Asteroid 2024YR4 Threat

This object has been identified as a Type S (“stony”) or possibly a Type L object.  It would be a dry,  loose rubble pile of cobbles,  gravel,  sand,  and possibly some boulders,  just barely held together by vanishingly-weak gravity. 

This object was discovered after it had already passed by at closest approach.  So much for advanced warning.  It is currently headed out away from the sun (and us) on its approximately 4-year-long orbit,  that crosses Earth’s orbit two places.  Earth can be there when it is also there,  at only one of them,  apparently the outbound crossing in this case.  It will return for another close pass in late 2028,  and again in late 2032.

It is the 2032 close pass that is of concern for this object striking the Earth.  Its size is such that this is a “city buster”,  not an extinction event.  The initial estimate of the probability of a collision was in the neighborhood of 1%,  raised to around 2%,  then to about 3%,  then lowered again to near 1.5%.  The point:  we just do not really know anything,  except that there is a risk. 

Update 2-26-2025:  NASA has lowered the risk to about 0.0027%,  and ESA to 0.001%,  for a collision with Earth.  However,  NASA says there is still a 1.7% chance the asteroid could hit the moon.,  Information is from a news story posted on the PBS Newshour website. 

As for deflection,  yes,  there are nuclear warheads,  and yes,  there are rockets that could send them to it.  But the guidance and control items,  and the warhead fuses,  do not yet exist for this purpose,  nor are they likely to,  in the next 4 years.  Most of the deflection methods we could use risk disrupting the rubble pile asteroid,  turning a single bullet strike into a widespread shotgun blast.

The close pass in 2028 offers an opportunity to find out more of what we need to know:  (1) better orbital data,  and (2) its physical properties.  Some sort of craft orbiting it could determine its mass with precision.  Some sort of impactor or explosive experiment might provide information about how easy it might be to disrupt this object versus deflecting it.  Time is very short to put “something” together!

The “brute force” mission is to launch right at the close pass,  so that upon achieving the right speed in the right direction,  you have already rendezvoused with the asteroid.  2028 would be the right time to do this.   2032 is too late,  in terms of the collision risk.  The figure shows the rough estimate I made for this mission. 

Lists of Some Articles By Topic Area

Search code 21102021

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Update 8-2-2026:     added multiple articles to multiple topics below. 

Update 2-10-2026:  added several to multiple topics below.

Update 6-10-2025:  added several to multiple topic areas below.

Update 4-10-2025:  added several to multiple categories below.

Update 4-7-2024:  added 3 to rocket,  below.

Update 3-6-2024:   added 3 to rocket,  below. 

Update 2-13-2024:  added 1 to ramjet and 6 to rocket, etc. below.

Update 10-1-2023:  added "Basic Thermal Results for High Speeds" to 2 topics below.

Update 9-2-2023:  added "Purported SR-72 Propulsion" to 3 topics below. 

Update 7-18-2023: added 1 article to forensics.  

Update 6-21-2023:  added 2 articles to rocket ballistics and vehicle performance list.

Update 5-4-2023: added 1 article each to aerothermo and forensics lists.

Update 2-4-23:  added new nozzles article to aerothermo and ballistics lists.

Update 1-1-23:  added catalog topic for towed decoys,  this text color.

Update 12-2-2022:  two ramjet articles added to that topic list,  this color.

Update 9-5-2022:  some recent articles added to the lists,  this text color.

Update 10-1-2022:  some others added,  this color.

Update 10-30-2022:  a couple added,  this color.

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I was once an all-around ramjet design,  development,  and test engineer,  among many other things,  including rocket work.  This was mostly at a plant in McGregor,  Texas,  once known as Rocketdyne or Hercules.  Part of that reservation is where SpaceX tests rockets now. 

I did just about everything there was to do,  for this ramjet work.  There are very few indeed with knowledge and experience this comprehensive,  I was definitely not a narrow specialist!  But my knowledge and abilities,  in each of all these different specialty disciplines,  was actually quite substantial and deep!  

My design analyses usually took the form of custom hand-calculations,  not just sitting there blindly running other people’s computer codes.  (Although,  I did use computer codes,  and even wrote some myself.)  I have informally published several articles on my blog site that describe how some of this ramjet work was done.

