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12 Comments
Martin wrote:
From the article:
"Schweickart said that the report has just been delivered to one of the action teams for the U.N. Committee on the Peaceful Uses of Outer Space, starting the ball rolling for consideration of the panel's recommendations. "Nothing happens in the United Nations without a very structured procedure, and nothing happens fast," he said."
That sounds like a good reason for NOT involving the UN. I think that there ought not to be a procedure in place for dealing with asteroid impacts. Such an occurence would be a (up to now) singular event for humanity - it ought to be treated as such. Procedures delude people into thinking that everything is under control, when it isn't.
Schweickart is a crank. He's pushing the idea of using a "gravity tractor" to pull asteroids around, an idea which is a load of crap. Especially if you are dealing with a potential impactor.
Anonymous wrote:
Schweickart is a crank. He's pushing the idea of using a "gravity tractor" to pull asteroids around, an idea which is a load of crap. Especially if you are dealing with a potential impactor.
The "cranks" over at JPL don't seem to think so:
"Summary Statement by B612 Foundation regarding its contract with JPL
to conduct a detailed performance analysis of a transponder equipped
Gravity Tractor spacecraft."
A successful NEO deflection campaign will involve several key functional elements, including the ability to, in situ, precisely determine the orbit of a threatening NEO prior to and post deflection, and to precisely adjust the NEO’s orbit to assure its successful passage between return keyholes at the time of its closest approach to Earth. B612’s contract with
JPL called on it to quantify these two critical capabilities.
The analysis verified the viability of the transponder-Gravity Tractor (t-GT) spacecraft to perform these critical deflection functions. A full report of this work is now available on the B612 website at http://www.b612foundation.org/press/press.html, #18.
In summary a 140 meter diameter equivalent, Hayabusa-shaped NEO, with a rotation period of 6 hours was approached by the t-GT spacecraft with the initial task of determining a precise orbit for the NEO. Effective convergence in the orbit determination was reached after approximately 8 days of tracking and resulted in about a 5 meter (one sigma) error ellipse projected forward 18 years in time. A second orbit determination was performed following a simulated kinetic impact deflection during which the t-GT functioned as a standoff observer. The post-deflection orbit determination converged to the pre-deflection precision level of accuracy in only one day of tracking.
The solar powered, 1150kg. t-GT spacecraft towing performance evaluation was performed in a 200 day simulated operation in which the t-GT was stationed 155 meters forward of the NEO center of mass along its velocity vector. A very simple control law was employed to maintain the spacecraft within a “box” centered on this nominal location. No control problems or unusual excursions were experienced during the months of towing which produced the desired velocity change of ~0.07cm/sec. During towing a NEO acceleration of 0.22 microns/sec/day was achieved at a fuel expenditure of approximately 0.05 kg/day.
The study confirms that a t-GT spacecraft can determine the orbit of an asteroid accurately enough to assess whether or not it is on an impact course with Earth, even if that course must pass through a relatively small keyhole first. Furthermore, towing operations by such a spacecraft will work with a simple and robust spacecraft design. Finally, the GT towing capability is adequate to assure that an asteroid does not pass through a return keyhole, whether such threat arises naturally (e.g. Apophis in 2029) or as the result of a preceding
primary deflection impulse."
Maybe you can bring your analysis to the table so we all understand why the gravity-tractor approach would not work...
K wrote:
The "cranks" over at JPL don't seem to think so:
Snort. Based on Nasa's performance in the last 20 years in the big project domain I'd say that's a pretty thin recommendation.
The analysis verified the viability of the transponder-Gravity Tractor (t-GT) spacecraft to perform these critical deflection functions.
Go through all the NASA analysis on and prior to NASP. You'll see plenty of analysis verifying viabilities of something that was found to be utterly unworkable for the state of the art at the time.
Anonymous wrote:
Snort. Based on Nasa's performance in the last 20 years in the big project domain I'd say that's a pretty thin recommendation.
JPL's track record of getting unmanned spacecraft to an intended location elsewhere in the solar system is actually pretty respectable.
Go through all the NASA analysis on and prior to NASP. You'll see plenty of analysis verifying viabilities of something that was found to be utterly unworkable for the state of the art at the time
The obvious implication being that since there is "plenty" that is worthless, there must by definition be some that isn't.
Brock wrote:
Regardless of the merits of any particular approach (and let's try more than one, eh?), we all know the UN is where actionable tasks are sent to die, so it really doesn't matter all that much. The only thing that will happen is that a couple years from now a committee will issue a report that real space agencies with real budgets will just ignore.
