Sunday, November 17, 2013

Rocks From Space

The recent space object that exploded over Chelyabinsk caused a lot of damage and injuries,  and it could easily have been a lot worse.  This provided a loud warning that got some public attention. 

Since then,  back-page stories have documented several close passes of “extinction-event” and “city-buster” sized objects.  Some of these were seen coming,  some were not. 

Update 4-6-14:  Detection of 1+ kiloton explosions by the nuclear test detection network is attributed to asteroid explosions in the air (bolides),  similar to the Chelyabinsk object.  The frequency of these detections suggests that asteroid impacts upon the Earth are 3 to 10 times more frequent than previously thought.  The vast majority are not detected during approach.  This has serious implications:  these "city busters" are not busting cities merely due to blind luck (not exploding over a city).  

Another story that barely made the evening news was a re-estimate by the experts that the risk of “city-buster” objects was very likely some 7 times higher than previously thought.  Chelyabinsk-like incidents seem likely about every 2-3 decades,  not every century,  just not always over cities.

The clear conclusion:  it is indeed prudent for mankind to address this threat,  now that we are both aware of it,  and technologically capable. 

For the last several years,  there has been an ongoing ground-based sky survey that has found about 90% of the threatening objects of “extinction event” size.  The idea is find them years ahead of any risk they might pose,  so as to enable intervention by some sort of deflection technology.

This kind of ground-based telescopic survey simply cannot see the smaller “city buster” objects until they are very close,  if at all,  for a variety of technical reasons.  There are hours of warning at best,  and for the Chelyabinsk object,  no warning at all because it came at us “out of the sun’s glare”. 

The B612 Foundation has as its mission protection from asteroid strikes.  They have proposed a satellite (or better,  several satellites) located near Venus,  to look outward from the sun for “city busters”.   

This kind of space-based sky survey is technologically feasible.  It would enable years of warning for objects this size. 

Problem:  there are no such satellites,  and nothing is funded to build and launch any.

The objects smaller than “city busters” are thought to be vastly more numerous.  With the kind of technologies we have,  these are unlikely ever to be seen,  except at really short “duck-and-cover”-type warning times,  even with satellites in space looking. 

Update 4-6-14:  B612's Sentinel detector satellite is still unfunded by NASA,  relying entirely on private contributions.  It is thought to have a cost near $400 million.  This is to be an infrared detector looking outward from the orbit of Venus,  and should be far more capable at detecting small asteroids,  even those closer to the sun than Earth,  than any optical telescope survey from Earth (which is blind in all directions except outward away from the sun).  

Problem:  there is no organized way to get a timely warning out,  even within national borders,  much less internationally.

What is needed immediately:  satellites for the “city buster” search,  and an organized international “duck-and-cover” warning system. 

What is needed longer term:  what do you do with your years-of-warning?  How do you deflect threats?

There is no real agreement among the experts on the internal nature of such objects.  History says it is likely that what they do think,  is incorrect.  And,  it is extremely unlikely that remote observation will ever resolve the internal structure question. 

The internal structure and properties of these objects fundamentally controls their response to proposed interventions.  What we do know says the movies are wrong:  you don’t blow them up,  you have to push them aside.  Blowing them up,  especially at the last minute,  would actually make the damage worse (shotgun blast versus a single bullet strike). 

Problem:  we already know they are not all the same in their internal properties. 

We know that the few monolithic rocks survive atmospheric entry to hit the surface,  if larger than a green pea.  Baseball size,  they hit with a really damaging whack.  Basketball-sized,  they start blowing big craters like bombs. 

Most of these objects seem to be internally fractured,  or even just rubble piles very loosely bound together.  These are the “bolides” that explode during entry,  the bigger ones with the force of very large nuclear weapons,  like Chelyabinsk.  Bigger also generally penetrates lower down before exploding,  depending upon how tightly the chunks are bound together.   

So,  how do you push on something that might fly apart at a touch?  In our best guesses,  most of the time,  that’s what you are faced with.

What Do We Need to Do?

Developing deflection schemes will fundamentally require in-situ investigation,  to include looking deep inside these objects to find out how,  and how tightly,  they are bound together.  This can be done with robotics to a point,  but men will have to go eventually.

We will need experimental trials of different deflection techniques.  Again,  this can be done with robotics to a point,  but men will have to go eventually.

Fact:  this ain’t like going to the moon.  This is months-to-years in space (like Mars),  not days.