Ramjet & Closely-Related Articles (there are others,  but these are the best):

9-1-2025:            On Pressure Vessels

6-1-2024:            Ramjet Ablative Liners

4-23-2024:          Presenter at Workshop (NC State U meeting on high temperature materials)

2-13-2024           GW's Ramjet Book Is Now Available 

10-1-2023            Basic Thermal Results for High Speeds

9-1-2023              Purported SR-72 Propulsion

12-2-2022            The Unchoked Gas Generator As A Throttle For Gas Generator-Fed Ramjets

12-1-2022            How Ramjets Work

10-30-22              Plasma Sheath Effects in High Hypersonic Flight

6-1-22                  About Hypersonic Vehicles

11-2-21                The “Warm Brick” Ramjet Device (nonpropulsive application to an infrared decoy)                                 [also the 11-2-21 update to this catalogue list]

10-1-21                Use of the Choked Pintle Valve for a Solid Propellant Gas Generator Throttle

8-2-21                  The Ramjet I Worked On the Most

7-1-21                  Another Ramjet I Worked On

11-9-20                Fundamentals of Inlets

3-3-20                  Ramjet Flameholding

2-16-20                Solid Rocket Analysis (applies to ramjet for boosters)

2-4-20                  One of Several Ramjets That I Worked On

1-2-20                  On High-Speed Aerodynamics and Heat Transfer

11-12-18              How Propulsion Nozzles Work

7-4-17                  Heat Protection Is the Key to Hypersonic Flight

6-12-17                Shock Impingement Heating Is Very Dangerous

12-10-16              Primer on Ramjets

12-21-12              Ramjet Cycle Analyses

These are located on http://exrocketman.blogspot.com,  along with many others on a wide variety of subjects. 

There is a navigation tool on the left of that page.  For the article you want,  you only need its publication date and its title.  Use the navigation tool:  click on the year,  then the month.  Then click on the title if you need to.  The data you need are in these lists.

If you click on one of the figures,  you can see all of them enlarged.  You see nothing but the figures,  though.  There is an “X-out” from this view,  upper right of screen.

At the end of any given article,  there is also a list of search keywords assigned to it.  If you click on “ramjet”,  you will only see the articles bearing that keyword.  The same is true of the other keywords.

Here follows a photo of one of the ramjets I worked on:  ASALM-PTV.  It is hanging under the wing of an A-7 Corsair-II,  an aircraft my father designed.  I always considered this photo a sort of “family portrait”. 

 

ASALM-PTV Ramjet Vehicle Underwing of A-7 Corsair-II

Some of those ramjet articles overlap with the next list.  That next list is of aerothermodynamics and heat transfer-related articles.  Some of these relate to high-speed atmospheric flight,  and others to atmospheric entry from space.  Those two scenarios are quite different,  in that atmospheric flight is a steady-state equilibrium problem,  while atmospheric entry is mostly a transient heat-sinking problem.  The search keyword for these is “aerothermo”.  Clearly,  I was adept at multiple specialties.

Aerothermodynamics & Heat Transfer Articles:

8-2-2026            What Nozzle Designs to Use Where, &Why

7-1-2026            Quick First Cut at Orion Entries (lunar)

6-1-2026            Entry Study (probes+Apollo, Earth & Mars)

5-1-2026            Entry By-Hand (how-to article)

4-28-2026          Preliminary Evaluation of Artemis-2 Heat Shield

3-01-2026          Ramjet Data Re: Heat Shields  

2-1-2026               Rocket Nozzles

11-2-2025             Get Acquainted Info: High Speed Vehicles

4-12-2025             Ballistic Coefficient Study for Earth Entry

7-2-2024               Recent Heat Protection Items, 3 of 3

6-1-2024               Ramjet Ablative Liners

5-23-2024:            Entry Concept Screening

4-23-2024:            Presenter at Workshop (NC State U meeting on high temperature materials)

1-2-2024              Airplanes on Mars?

