Keeping Asteroids at Bay
from Gerhard Holtkamp, 31. October 2010, 01:11
Did dinosaurs become extinct because they didn't have a space program? A select group of people around the world think so and feel that mankind can do better...
So far over half a million asteroids have been found in the solar system. The vast majority are Main Belt Asteroids which stay between the orbits of Mars and Jupiter. But over 6500 asteroids are so called NEOs (Near Earth Objects). NEOs either cross the Earth orbit or at least come close enough to cause concern.
A small asteroid of about 50 meters hitting the Earth would pack the power of an atom bomb while an object of 200 meters could easily wipe out a whole country. Larger still and you get destruction on a continental scale or even the annihilation of human civilization.
Luckily the impact probability drops almost exponentially with size. While about 100 tons of micrometeroids bombard the Earth every day with almost all of it burning up in the atmosphere and never posing any threat you would have to wait about 5000 years on average for a 100 meter asteroid to release about as much energy as the largest H-bomb ever detonated.
So why bother? The most you and I are ever likely to see is a scenic meteor shower! There seem to be more urgent problems in this world. Severe weather, earthquakes and tsunamis are in the news all the time requiring immediate attention. But this doesn't mean that we should simply forget about the threat of NEOs for the time being. There are two good reasons for it: Rare as they may be if a large enough asteroid hits the Earth the consequences can be much more severe than the worst other natural disasters and unlike hurricanes or tsunamis where all we can hope for is a more timely forecast we can actually do something about NEOs.
This week a workshop on NEO mission planning and operations was held at the European Space Operations Centre ESOC ending with a media briefing on Friday, 29-OCT-2010 which I was able to attend.
As there was no immediate threat (nobody expected the meeting to be ended prematurely by an asteroid hitting ESOC) a pragmatic approach of relatively modest projects was proposed building on what has already been done during the past decade. There is general agreement that NEOs are a global issue that have do be dealt with on a global international scale comprising all the major space agencies as well as the United Nations.
Anyone present at the briefing (or having seen the live webcast) who expected sensational new developments on how to combat asteroids Hollywood style may have been disappointed. The focus of the workshop had been on recommendations for global coordination and response. The Head of the Association of Space Explorers Committee on NEOs and former Apollo 9 astronaut Rusty Schweikart put it this way: Dealing with NEOs is less a technical issue (we already have the technology needed) but primarily a bureaucratic problem!
Schweikart also mentioned that Europe with its long experience of having to get many nations to agree on common politics would be well poised to play a significant role.
Detlef Koschny who is in charge of the NEO segment of ESA's Space Situational Awareness program outlined the current European activities in this field. Over the next two years a NEO Precursor Survice will be established with a central database for Europe's NEO information to be set up. This is in collaboration with already existing European resources (observatories, catalogues, networks and expertise). A capability to analyse possible impacts and mitigations as well as a system to alert civil authorities in Europe would be part of the ESA NEO segment.
The best database and the best scenarios how to deal with asteroids would be useless if you don't know where those objects are. With existing observatories (some of them operate automatically) the majority of objects larger than 1 km in size have probably been detected. A few more specialized telescopes will be needed to catch most objects even below 100 m as these are much more frequent and as such pose a more immediate threat.
Despite all the high tech in space operations ordinary citizens can still participate in a meaningful way. Detlef Koschny made special mentioning of the role amateur astronomers play in discovering new asteroids. To acknowledge their work a group from a nearby amateur observatory (having quite a number of discoveries to their credit) had been invited as special guests.
Had it not been for a question at the end of the briefing the media would have stayed in the dark on what could be done in case an asteroid came flying along with the address of our planet written on it. The surprisingly simple answer is to just ram a spacecraft into the asteroid with sufficient energy. This will cause a slight change in velocity which in turn will cause enough deviation in the NEOs orbit to make it miss our beloved planet. The cost for such a mission would be similar to a typical planetary mission - quite affordable.
Like everything dealing with spaceflight the basic ideas are normally easy to grasp but working out the details can be haunting. In order for the ramming scheme to work the orbit must be known with high precision and well in advance of any encounter. Only then can the small velocity change cause enough deviation in the long run. There is also some finetuning needed which would be provided by a second nearby spacecraft acting as kind of a tugboat.
But much more research is needed before one could reliably fly such a mission. Depending on their individual histories asteroids can be anything from solid rock to a conglomerate of rubble. The effect of ramming a spacecraft into an asteroid will be very different depending on the internal structure of the body. An mission to try out this method on an actual asteroid had been studied in detail some years ago by ESA under the name of Don Quijote but we were told this project has been shelfed for the moment.
Once the size of an asteroid gets larger than 300 or 400 meters this simple ramming method will no longer produce enough velocity change to be effective. Detonating a nuclear device close to the asteroid might help (and keep Hollywood happy) but those scenarios are not being considered. As such an event is expected to occur only once in a few hundred thousand years it is better to await new developments in science and technology and rather concentrate on the much more likely events that can be handled with currently available tools.
Another class of objects that we are defenseless for the moment are comets on hyperbolic orbits originating from the far reaches of the solar system. Such comets are typically detected a few years (or more often a few months) before they reach the inner solar system. This is too short a time to get an accurate orbit and send a spacecraft for the encounter. Luckily studies suggest that these objects are even less likely to hit the Earth than large asteroids.
(It is the opinion of this blogger that far into the future a system of high power space based lasers would be available with the task of propelling laser driven light sails to the outer edges of the solar system and beyond. These lasers could easily cope with such comets in quick response. But once again this is something nobody will bother about for a very long time. Just excuse me - after all I have called my blog SpaceTimeDREAMER!)
