to seriously map them out, visit lots of them to gain deep knowledge about them, figure out various techniques to adjust their orbits, and figure out how to exploit them as resources, then this would be a good first step.
I personally think a NEO campaign (not a single mission) would be good.
I agree, but also we need to consider that sometimes a single mission is necessary to learn just how viable/difficult a new mission type is. There’s no substitute for experience.
“Throughout its history, our space program has set goals that required innovation and technologies yet to be developed, and the results have been astonishing. ” “Congress directed NASA in 2005….”
A decade ago, Congress discarded the cheaper depot centric architecture. It mandated that 40 year old shuttle technology be retained with no possibility it would provide economic access to space, and specified 70 and 130 mT LVs be built, as well as super sized Apollo capsules. The yearly cost would be 2.5B/year–a budget profile that will stay constant for decades–even after development.
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“It is clear that the proposed asteroid retrieval mission would not require the development of a habitation module, a lander or other technologies that most agree will be necessary for expanding human presence into ‘deep space’.”
Okay, *delete* the asteroid mission. Same result: no money for a habitat, a lander (why is this needed?), nor other technologies needed to expand HSF.
So NASA and the admin today has been handed a big, fat lemon by the 2005 Congress and the 2010 Authorization Act: 4 new engine development programs and a capsule that can spend up to 25 days BLEO. Inspirational?
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“Landing on the Moon would develop technical capabilities for landing on and launching from a large celestial body, something NASA has not done for more than four decades”
Worse, congress thinks that landing on planets develops technical capabilities,what about ‘deep space’?
Oh no! the ability to land heavy objects on *Mars* with an atmosphere has nothing to do with the moon!
The lunar gravity is 1/6th g, mars, 1/3 g, but the long trip is micro-g.
How does this address bone loss issues?
The lunar surface blocks half the GCR, so L2 (or an asteroid location) is a better place to research GCR uncertainties and mitigation strategies.
A closed loop ECLSS system can be checked out in LEO or L2—why
spend all the energy sending it to the lunar surface?
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“SLS and Orion crew vehicle as the highest priorities for carrying out the Mars goal”
Could it get any worse?
Yep. Plans are to send a 20 mT earth ascent/return Orion capsule to Mars without the additional 20 mT of water to allow a male to stay in deep space for less than 300 days (currently its 360 days round trip).
The good news: if one just does *not* send Orion to
Mars, then NASA just gained 20 mT for the water around the habitat.
So what is the reason to retain Orion, when a lighter crew ascent /return capsule can be powered down at say L2 and not head to Mars?
With a LEO depot, zero boil-off LH2 the most economical for the tax payer, NASA can save billions using smaller LVs, so SLS is not required. Highest priority is SLS/Orion?!
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“Yet when it comes to the Obama administration’s latest asteroid mission proposal, it has not been able to adequately justify the rationale or budget for such a mission.“
So when given a lemon by Congress: (25 day capsule, a 130 mT
LV, with no budget for anything else) the admin tried to make lemonaid by
simply sending the capsule to an asteroid for a 4 hour spacewalk, trying to
change the aptly named “rocket to nowhere.”
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“While the exact mission cost is still unknown, experts have
estimated it could be as much as $2.6 billion. This is a hefty price tag at a
time when NASA can barely maintain its current mission priorities. “
What happened to total mission costs including development? But with a decade, oops really 4 decades, of HLV and 13 more years before the 4 hour spacewalk, is this not about $40B-50B (2.5B*20), not 2.6B? Not a great bargain, but slightly better than $40-50B to go nowhere, no?
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“NASA is in the business of making the impossible possible. “
Yup. This ‘roid is too small. Perhaps NASA should to return the moon back
to its location as of about 4.5B years ago and skip deep space exploration? Is SLS big enough?
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With a focus back to technology development which includes economic
access to space and GCR radiation protection, spinoffs to earth would be in the near term. Many more science and HSF missions would be possible, fit withing the budget, would be for the benefit of all, and most certainly would be inspirational.
Well said.
This Op-Ed is so chock full of technical inaccuracies it is a bit maddening. Almost every paragraph is flat wrong or grossly distorted. All this just makes me think that ARM must be on to something, since all Smith can do is attempt to take it apart, while ignoring the simple fact that he can’t fund his preferred option of returning to the moon let alone provide a compelling argument for doing so. The money simply isn’t there, not unless NASA wants to wait until the 2030’s to do it. Smith clearly doesn’t care about NASA actually doing anything so long as the money keeps flowing to his campaign sponsors.
I can think of one reason to look at bigger rocks, more a future technology issue than science — there’s been comments about metal and CC asteroids, but the bigger the rock is, the more likely it is to be a conglomerate — metal and stone and whatever all mixed randomly — which is going to be harder to work with because the center of gravity will not coincide with the physical center of the rock, and it’s most likely going to be tumbling in three dimensions, which is going to be tricky to stop.
Also, in the case of a possible Earth hit, a conglomerate is more likely to shatter in an unpredictable manner than be neatly deflected. Even the laser deflection scheme that’s been proposed would have this problem. This is probably not something to deal with first time out, but it’s part of the problem and can’t be ignored.
Once a conglomerate asteroid gets large enough we’re going to have the equivalent of mascons showing up, making even staying in stable orbit around it harder.
I would say that before we go after our first big one we’d better have figured out multiple techniques for dealing with stopping, steering, tumbling, etc., because I think it’s likely going to be a lot harder to handle than we think.
My first comment is, in terms the congressman can understand, is that he doesn’t know squat. As someone already commented, NASA’s intent is to target a ‘carbonaceous chondrite. Also, proving this technology leads to the potential to scale it up, and tackle larger and more hazardous rocks. Also this technology will be pathfinders for business interests. And from a plain curiosity and scientific interest, we have not seen any small asteroids close up. If the congressman had any instinct for engineering, he would recognize that the 10 meter is a good analog to understanding and manipulating 20 or 30 m rocks which are hazardous.