12-9-2023            Overall Study Results:  Propellant From Moon

11-22-2023          How the Suborbital "Hopper" Calculations Were Made and With What

11-21-2023          Upgraded Rocket Hopper As Orbit Taxi

11-4-2023            Surface Freight Transport On Mars (not actually rocket,  but related)

11-1-2023            Rocket Hopper For Mars Planetary Transportation

10-1-2023            Basic Thermal Results for High Speeds

9-1-2023              Purported SR-72 Propulsion

5-1-23                  Heat Shields

2-4-23                  Rocket Nozzle Types (bells and aerospikes)

9-18-22                Plasma Sheath Effects in Hypersonic Flight

7-3-22                  Early High-Speed Experimental Planes

6-1-22                  About Hypersonic Vehicles

4-1-20                  Entry Heating Estimates

1-2-20                  On High-Speed Aerodynamics and Heat Transfer

1-9-19                  Subsonic Inlet Duct Investigation

1-6-19                  A Look At Nosetips (Or Leading Edges)

1-2-19                  Thermal Protection Trends For High-Speed Atmospheric Flight

11-12-18              How Propulsion Nozzles Work

7-4-17                  Heat Protection Is the Key to Hypersonic Flight

6-12-17                Shock Impingement Heating Is Very Dangerous

11-17-15              Why Air Is Hot When You Fly Fast

8-4-13                  Entry Issues

3-18-13                Low-Density Non-Ablative Ceramic Heat Shields

1-21-13                BOE Entry Analysis of Apollo Returning From the Moon

1-21-13                BOE Entry Model User’s Guide

8-19-12                Ballute Drag Data

8-19-12                Blunt Capsule Drag Data

7-14-12                “Back Of the Envelope” Entry Model

I was also a rocket propulsion engineer,  mostly in solid composite propellants.  However,  from the chamber outlet through the nozzle,  the ballistics of all rockets are the same,  including liquid propellant rockets.  If you can allow for any gas bled off and dumped overboard for turbopump operation,  then the very same ballistics apply,  right down to the chamber pressure vs flow rate calculation. 

Further,  the estimation of vehicle performance from the simple rocket equation can be made quite accurate,  if you know how to apply “jigger factors” in the appropriate places for gravity and drag losses,  and if you know what values of these “jigger factors” to apply.  I have been very successful at doing this kind of work. The following list shows that,  and mostly shares the “launch” and “space program” keywords.  While still a graduate student,  I spent a summer doing advanced configuration and mission work at what was then LTV Aerospace,  working on its "Scout" 4-stage solid satellite launcher. 

Rocket Ballistics and Rocket Vehicle Performance articles:

8-2-2026          What Nozzle Designs to Use Where, &Why

7-26-2026        Kudos to SpaceX for Flight 13

7-1-2026           Quick First Cut at Orion Entries (lunar)

6-1-2026           Entry Study (probes+Apollo, Earth & Mars)

5-27-2026         Kudos to SpaceX for Flight 12 

5-19-2026         Launch to Low Orbit Study (SSTO, TSTO)

5-18-2026         Launch Vehicle Rough-Out (SSTO, TSTO)

4-28-2026         Preliminary Evaluation of Artemis-2 Heat Shield

4-14-2026         Elliptic Departure and Arrival

2-21-2026         Space-Based AI?  Not Easy!

2-1-2026              Rocket Nozzles

1-1-2026              Landing Pads for Rocket Vehicles

12-1-2025            Criteria for Rough-Field Landings

11-11-2025          Where Should the New Space Stations Be Located?

10-16-2025          Going Back to the Moon

9-1-2025              On Pressure Vessels

8-1-2025               Air Launch to Low Earth Orbit

7-26-2025             Tank Design for Easy Cryogenic Transfers in Weightlessness

6-23-2025:            Starship Explosion (forensics)

6-1-2025               SpaceX “Starship” Flight Test 9 

5-1-2025              Vehicle Assembly and Refueling Facility in LEO

4-1-2025              About Nuclear Pulse Propulsion

3-13-2025            Rough/Soft Field Space Landings

3-7-2025              Upper-Stage Starship Failure,  Test 8

3-2-2025              Spin Gravity

2-21-2025            Asteroid 2024YR4 Threat

2-9-2025              There Is Nothing As Expensive As a Dead Crew

2-1-2025              Exploring Mars Is Not Settling Mars

1-25-2025            Initial Study for Tug Missions LEO to LLO

1-2-2025              SpaceX's Starship As a Space Tug (update looks at Centaur)

12-1-2024            Tug-Assisted Arrivals and Departures

11-1-2024            Getting to Low Earth Orbit and Back

10-13-2024          Starship/Superheavy Flt. Test 5,  13 Oct '24

10-1-2024            Elliptic Capture

9-13-2024            What Went Wrong? (problems with Starliner and at Boeing in general )

9-1-2024              Rocket Equation-Based Launch Vehicle Analyses

7-2-2024              Recent Heat Protection Items, 3 of 3

5-3-2024              Entry Concept Screening

4-23-2024            Presenter at Workshop (NC State U meeting on high temperature materials)

4-4-2024              Ascent Compromise Design Trade Study

4-3-2024              Bounding Analyses for TSTO

4-2-2024              Bounding Calculations for SSTO Concepts 

2-25-2024            Tricky Landing

3-3-2024              Launch to Low Earth Orbit:  1 or 2 Stages?

