Meteor Hazards - Revision history

Jriley: reformat

2007-05-19T11:58:53Z

reformat

Jriley: /* Conclusion */

2007-04-23T12:17:52Z

Conclusion

Jriley: /* Conclusion */

2007-04-23T12:16:42Z

Conclusion

Jriley: /* Sporadic Meteors */ small addition

2007-04-23T12:10:30Z

Sporadic Meteors: small addition

Cfrjlr: /* Conclusion */ typos

2007-04-22T19:22:59Z

Conclusion: typos

Cfrjlr: typos

2007-04-22T19:22:18Z

typos

207.114.17.94: /* Meteor Showers */ minor addition

2007-04-21T11:31:56Z

Meteor Showers: minor addition

Jriley: added conclusion

2007-03-31T12:48:08Z

added conclusion

Strangelv: added hazards box

2007-03-31T02:35:30Z

added hazards box

Cfrjlr: links, spell, sporadic

2007-03-29T04:02:17Z

links, spell, sporadic

Show changes

← Older revision		Revision as of 11:58, 19 May 2007
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−	==Meteor Hazards for a Lunar Settlement==	+	{\|align=right
		+	\|__TOC__
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		+	<font size=5> Meteor Hazards for a Lunar Settlement </font>
		+	----

	The threat represented by meteorites to a lunar settlement is real, but '''not''' insurmountable.		The threat represented by meteorites to a lunar settlement is real, but '''not''' insurmountable.

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 The risk to a lunar settlement of damage from a large meteor strike is comparable to living in an Earthquake zone, like California. The risk is there and we must take it into account in the design of the settlement, but it is '''not''' one of our [[Show Stoppers]]. In fact, the risk of a major hit to a lunar settlement is much lower than the risk of the "Big one" to LA.
-The risk of small meteor hits to people and equipment on the moon again is real and must be addressed in both infrastructure design and operational procedure. It is comparable to the risk of storm damage on Earth in that some of the danger is periodic and some is random. This risk is lower than that from hurricanes on the American Gulf Coast.
+The risk of small meteor hits to people and equipment on the moon again is real and must be addressed in both infrastructure design and operational procedures. It is comparable to the risk of storm damage on Earth in that some of the danger is periodic and some is random. This risk is lower than that from hurricanes on the American Gulf Coast.
 We can address these risks and live with them.

@@ Line 115: / Line 115: @@
 ==Conclusion==
-The risk to a lunar settlement of damage from a large meteor strike is comparable to living in an Earthquake zone, like California. The risk is there and we must take it into account in the design of the settlement, but it is '''not''' a show stopper. In fact, the risk of a major hit to a lunar settlement is much lower than the risk of the "Big one" to LA.
+The risk to a lunar settlement of damage from a large meteor strike is comparable to living in an Earthquake zone, like California. The risk is there and we must take it into account in the design of the settlement, but it is '''not''' one of our [[Show Stoppers]]. In fact, the risk of a major hit to a lunar settlement is much lower than the risk of the "Big one" to LA.
 The risk of small meteor hits to people and equipment on the moon again is real and must be addressed in both infrastructure design and operational procedure. It is comparable to the risk of storm damage on Earth in that some of the danger is periodic and some is random. This risk is lower than that from hurricanes on the American Gulf Coast.

@@ Line 50: / Line 50: @@
 Outside of the showers, there is a lower level constant background of meteors arriving at the Moon and Earth from all directions, throughout the year. These meteors are called "sporadic".
-These cannot be predicted and only rarely will they be spotted far enough in advance to provide any warning at all.
+These cannot be predicted and only rarely will they be spotted far enough in advance to provide any warning at all.  They represent a risk to large exposed structures like solar power equipment but only a small, acceptable risk to small targets like a person.  Again, think in terms of small explosions and not bullets.
 ===The 1178 Event===