My hope is that in the next couple decades a private firm will prove out the technology necessary to mine asteroids, and that this expertise and tech will be easily applied to any real threats that may appear. The most I am really hoping for governments to do is launch a few survey satellites designed from the ground up to map asteroid and comet threats (like Canada did recently, but more exhaustively).
Larry J wrote:
action teams for the U.N. Committee
Man, that just got added to my list of all-time great oxymorons.
Andy Freeman wrote:
The UN has an asteroid response team?
I didn't know that there were women and underage children on asteroids.
Martin wrote:
"Anonymous wrote:
Maybe you can bring your analysis to the table so we all understand why the gravity-tractor approach would not work..."
From the JPL study:
"No control problems or unusual excursions were experienced during the months of towing which produced the desired velocity change of ~0.07cm/sec."
Apparently, this might not be a bad approach, if you need a delta-v of no more than 1 mm/s for a small enough asteroid. But what if you need 1 cm/s? Or 1 m/s? And not for something of the order of 20-50 m in diameter. But for something of order 1 - 10 km in diameter? (And why you'd want to stand-off from an object and let gravity do the talking I don't know - why not anchor your ship to the object and push on it directly?)
The only realistic option for deflecting asteroids in extremis are nuclear weapons - a technology that NASA personnel are forbidden from talking about.
I recently saw a talk by Donald Yeomans, author of the study you mentioned and director of the NEO program at JPL. He mentioned a number of ways of deflecting impactors. He indicated (he did not say, he indicated) that the only serious methods were 1.) kinetic impactors if the object is small enough, or 2.) nuclear weapons if it is large.
If the earth faces the dire threat of impact, would you want to rely on some crackpot idea of the kind one sees at an AIAA conference? I'd prefer to rely on a proven technology. Nuclear weapons work. They move metal.
And involving the UN certainly won't help. The UN doesn't help anything.
K wrote:
Let's just cut to the chase.
JPL has the codes to do gravitational assist celestial mechanics and needs funding to keep the ricebowls of the guys who run those codes filled. NASA has R&D funding to keep those bad ol' asteriods away. Obvious result: Grav assist asteroid towing study. Obvious result #2: Grav assist towing proposal computes as great idea. Send more money.
Obvious result #2 gets inserted into the NASA PR machine slot and comes out in every popular science magazine on earth, causing the army of drooling NASA fanboys to lock themselves in the bathroom to dream of assisting well hung NASA administrators in saving the universe.
End of line.
Anonymous wrote:
Apparently, this might not be a bad approach, if you need a delta-v of no more than 1 mm/s for a small enough asteroid. But what if you need 1 cm/s? Or 1 m/s? And not for something of the order of 20-50 m in diameter. But for something of order 1 - 10 km in diameter?
The delta V required is inversely proportional to the warning time. Clearly, massive objects that are discovered with relatively little warning before Earth impact would require other methods.
(And why you'd want to stand-off from an object and let gravity do the talking I don't know - why not anchor your ship to the object and push on it directly?)
For a variety of reasons, some probably manageable, some more difficult. 1) How do you anchor it to a surface, the characteristics of which you know little about? 2) How do you land/anchor on an object that is tumbling in two or more axes? 3) If you manage to land, how do you manage the thrust vector, given that you're probably tumbling in two or more axes? (it may seem intuitive that ANY perturbation would be desirable, but if you steer it into another keyhole, all bets are off)? 4) Can you deploy a spacecraft on the surface with enough fuel to impart the required delta V?
NASA has R&D funding to keep those bad ol' asteriods away. Obvious result: Grav assist asteroid towing study. Obvious result #2: Grav assist towing proposal computes as great idea. Send more money.
The problem with your argument is that the funding for this study did not come from "NASA R&D funding". It came from the B612 Foundation.
Martin wrote:
"Anonymous wrote:
The delta V required is inversely proportional to the warning time. Clearly, massive objects that are discovered with relatively little warning before Earth impact would require other methods."
And clearly, these are the objects which pose the greatest risk to people, and about which, plans - such as they are - should be drawn.
Anonymous wrote:
And clearly, these are the objects which pose the greatest risk to people, and about which, plans - such as they are - should be drawn.
They are not necessarily the ones that pose the greatest risk, as they are the ones most likely to be observed/characterized early. It is the small to medium size objects that are of the greatest concern–the ones that are not easily observable, and which may threaten with little warning.