So it looks like we are doing better than those dinosaurs - or do we? Well, dinosaurs had been dominating our planet for some 150 million years while mankind has entered the stage only fairly recently. We have a long way to go...
So far over half a million asteroids have been found in the solar system. The vast majority are Main Belt Asteroids which stay between the orbits of Mars and Jupiter. But over 6500 asteroids are so called NEOs (Near Earth Objects). NEOs either cross the Earth orbit or at least come close enough to cause concern.
A small asteroid of about 50 meters hitting the Earth would pack the power of an atom bomb while an object of 200 meters could easily wipe out a whole country. Larger still and you get destruction on a continental scale or even the annihilation of human civilization.
Luckily the impact probability drops almost exponentially with size. While about 100 tons of micrometeroids bombard the Earth every day with almost all of it burning up in the atmosphere and never posing any threat you would have to wait about 5000 years on average for a 100 meter asteroid to release about as much energy as the largest H-bomb ever detonated.
So why bother? The most you and I are ever likely to see is a scenic meteor shower! There seem to be more urgent problems in this world. Severe weather, earthquakes and tsunamis are in the news all the time requiring immediate attention. But this doesn't mean that we should simply forget about the threat of NEOs for the time being. There are two good reasons for it: Rare as they may be if a large enough asteroid hits the Earth the consequences can be much more severe than the worst other natural disasters and unlike hurricanes or tsunamis where all we can hope for is a more timely forecast we can actually do something about NEOs.
This week a workshop on NEO mission planning and operations was held at the European Space Operations Centre ESOC ending with a media briefing on Friday, 29-OCT-2010 which I was able to attend.
As there was no immediate threat (nobody expected the meeting to be ended prematurely by an asteroid hitting ESOC) a pragmatic approach of relatively modest projects was proposed building on what has already been done during the past decade. There is general agreement that NEOs are a global issue that have do be dealt with on a global international scale comprising all the major space agencies as well as the United Nations.
Anyone present at the briefing (or having seen the live webcast) who expected sensational new developments on how to combat asteroids Hollywood style may have been disappointed. The focus of the workshop had been on recommendations for global coordination and response. The Head of the Association of Space Explorers Committee on NEOs and former Apollo 9 astronaut Rusty Schweikart put it this way: Dealing with NEOs is less a technical issue (we already have the technology needed) but primarily a bureaucratic problem!
Schweikart also mentioned that Europe with its long experience of having to get many nations to agree on common politics would be well poised to play a significant role.
Detlef Koschny who is in charge of the NEO segment of ESA's Space Situational Awareness program outlined the current European activities in this field. Over the next two years a NEO Precursor Survice will be established with a central database for Europe's NEO information to be set up. This is in collaboration with already existing European resources (observatories, catalogues, networks and expertise). A capability to analyse possible impacts and mitigations as well as a system to alert civil authorities in Europe would be part of the ESA NEO segment.
The best database and the best scenarios how to deal with asteroids would be useless if you don't know where those objects are. With existing observatories (some of them operate automatically) the majority of objects larger than 1 km in size have probably been detected. A few more specialized telescopes will be needed to catch most objects even below 100 m as these are much more frequent and as such pose a more immediate threat.
Despite all the high tech in space operations ordinary citizens can still participate in a meaningful way. Detlef Koschny made special mentioning of the role amateur astronomers play in discovering new asteroids. To acknowledge their work a group from a nearby amateur observatory (having quite a number of discoveries to their credit) had been invited as special guests.
Had it not been for a question at the end of the briefing the media would have stayed in the dark on what could be done in case an asteroid came flying along with the address of our planet written on it. The surprisingly simple answer is to just ram a spacecraft into the asteroid with sufficient energy. This will cause a slight change in velocity which in turn will cause enough deviation in the NEOs orbit to make it miss our beloved planet. The cost for such a mission would be similar to a typical planetary mission - quite affordable.
Like everything dealing with spaceflight the basic ideas are normally easy to grasp but working out the details can be haunting. In order for the ramming scheme to work the orbit must be known with high precision and well in advance of any encounter. Only then can the small velocity change cause enough deviation in the long run. There is also some finetuning needed which would be provided by a second nearby spacecraft acting as kind of a tugboat.
But much more research is needed before one could reliably fly such a mission. Depending on their individual histories asteroids can be anything from solid rock to a conglomerate of rubble. The effect of ramming a spacecraft into an asteroid will be very different depending on the internal structure of the body. An mission to try out this method on an actual asteroid had been studied in detail some years ago by ESA under the name of Don Quijote but we were told this project has been shelfed for the moment.
Once the size of an asteroid gets larger than 300 or 400 meters this simple ramming method will no longer produce enough velocity change to be effective. Detonating a nuclear device close to the asteroid might help (and keep Hollywood happy) but those scenarios are not being considered. As such an event is expected to occur only once in a few hundred thousand years it is better to await new developments in science and technology and rather concentrate on the much more likely events that can be handled with currently available tools.
Another class of objects that we are defenseless for the moment are comets on hyperbolic orbits originating from the far reaches of the solar system. Such comets are typically detected a few years (or more often a few months) before they reach the inner solar system. This is too short a time to get an accurate orbit and send a spacecraft for the encounter. Luckily studies suggest that these objects are even less likely to hit the Earth than large asteroids.
(It is the opinion of this blogger that far into the future a system of high power space based lasers would be available with the task of propelling laser driven light sails to the outer edges of the solar system and beyond. These lasers could easily cope with such comets in quick response. But once again this is something nobody will bother about for a very long time. Just excuse me - after all I have called my blog SpaceTimeDREAMER!)
So it looks like we are doing better than those dinosaurs - or do we? Well, dinosaurs had been dominating our planet for some 150 million years while mankind has entered the stage only fairly recently. We have a long way to go...