@@ Line 116: / Line 116: @@
 ==Conclusion==
-The risk to a lunar settlement of damage from a large meteor strike is comparable to living in an Earthquake zone, like California. The risk is there and we must take it into account in the design of the settlement, but it is '''not''' a show stopper. In fact, the risk of a major hit to a lunar settlement is much lower than the risk of thee "Big one" to LA.
+The risk to a lunar settlement of damage from a large meteor strike is comparable to living in an Earthquake zone, like California. The risk is there and we must take it into account in the design of the settlement, but it is '''not''' a show stopper. In fact, the risk of a major hit to a lunar settlement is much lower than the risk of the "Big one" to LA.
-The risk of small meteor hits to people and equipment on the moon again is real and must be address in both infrastructure design and operational procedure. It is comparable to the risk of storm damage on Earth in that some of the danger is periodic and some is random. This risk is lower than that from hurricanes on the American Gulf Coast.
+The risk of small meteor hits to people and equipment on the moon again is real and must be addressed in both infrastructure design and operational procedure. It is comparable to the risk of storm damage on Earth in that some of the danger is periodic and some is random. This risk is lower than that from hurricanes on the American Gulf Coast.
 We can address these risks and live with them.

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 * Geminids in December
 A major shower occurs about every 30 years. Abraham Lincoln witnessed a major Leonid shower in 1833 from Illinois and described the experience in a speech many years later. The sky was lit up all night with thousands of shooting stars, including many bolides, often with sonic reports like distant cannon. It was thought by many, but not by Lincoln, to be of major religious significance. The end of the world did not come, but such a shower would be a major risk to a lunar settlement.
-There was a major Leonids shower in 1998 that disrupted [[ISS]] operations.  A Russian landing had to be delayed and the crew simply waited it out.  Fortunately there was no major damage.
+There was a major Leonids shower in 1998 that disrupted [[ISS]] operations. A Russian landing had to be delayed and the crew simply waited it out. Fortunately there was no major damage.
-Different locations on the Moon will have different risks from the various showers. The place of the Moon in its orbit will also have an effect. The risk is greatest if your location is exposed to the leading direction in Earth’s orbit at the peak time.  A lunar settlement will need to generate a computer model of all meteor showers as seen from its location and provide alerts of major events.
+Different locations on the Moon will have different risks from the various showers. The place of the Moon in its orbit will also have an effect. The risk is greatest if your location is exposed to the leading direction in Earth’s orbit at the peak time. A lunar settlement will need to generate a computer model of all meteor showers as seen from its location and provide alerts of major events.
 Fortunately the timing of these showers is well known. Known meteor showers may require curtailment of outside manned activities and the placing of equipment in a safe mode for several days a year.
-===Sporadic Metoers===
+===Sporadic Meteors===
-Outside of the showers, there is a lower level constant background of meteors arriving at the Moon and Earth from all directions, throughout the year.  These meteors are called "sporadic".
+Outside of the showers, there is a lower level constant background of meteors arriving at the Moon and Earth from all directions, throughout the year. These meteors are called "sporadic".
 These cannot be predicted and only rarely will they be spotted far enough in advance to provide any warning at all.
@@ Line 112: / Line 112: @@
 All lunar equipment will have to be designed with a safe mode. There are many possible emergencies where the safe mode will be needed.
 ----
 ==Conclusion==
-The risk to a lunar settlement of damage from a large meteor strike is comparable to living in an Earthquake zone, like California.  The risk is there and we must take it into account in the design of the settlement, but it is '''not''' a show stopper.  In fact, the risk of a major hit to a lunar settlement is much lower than the risk of thee "Big one" to LA.
+The risk to a lunar settlement of damage from a large meteor strike is comparable to living in an Earthquake zone, like California. The risk is there and we must take it into account in the design of the settlement, but it is '''not''' a show stopper. In fact, the risk of a major hit to a lunar settlement is much lower than the risk of thee "Big one" to LA.
-The risk of small meteor hits to people and equipment on the moon again is real and must be address in both infrastructure design and operational procedure.  It is comparable to the risk of storm damage on Earth in that some of the danger is periodic and some is random.  This risk is lower than thatfrom hurricanes on the American Gulf Coast.
+The risk of small meteor hits to people and equipment on the moon again is real and must be address in both infrastructure design and operational procedure. It is comparable to the risk of storm damage on Earth in that some of the danger is periodic and some is random. This risk is lower than that from hurricanes on the American Gulf Coast.
 We can address these risks and live with them.
 ----
 {{Hazards}}
 [[Category:Hazards]]
 [[Category:Architecture]]