So,  what about NASA’s latest plan for capturing a small one for return to near-lunar space where we actually can send men?  Two problems:  (1) the single captured object is unlikely to be representative,  and (2) this does not address the technology we need for long-distance manned travel. 

If instead you develop long-distance manned travel,  you kill two birds with one stone.  First,  you enable the necessary manned missions to many different asteroids.  Second,  if only you add a lander,  you can also go to Mars.

So,  what is the smarter space program to have?

Satellites inside Venus to look for city busters.

Set up the warning system for the small duck-and-cover objects.

Work intensely on the fundamental requirements for long distance manned travel;  these are (1) better propulsion,  (2) protection from radiation, (3) sufficient living space properly distributed,  (4) artificial gravity by spin to prevent microgravity diseases,  and (5) adequate long-term food preservation.  Update 11-21-13:  see "Details" below for a description of these 5 enabling items for long-distance manned travel.  

And what are we doing?

A giant rocket we may not even need,  which is based on legacy technology,  the manufacture of which is sited in powerful congressional districts,  and the need for which is mandated entirely by congress.

A capsule capable of days-to-weeks of manned travel to and near the moon,  but completely inadequate for months-to-years in deep space,  with extremely-limited radiation protection capability. 

A space station without a medical centrifuge for finding out “how much artificial gee is enough?”,  but which did teach us (1) how to build things from smaller payloads launched by multiple smaller rockets,  and (2) microgravity diseases will prevent manned travel longer than a year or so,  if we go without artificial gravity.

Some support for three commercial ventures aimed at manned launch to orbit.

None of the other critical enabling items for long-distance manned travel are supported.

None of the enabling satellites for city-buster warning are funded in any way.

No duck-and-cover warning system is being funded,  much less actually organized. 

Recommended:

Write your congressmen and senators about this.  Write the NASA administrator about this.  I do,  but I am just one voice. 

Footnote added 11-24-13:  

A version of this article appeared in the Sunday "Waco Tribune-Herald" newspaper.

Postscript

There are other articles related to asteroid defense that I have written and posted on this site.  If you click the keyword "asteroid defense",  you will see only those articles.  Otherwise,  use the by-date/by-title navigation tool to quickly find them.  My exact recommendations about what to do have evolved a little over time,  you can see that in the various articles.  They are as follows:

11-17-13  Rocks From Space  (this article)
 2-15-13   On the Two Dangers From Space
10-31-09  The Future of NASA Manned Space
7-22-09    On the Future of the US Manned Space Program
4-21-09    On Asteroid Defense and a Good Reason for Having National Space Programs (***)

(***) In point of fact,  I did attend the first IAA international conference on asteroid defense in Granada,  Spain,  April 26-30,  2009,  and I presented a paper there,  shortly after writing this article.  My paper was on electrostatic attraction as an upgrade to the basic gravity tractor asteroid deflection concept.

I got to spend some time with many folks at that meeting,  including ex-astronaut Rusty Schweikart,  and ex-cosmonaut Dumitru Prunariu.  Schweikart was on Apollo 9 and was until recently head of B612 Foundation.  Prunariu was (at least as of 2009) head of the Romanian space program,  supplying cosmonauts (and more) to the Russians.  He flew on Salyut 6,  if memory serves.  I also spent some time with Mark Boslough of Sandia Labs,  who is the bolide explosion expert that most folks call upon.

Update 11-21-13:  Details of the 5 Enabling Items for Long-Distance Manned Travel

(1) better propulsion:  we need higher specific impulse,  but we need it at high thrust levels,  enough not to incur long burn time gravity losses (as with all ion and plasma thrusters today).  It would be nice to have a long-term storable version of liquid hydrogen technology.  We need a megawatt-level flightweight electrical power supply for ion and plasma rockets (such as VASIMR).  I would definitely resurrect and improve the solid core nuclear thermal rocket technology,  that almost flew 4 decades ago.  I would work really hard on bringing gas core nuclear thermal rockets to testable forms.  I would resurrect and improve the old nuclear pulse (explosion) propulsion technology that we know would have worked,  but which we never developed. We also need much less expensive launch to Earth orbit,  at the largest payloads that have commercial need. 

(2) protection from radiation:  there should be a unified standard on how much of what types of radiation are allowable.  This is needed for exploration astronauts,  and for long-term settlers,  and their children.  There should be some experiments done very soon in very-high Earth orbit,  to test and develop water/wastewater tankage as a shielding concept that we could implement in the design of any manned interplanetary vehicle.  These standards will always be empirical best guesses;  we need to recognize that,  and "just get on with it".