3-4-2024              Launch to Low Earth Orbit:  Fixed Geometry Options

9-1-2023              Purported SR-72 Propulsion

6-20-23                TSTO Launch Fundamentals

6-6-23                  Frontal Thrust Density In Rockets

2-4-23                  Rocket Nozzle Types (bells and aerospikes)

10-27-22              Getting to Low Earth Orbit  (vertical ballistic launch versus lifting ascent)

10-1-22                Rocket Engine Calculations (how to rough-out or reverse-engineer, ex: Raptor-2)

9-7-22                  Two-Stage Reusable Spaceplane Rough-Size (VTO HL both stages)

8-4-22                  Engineering Lander/Rover for Mars

5-1-22                  Investigation:  "Big Ship" Propellant From the Moon vs From Earth (added to list as part of Update 5-1-22)

4-2-22                  Earth-Mars Orbit-to-Orbit Transport Propulsion Studies (added to list as part of Update 5-1-22) 

2-1-22                  A Concept for an On-Orbit Propellant Depot

8-18-21                Propellant Ullage Problem and Solutions

3-15-21                Reverse Engineering Estimates: Starship Lunar Landings

3-9-21                  Reverse-Engineering Starship/Superheavy 2021

3-5-21                  Fundamentals of Elliptic Orbits (delta-vee requirements)

2-9-21                  Rocket Vehicle Performance Spreadsheet (rocket vehicle performance)

7-13-20                Non-Direct to the Moon with 2020 Starship

7-5-20                  How the Spreadsheet Works (Starship to Mars)

7-5-20                  2020 Starship/Superheavy Estimates for the Moon

7-3-20                  Cis-Lunar Orbits and Requirements

6-21-20                2020 Starship/Superheavy Estimates for Mars

5-25-20                2020 Reverse Engineering Estimates for Starship/Superheavy

2-16-20                Solid Rocket Analysis (solid ballistics & more)

11-21-19              Interplanetary Trajectories and Requirements

10-22-19              Reverse-Engineering the 2019 Version of The Spacex “Starship” / “Super Heavy” Design

9-26-19                Reverse-Engineered “Raptor” Engine Performance (liquid ballistics)

9-16-19                Spacex “Starship” as a Ferry for Colonization Ships

9-9-19                  Colonization Ship Study

11-12-18              How Propulsion Nozzles Work (rocket, ramjet, & turbine; plain & free-expansion)

9-11-18                Velocity Requirements for Mars

8-23-18                Back-of-the-Envelope Rocket Propulsion Analysis (rocket vehicle performance)

4-17-18                Reverse Engineering the 2017 Version of the Spacex BFR

10-23-17              Reverse-Engineering the ITS/Second Stage Of the Spacex BFR/ITS System

3-18-17                Bounding Analysis for Lunar Lander Designs (rocket vehicle performance)

3-6-17                  Reverse-Engineered “Dragon” Data (rocket vehicle performance)

8-31-13                Reusable Chemical Mars Landing Boats Are Feasible (rocket vehicle performance)

In 2009,  I attended an asteroid defense conference in Granada,  Spain,  as a poster paper presenter.  I have since written some articles about asteroid defense.  Unfortunately,  the asteroid defense capability picture hasn’t changed much since my 2009 attendance at that conference.  Again,  the latest are the best and most up-to-date.   Be aware that “NEO” (Near Earth Object) includes comets as well as asteroids as threats.  Comets may be the more difficult to defend against,  because of the surprise nature of the detection and orbits.  These articles all share the “asteroid defense” keyword.

Asteroid Defense Articles:

5-8-2025               Re-Entering Space Junk Threats

2-21-2025            Asteroid 2024YR4 Threat

8-30-20                Asteroid Threats  (current status assessment:  not good)

6-3-20                  On the Manned Spacex Launch

7-14-19                Just Mooning Around (asteroids plus Mars)

12-13-13              Mars Mission Study 2013 (what takes you to Mars takes you to asteroids)

4-21-09                On Asteroid Defense and a Good Reason for Having National Space Programs

I have also applied my wide-ranging knowledge to the problems of atmospheres to breathe while in space,  and the kinds of spacesuits that might best serve our needs.  Again,  the latest is the best and most up-to-date.  But I have been looking into these issues for some time,  as indicated by the dates on these articles.  These all share the “spacesuit” keyword.