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 A major shower occurs about every 30 years. Abraham Lincoln witnessed a major Leonid shower in 1833 from Illinois and described the experience in a speech many years later. The sky was lit up all night with thousands of shooting stars, including many bolides, often with sonic reports like distant cannon. It was thought by many, but not by Lincoln, to be of major religious significance. The end of the world did not come, but such a shower would be a major risk to a lunar settlement.
-Different locations on the Moon will have different risks from the various showers. The place of the Moon in its orbit will also have an effect. The risk is greatest if your location is exposed to the leading direction in Earth’s orbit at the peak time.
+Different locations on the Moon will have different risks from the various showers. The place of the Moon in its orbit will also have an effect. The risk is greatest if your location is exposed to the leading direction in Earth’s orbit at the peak time.  A lunar settlement will need to generate a computer model of all meteor showers as seen from its location and provide alerts of major events.
 Fortunately the timing of these showers is well known. Known meteor showers may require curtailment of outside manned activities and the placing of equipment in a safe mode for several days a year.
@@ Line 48: / Line 48: @@
 Outside of the showers, there is a lower level constant background of meteors arriving at the Moon and Earth from all directions, throughout the year.  These meteors are called "sporadic".
 ===The 1178 Event===
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 The report is now taken to be credible, but the exact cause is under debate. The leading theory is that it was a major hit by a meteor on dark area of the Moon that threw ejecta up into the sunlight. This would be largest lunar meteor hit in human history and gives us a good idea of how often lunar settlers should expect a really big one.
-The problem is that this event was ‘’’not’’’ reported elsewhere; not in Europe, not in India, and not in China. All of these societies would have recorded any significant lunar event they witnessed. This puts a limitation of the size and time extent of the event. The visible effects must not have been observable from Earth to the unaided human eye for more than a few hours. More important, there was no report of a major meteor shower in the days that followed.
+The problem is that this event was '''not''' reported elsewhere; not in Europe, not in India, and not in China. All of these societies would have recorded any significant lunar event they witnessed. This puts a limitation of the size and time extent of the event. The visible effects must not have been observable from Earth to the unaided human eye for more than a few hours. More important, there was no report of a major meteor shower in the days that followed.
 One candidate for the 1178 hit site has been put forward. It is [[Crater]] [[Giordano Bruno]] which is a very new crater in the right location. The problem is that Crater [[Bruno]] is too big, about 22 km (14 miles) in diameter. An event that large would have launched thousands of tons of lunar material on paths that would take it to Earth over the next few days. The resulting meteor showers would have been awe inspiring and lasted for days if not weeks. It could not have been missed anywhere on Earth.
-Another possibility is that the monks saw a large bolide, or fireball, in Earth’s atmosphere exactly in front the Moon as seen from Canterbury. The visible effect would have appeared similar to that reported, but would have been visibly associated with the Moon from only a limited area. A sonic report would be expected from such an event, but none was reported.
+Another possibility is that the monks saw a large bolide, or fireball, in Earth’s atmosphere exactly in front the Moon as seen from Canterbury. The visible effect would have appeared similar to that reported, but would have been visibly associated with the Moon from only a limited area. A sonic report would be common from such an event, but none was reported.
-The event could still have been a meteor strike on the Moon, but the resulting crater must simply be very much smaller the Crater Bruno. Probably no more than a few hundred meters. Such an event would be short in time span, limited visually to a small area on Earth, and would not create a notable meteor shower. There are plenty of small candidate craters, but their age is very difficult to judge without a visit.