(3) sufficient living space properly distributed:  this is an under-represented / too-often-ignored issue,  in too many of the mission designs I have seen.  It is a critical issue,  ask anyone who has ever served time in solitary confinement.  The volume / person ratio is NOT the only thing to consider,  but that number should be minimum around the ISS value,  and should more properly look about like what we flew in the old Skylab station.  The distribution and use of that volume is also critically important.  People need more than just their sense of personal space.  They need both a place to congregate,  and a place to be alone.  That second factor is actually the more neglected of the two.  


(4) artificial gravity by spin to prevent microgravity diseases:  for missions over about 1 year,  this is simply required,  and we might as well face it.  The only physical principle we have for artificial gravity is centrifugal force.  There are two issues with that:  (1) how fast a spin is tolerable to the balance organs,  and (2) how much artificial gravity is enough?  The answer to spin rate is a fuzzy empirical value in the neighborhood of 4 rpm for ordinary folks.  We have never run the experiments to find out the answer to "how much gee is enough?",  and we did not equip our ISS to find out.  


So,  since we evolved at 1 gee here on Earth,  that's the design value,  until and unless someone runs the necessary experiments to find out the therapeutic value we really need.  And bed rest experiments won't find it,  they are a poor analog at best.  For 1 gee at 4 rpm,  you need a 56 meter spin radius.  You do NOT need to build a gigantic and super-expensive ship for that.  You do NOT need a Rube Goldberg contraption of cable-connected modules for that (an accident waiting to happen).  


Build your vessel of modules docked in orbit,  to form a slender baton shape.  Put your astronaut habitat at one end,  and something heavy (the engines) at the other.  Spin it end-over-end.  It's perfectly stable,  as seen in Friday night football games all over America.  You'll find you have no need of a gigantic launch rocket to send them up individually.  It's exactly how we built the ISS.  

Artificial gravity simplifies all sorts of life support issues back to things we already know how to do.  Water and wastewater treatment,  toilet design,  cooking,  bathing,  and proper / effective exercise all depend fundamentally upon gravity in one way or another.  So also (most likely) does successful completion of a pregnancy.  

(5) adequate long-term food preservation:  astronaut "space foods" are the plastic-bag analog to the same canned goods we use down here.  Trouble is,  they don't last as long as the canned goods we are used to.  About 12 to 18 months is their maximum lifetime.  A trip to Mars is 2.5 years in space,  so there's a real problem with food.  


Down here,  we have long solved that problem with real canned goods and frozen foods.  These store for decades,  if not centuries,  but often require meal assembly and cooking processes involving free-surface liquids to produce things that are palatable.  Those cooking processes require gravity,  but we need that anyway!  

Until and unless we find something better,  we will have to use the heavier frozen and canned-good foods.  Fresh foods will require a garden,  and most of what we know how to do in that topic also requires artificial gravity.  

Update 3-12-14:

More Space Rocks --

There were three close asteroid fly-bys in just two days recently.  We get several of these each year,  that is normal.  But 3 in 2 days really is a little unusual.  The warning time with all of these was days or less.  This is a strong hint of a real risk,  one so far mostly unaddressed by humanity.  

The data are tabulated just below.  For reference,  the Earth-moon center-to-center distance is 385,000 km, and the Chelyabinsk object was about 15 meters in size.    


8-meter 2014 EC,  Thursday 3-6-14,   61,600 km miss distance             
30-meter 2014 DX110,  Wednesday 3-5-14,  350,000 km miss distance
10-meter 2014 EF,  Wednesday 3-5-14    about 120,000 km miss distance

Two More "Enabling Items" --

In addition to the 5 "enabling items" listed above to enable long-distance manned space travel,  we also need a supple space suit,  and a way to build in orbit things too large to fit the payload shrouds of our launch rockets.  Both of those get addressed in "On-Orbit Repair and Assembly Facility",  dated 2-14-14.  That includes some good photos of two very good spacesuit prototypes.  

A Place to Safely Test Nuclear Propulsion -- 

We could also use a good,  safe place to test nuclear space propulsion.  That place should provide an easy way to avoid air and water pollution,  and a way to avoid annoying neighbors.  This is especially important with nuclear stuff,  since both routine operations and the inevitable testing mishaps will involve radiation.  

I suggest the moon.  There is no better reason to go back.  





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