Space Suits and Atmospheres Articles:

7-8-2025              Oxygenation Issues for Habitats and Space Suits

1-2-22                  Refining Proposed Suit and Habitat Atmospheres (update 1-2-22) best case and easiest-to-remember cases,  plus an independent estimate of the utter min suit pressures feasible

1-1-22                  Habitat Atmospheres and Long-Term Health (update 1-1-22)  adds a long term hypoxia criterion for the habitat in addition to short term criteria for the min-P suit

3-16-18                Suit and Habitat Atmospheres 2018

11-23-17              A Better Version of the MCP Spacesuit?

2-15-16                Suits and Atmospheres for Space

1-15-16                Astronaut Facing Drowning Points Out Need for Better Space Suit

11-17-14              Space Suit and Habitat Atmospheres

2-11-14                On-Orbit Repair and Assembly Facility

12-13-13              Mars Mission Study 2013

1-21-11                Fundamental Design Criteria for Alternative Space Suit Approaches

One of my favorites is the MCP (mechanical counter pressure) version of the spacesuit.  This was pioneered by Dr. Webb in the 1960’s as a possible suit for the Apollo missions to the moon.  It is not a full pressure suit at all,  but essentially a tight garment that simply squeezes the body.  It is porous,  so that you sweat right through it to cool,  just like ordinary street clothing.  But this design was tested quite successfully in 1968 for 30 minutes in a vacuum chamber,  at way above the equivalent “vacuum deathpoint” altitude.  Photo follows:

Webb’s MCP Space Suit:  Helmet,  Backpack,  and Supple Garment Total 85 Lbs

The reason why I like this approach over Dava Newman's designs is that Webb's designs are essentially vacuum-protective underwear that can be easily laundered.  Over them you wear whatever unpressurized clothing you need for protection from from heat,  cold,  and mechanical hazards.  All of these are separate,  easily laundered items.  I think the "one garment that does everything" approach,  that we have been using since about 1960,  is wrong.  "Mix and match" is way more flexible.

Besides vacuum death and microgravity disease,  there is also a radiation hazard to worry about in space.  But,  it is not quite what you think:  there are two completely different hazards to worry about.  On Earth,  we have two kinds of protection:  the atmosphere,  and the magnetic field.  In low Earth orbit,  we have only the magnetic field.  Outside the magnetic field,  going to the moon or anywhere else,  there is no protection.  Yet these things can be quantified,  and some of it shielded fairly effectively.  What got me started on this topic were the dangers posed by the nuclear disaster in Fukushima,  Japan.  Keyword “radiation”.

NASA has since lowered its career exposure limits below the older values I had obtained from them.  That avoids the slight chance of cancer late in life due to galactic cosmic ray exposure over long times in space.  But,  it makes passive shielding design bulkier,  heavier,  and more difficult to design.  It's really a trade-off.  However,  NASA still has not faced up to the erratic but intense floods of radiation from solar eruptions.  They haven't yet killed a crew from this,  although they came close to that during Apollo.  But if they don't address this,  they will kill a crew,  once we move out beyond the Van Allen belts,  and try to stay there.  That includes the return to the moon.  

Radiation Hazard Articles:

10-5-18                Space Radiation Risks:  GCR vs SFE

4-11-15                Radiation Risks for Mars Trip

5-2-12                  Space Travel Radiation Risks

3-24-11                Radiation and Humans

3-17-11                Follow-Up On the Japan Nuclear Crisis

3-15-11                On the Nuclear Crisis In Japan

On a lighter note,  I have long been interested in pulsejet engines,  especially valveless pulsejets.  While teaching math at TSTC,  Waco,  I became involved with mentoring a student who was also interested in pulsejets.  I and a colleague assisted this student in making his own valveless pulsejet engines,  which attention and involvement also turned this student into an “A” student in math!  Keyword “pulsejet”.