You are correct, that a variety of solutions need to be developed to deal with a range of potential impactors, but again, given enough warning time, the gravity-tractor is capable of dealing with the large majority of the potential threats.
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About this Entry
This page contains a single entry by Rand Simberg published on October 1, 2008 6:17 AM.
From the article:
"Schweickart said that the report has just been delivered to one of the action teams for the U.N. Committee on the Peaceful Uses of Outer Space, starting the ball rolling for consideration of the panel's recommendations. "Nothing happens in the United Nations without a very structured procedure, and nothing happens fast," he said."
That sounds like a good reason for NOT involving the UN. I think that there ought not to be a procedure in place for dealing with asteroid impacts. Such an occurence would be a (up to now) singular event for humanity - it ought to be treated as such. Procedures delude people into thinking that everything is under control, when it isn't.
Schweickart is a crank. He's pushing the idea of using a "gravity tractor" to pull asteroids around, an idea which is a load of crap. Especially if you are dealing with a potential impactor.
Schweickart is a crank. He's pushing the idea of using a "gravity tractor" to pull asteroids around, an idea which is a load of crap. Especially if you are dealing with a potential impactor.
The "cranks" over at JPL don't seem to think so:
"Summary Statement by B612 Foundation regarding its contract with JPL
to conduct a detailed performance analysis of a transponder equipped
Gravity Tractor spacecraft."
A successful NEO deflection campaign will involve several key functional elements, including the ability to, in situ, precisely determine the orbit of a threatening NEO prior to and post deflection, and to precisely adjust the NEO’s orbit to assure its successful passage between return keyholes at the time of its closest approach to Earth. B612’s contract with
JPL called on it to quantify these two critical capabilities.
The analysis verified the viability of the transponder-Gravity Tractor (t-GT) spacecraft to perform these critical deflection functions. A full report of this work is now available on the B612 website at http://www.b612foundation.org/press/press.html, #18.
In summary a 140 meter diameter equivalent, Hayabusa-shaped NEO, with a rotation period of 6 hours was approached by the t-GT spacecraft with the initial task of determining a precise orbit for the NEO. Effective convergence in the orbit determination was reached after approximately 8 days of tracking and resulted in about a 5 meter (one sigma) error ellipse projected forward 18 years in time. A second orbit determination was performed following a simulated kinetic impact deflection during which the t-GT functioned as a standoff observer. The post-deflection orbit determination converged to the pre-deflection precision level of accuracy in only one day of tracking.
The solar powered, 1150kg. t-GT spacecraft towing performance evaluation was performed in a 200 day simulated operation in which the t-GT was stationed 155 meters forward of the NEO center of mass along its velocity vector. A very simple control law was employed to maintain the spacecraft within a “box” centered on this nominal location. No control problems or unusual excursions were experienced during the months of towing which produced the desired velocity change of ~0.07cm/sec. During towing a NEO acceleration of 0.22 microns/sec/day was achieved at a fuel expenditure of approximately 0.05 kg/day.
The study confirms that a t-GT spacecraft can determine the orbit of an asteroid accurately enough to assess whether or not it is on an impact course with Earth, even if that course must pass through a relatively small keyhole first. Furthermore, towing operations by such a spacecraft will work with a simple and robust spacecraft design. Finally, the GT towing capability is adequate to assure that an asteroid does not pass through a return keyhole, whether such threat arises naturally (e.g. Apophis in 2029) or as the result of a preceding
primary deflection impulse."
Maybe you can bring your analysis to the table so we all understand why the gravity-tractor approach would not work...
The "cranks" over at JPL don't seem to think so:
Snort. Based on Nasa's performance in the last 20 years in the big project domain I'd say that's a pretty thin recommendation.
The analysis verified the viability of the transponder-Gravity Tractor (t-GT) spacecraft to perform these critical deflection functions.
Go through all the NASA analysis on and prior to NASP. You'll see plenty of analysis verifying viabilities of something that was found to be utterly unworkable for the state of the art at the time.
Snort. Based on Nasa's performance in the last 20 years in the big project domain I'd say that's a pretty thin recommendation.
JPL's track record of getting unmanned spacecraft to an intended location elsewhere in the solar system is actually pretty respectable.
Go through all the NASA analysis on and prior to NASP. You'll see plenty of analysis verifying viabilities of something that was found to be utterly unworkable for the state of the art at the time
The obvious implication being that since there is "plenty" that is worthless, there must by definition be some that isn't.
Regardless of the merits of any particular approach (and let's try more than one, eh?), we all know the UN is where actionable tasks are sent to die, so it really doesn't matter all that much. The only thing that will happen is that a couple years from now a committee will issue a report that real space agencies with real budgets will just ignore.