+The event could still have been a meteor strike on the Moon, but the resulting crater must simply be very much smaller the Crater Bruno. Probably no more than a few hundred meters. Such an event would be short in time span, limited visually on Earth, and would not create a notable meteor shower. There are plenty of small candidate craters, but their age is very difficult to judge without a visit.
 No matter what theory wins in the final analysis, a major meteor strike anywhere on the Moon would be a major problem for a lunar settlement. Most of the danger comes from the ejecta rather than from the initial hit.
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 Lunar meteor strikes large enough to throw dangerous ejecta over significant areas are very rare, but they are still a major danger to a lunar settlement. The ejecta will affect a much larger area than direct meteor hit and can do great damage.
-The effects of lunar ejecta are completely different from similar explosive debris on Earth. First off, much of the energy in an Earth explosion is carried away by the air pressure wave which does not occur on the Moon. At any significant distance from an Earth explosion, air resistance slows the flying debris so that the major danger becomes one of being crushed or buried.
+The effects of lunar ejecta are completely different from similar explosive debris on Earth. First off, much of the energy in an Earth explosion is carried away by the air pressure wave which does not occur on the Moon. Second, at any significant distance from an Earth explosion, air resistance slows the flying debris so that the major danger becomes one of being crushed or buried.
-On the Moon there is no air to slow the debris or to carry off energy as sound waves. The individual rocks will come at you hard and fast. They will not be energetic enough to vaporize on impact like a meteor, but they can act very much like shrapnel from a hand grenade, even at a great distance.
+On the Moon there is no air to slow the debris or to carry off energy as sound waves. The individual ejecta rocks will come at you hard and fast. They will not be energetic enough to vaporize on impact like a meteor, but they can act very much like shrapnel from a hand grenade, even at a great distance.
 The high speed also means there will be little warning. The most reliable warning instrument for events over the horizon would be a [[seismograph]] that reads sound waves traveling through the rocky body of the Moon. The time between the first strong [[seismic]] waves arriving and the first flying rocks arriving could be as little as a few seconds. People outside may need to quickly dive for cover.
@@ Line 93: / Line 96: @@
 People operating of the exposed surface of the Moon will need to have procedures for defensive actions in the event of a meteor warning. These procedures will require periodic practice drills for instant response.
-In the settlement and industrial areas, these procedures may require spider holes for people to run into. These might be slit trenches with a roof covered with sandbags. They would require the people to remain in their [[spacesuit]]s but would provide spare air and power. They would also provide some radiation protection. Such spider holes might also be used in the event of rocket landing or launching accidents. They could also provide protected places for electronics, communication nodes, power distribution nodes, and robot recharging stations.
+In the settlement and industrial areas, these procedures may require spider holes for people to run into. These might be slit trenches with a roof covered with sandbags. They would require the people to remain in their [[spacesuit]]s but would provide spare air and power. They would also provide some radiation protection. Such spider holes might also be used in the event of rocket landing or launching emergencies. They could also provide protected places for electronics, communication nodes, power distribution nodes, and robot recharging stations.
-In the open field, these procedures might involve hiding under a [[lunar rover]] or jumping into a small crater. Even a large rock might be better than nothing, if you knew which side to hide on.
+In the open field, emergency procedures might involve hiding under a [[lunar rover]] or jumping into a small crater. Even a large rock might be better than nothing, if you knew which side to hide on.
-===Safing Equipment===
+===Safeing Equipment===
 Large equipment, such as [[Sandworms]], cannot be brought inside in a meteor shower. The best we will be able to do is to place the equipment in a safe mode to minimize the damage from a hit.
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 All lunar equipment will have to be designed with a safe mode. There are many possible emergencies where the safe mode will be needed.
 {{Hazards}}