That student built a small engine that eventually pushed an old golf cart around,  and then a much bigger engine which we together fired up out here on my farm homestead.  Photos of the two engines follow:

Smaller Student-Built Valveless Pulsejet Engine (Later Pushed a Golf Cart)

Larger Student-Built Valveless Pulsejet Engine

Pulsejet Articles:

5-20-12                Recommended Broad Design Guidelines For Valveless Pulsejet Combustors

4-30-12                Big Student Pulsejet an Even Larger Hit at TSTC

3-6-12                  Student Pulsejet a Hit at EAA Meeting

11-12-11              Student Pulsejet Project

I have been interested in ethanol fuels since my early days in college.  When I went to work for what is now Minnesota State University,  after my 20-year career in aerospace defense work ended,  I got more serious about it.  My next job was at Baylor University in Waco,  Texas,  and it dealt directly in alternative fuels for aircraft.  The scope of that included ethanol (and an ether) as piston-engine fuels,  and biodiesel-jet fuel blends as turbine fuels,  plus STC work with the FAA,  and also experimental engineering research work,  as well as classroom teaching. 

Not too long after leaving Baylor,  I began my own experimental engineering research at home,  using E-85 ethanol fuel,  and stiff ethanol blends,  in a variety of vehicles.  Those would include straight E-85 ethanol fuel in an old farm tractor and in an old-time air-cooled VW beetle,  plus stiff ethanol blends in a variety of completely-unmodified cars and 4-stroke lawn and garden equipment.  I basically recommend up to E-35 blend strength,  as a “drop-in” fuel,  for just about any 4-stroke piston engine. 

The keywords are “ethanol” and “old cars” for most of these articles.  Once again,  the latest is the best and most up-to-date.

Articles About Ethanol and Ethanol Blends in Vehicles:

9-1-21                  Making Stiff Blends At the Gas Pump

11-3-13                Aviation Alternative Fuel Compatibility Issues

11-2-13                An Update on Ethanol Fuel Use

8-9-12                  Biofuels in General and Ethanol in Particular

5-4-12                  Energy Storage: Batteries vs Unpressurized Liquid Fuels

6-12-11                Another Red-Letter Day

5-5-11                  Ethanol Does Not Hurt Engines

2-12-11                “How-To” For Ethanol and Blend Vehicles

11-17-10              Nissan Mileage Results on Blends

11-12-10              Stiff Blend Effects in Gasoline Cars

12-15-09              Red Letter Day:  Ethanol VW Experiment Complete

7-1-09                  Another Antique Comes Out of Storage

I have returned part-time out of retirement to help a friend with his auto repair business.  I was once ASE-certified as a condition of employment while teaching at Minnesota State in its Automotive and Manufacturing Engineering Technology department.  Before that,  I did most of my own automotive maintenance and repair work.  Accordingly,  I have posted some articles about basic car care,  plus one funny.  These all share the “old cars” and “fun stuff” keywords. 

I have since gone back into retirement.  My friend now has a real mechanic,  who knows more than I do,  and is much more experienced,  and faster. 

Automotive Care Articles:

8-22-22                Automotive Work (another "funny")

3-4-22                  Understanding Your Tires (added to this list as update 5-1-22)

12-3-20                Blinker Fluid (the “funny”,  and it is a sight gag)

8-20-20                Underhood Check

7-25-20                Taking Care of Car Batteries

When I returned to the rocket plant in McGregor for my second employment there,  the family and I acquired an old farm outside McGregor as our home.  We have been there ever since.  This place was largely covered in shin- to knee-high prickly pear cactus,  so thick there were few trails through it.  After grubbing it out of the house’s back yard with hand tools,  I decided there had to be a better way to do this cactus eradication. 

I tried a variety of mechanical drags behind my old farm tractor for some 15 years without success.  The results were always the same:  it looked better for a while,  but returned worse than ever before,  within months.  My neighbor was trying shredding at 1 inch off the ground.  Eventually that worked,  but required the neighbor to be out there shredding,  every single day,  the same ground over and over,  for 6 (or more) years.  The neighbor also tried spraying herbicides on one patch of ground,  which took 3 years to show results,  but then totally reinfested within another 2 years.

I then tried to build a “scooper-upper” out of scrap steel.  The idea was to bust the aboveground cactus loose from its roots,  and catch it on a tarp towed behind the “scoop-upper”,  for disposal in a burn pit.  It completely failed to work,  because when the tool hit the cactus and busted it loose from its roots,  it fell forward in front of the tool,  instead of backward onto the deck.  The tool then just ran over the top of the cactus debris.  I gave up in disgust when this failure-to-scoop happened.