My hope is that in the next couple decades a private firm will prove out the technology necessary to mine asteroids, and that this expertise and tech will be easily applied to any real threats that may appear. The most I am really hoping for governments to do is launch a few survey satellites designed from the ground up to map asteroid and comet threats (like Canada did recently, but more exhaustively).
action teams for the U.N. Committee
Man, that just got added to my list of all-time great oxymorons.
The UN has an asteroid response team?
I didn't know that there were women and underage children on asteroids.
"Anonymous wrote:
Maybe you can bring your analysis to the table so we all understand why the gravity-tractor approach would not work..."
From the JPL study:
"No control problems or unusual excursions were experienced during the months of towing which produced the desired velocity change of ~0.07cm/sec."
Apparently, this might not be a bad approach, if you need a delta-v of no more than 1 mm/s for a small enough asteroid. But what if you need 1 cm/s? Or 1 m/s? And not for something of the order of 20-50 m in diameter. But for something of order 1 - 10 km in diameter? (And why you'd want to stand-off from an object and let gravity do the talking I don't know - why not anchor your ship to the object and push on it directly?)
The only realistic option for deflecting asteroids in extremis are nuclear weapons - a technology that NASA personnel are forbidden from talking about.
I recently saw a talk by Donald Yeomans, author of the study you mentioned and director of the NEO program at JPL. He mentioned a number of ways of deflecting impactors. He indicated (he did not say, he indicated) that the only serious methods were 1.) kinetic impactors if the object is small enough, or 2.) nuclear weapons if it is large.
If the earth faces the dire threat of impact, would you want to rely on some crackpot idea of the kind one sees at an AIAA conference? I'd prefer to rely on a proven technology. Nuclear weapons work. They move metal.
And involving the UN certainly won't help. The UN doesn't help anything.
Let's just cut to the chase.
JPL has the codes to do gravitational assist celestial mechanics and needs funding to keep the ricebowls of the guys who run those codes filled. NASA has R&D funding to keep those bad ol' asteriods away. Obvious result: Grav assist asteroid towing study. Obvious result #2: Grav assist towing proposal computes as great idea. Send more money.
Obvious result #2 gets inserted into the NASA PR machine slot and comes out in every popular science magazine on earth, causing the army of drooling NASA fanboys to lock themselves in the bathroom to dream of assisting well hung NASA administrators in saving the universe.
End of line.
Apparently, this might not be a bad approach, if you need a delta-v of no more than 1 mm/s for a small enough asteroid. But what if you need 1 cm/s? Or 1 m/s? And not for something of the order of 20-50 m in diameter. But for something of order 1 - 10 km in diameter?
The delta V required is inversely proportional to the warning time. Clearly, massive objects that are discovered with relatively little warning before Earth impact would require other methods.
(And why you'd want to stand-off from an object and let gravity do the talking I don't know - why not anchor your ship to the object and push on it directly?)
For a variety of reasons, some probably manageable, some more difficult. 1) How do you anchor it to a surface, the characteristics of which you know little about? 2) How do you land/anchor on an object that is tumbling in two or more axes? 3) If you manage to land, how do you manage the thrust vector, given that you're probably tumbling in two or more axes? (it may seem intuitive that ANY perturbation would be desirable, but if you steer it into another keyhole, all bets are off)? 4) Can you deploy a spacecraft on the surface with enough fuel to impart the required delta V?
NASA has R&D funding to keep those bad ol' asteriods away. Obvious result: Grav assist asteroid towing study. Obvious result #2: Grav assist towing proposal computes as great idea. Send more money.
The problem with your argument is that the funding for this study did not come from "NASA R&D funding". It came from the B612 Foundation.
"Anonymous wrote:
The delta V required is inversely proportional to the warning time. Clearly, massive objects that are discovered with relatively little warning before Earth impact would require other methods."
And clearly, these are the objects which pose the greatest risk to people, and about which, plans - such as they are - should be drawn.
And clearly, these are the objects which pose the greatest risk to people, and about which, plans - such as they are - should be drawn.
They are not necessarily the ones that pose the greatest risk, as they are the ones most likely to be observed/characterized early. It is the small to medium size objects that are of the greatest concern–the ones that are not easily observable, and which may threaten with little warning.
You are correct, that a variety of solutions need to be developed to deal with a range of potential impactors, but again, given enough warning time, the gravity-tractor is capable of dealing with the large majority of the potential threats.