I went back up a few months later to salvage the steel,  and saw something totally unexpected:  the cactus was dead and gone wherever the tool had been towed!  Grass was growing in the cow pasture where the cactus had been.  It did not take very long to understand that the aboveground cactus foliage had been crushed and damaged passing underneath the heavy tool,  such that the pads dried out and died,  before they could put down new roots from the thorn sites in contact with soil.  They had completely composted away over those months.

I “played” with this tool to get it just “right”,  and started killing acres of prickly pear quite effectively,  and with very little time and effort involved.  In fact,  I still have this very same experimental prototype,  and it still works today.  This prototype led to me filing a patent on the cactus tool in 2002. 

I revised the design to something more producible from real steel stocks,  and built two production prototypes that worked just as well as the original experimental prototype,  but were easier to build.  Then,  with the patent in hand as of 2004,  I began building and selling these tools to the public.  My first customer wouldn’t wait for a real production tool,  and insisted on buying one of the two production prototypes.  I still have the other one.  I still use it,  and it now serves as an experimental test bed for new features,  too.

As time went by,  it quickly became apparent that other folks had rockier land,  or land with tree stumps.  I changed the design twice,  to add a heavier stabilizing snout,  plus a “barge front” wedging surface to get over small rock outcrops.  This was quite successful,  and is embodied in the tools still built and sold today.

A close friend wanted to do cactus-killing for hire,  and bought a “one-off” design from me.  I also helped him build and modify a few more tools,  until the “commercial version” was defined:  a really tough snout,  a big “barge front”,  and retractable wheels to facilitate stepping over obstacles,  plus easier loading up ramps onto trailers. 

When that friend retired,  I revised his “commercial” design into something that used a common core tool chassis with my “homeowner grade” plain tool.  This common core chassis had the big barge front,  and used either a tough snout for the “plain tool”,  or a longer tough snout for the “hydraulic tool”,  that was also fitted with retractable wheels operated hydraulically.  I sell both versions to this very day.  Both are towed on a chain bridle behind a farm tractor’s drawbar.

I am working on a third version that could be an alternative implement affixed to the hydraulic boom of a skid-steer loader.  It uses an already-available “universal” adapter plate to accomplish this,  as a quick-change item.  There is nothing to report here yet about that project,  but the “plain” and “hydraulic” tools are well-described in a series of articles on “exrocketman” under the keyword “cactus-killing”. 

These two versions are shown in the photo,  with the plain tool in the foreground,  and the hydraulic tool in the background.

Foreground:  Plain Tool;  Background:  Hydraulic (Wheeled) Tool

The new skid-steer version has been tested and revised to a form that not only works,  but is more easily manufacturable.  It is now patent pending. 

Articles Related to Cactus Eradication:

2-9-17                  Time Lapse Proof It Works

7-30-15                New Cactus Tool Website

1-8-15                  Kactus Kicker Development

1-8-14                  Kactus Kicker:  Recent Progress

10-12-13              Construction of the Plain Cactus Tool

5-19-13                Loading Steel Safely (Cactus Tool)

12-19-12              Using the Cactus Tool or Tools

11-1-12                About the Kactus Kicker

12-28-11              Latest Production Version of the Kactus Kicker

 Update 12-1-2021:  these articles are more-or-less forensic analyses of various events:

7-26-2026          Kudos to SpaceX for Flight 13

6-9-2026            Close Call at Newark

5-27-2026          Kudos to SpaceX for Flight 12

6-23-2025            Starship Explosion (forensics)

6-1-2025               SpaceX “Starship” Flight Test 9

3-13-2025            Rough/Soft-Field Space Landings

3-7-2025              Upper-Stage Starship Failure,  Test 8

2-9-2025              There Is Nothing As Expensive As a Dead Crew

10-13-2024          Starship/Superheavy Flight Test 5,  13 Oct 2024

9-13-2024            What Went Wrong?  (problems with Starliner and at Boeing)

7-7-23                  On the loss of the "Titan" Submersible  (added 7-18-23)

4-25-23                Starship/Superheavy Flight Test

12-1-21                The Seal Failure in the SRB That Doomed Challenger

12-10-20              Spacex Test Flight Results in Explosion

9-1-20                  On the Beirut Explosion

5-4-18                  Some Thoughts on the Anniversary of the West Explosion

11-1-14                Two Commercial Spaceflight Disasters in One Week

7-9-13                  On the Asiana 214 Crash

7-9-13                  On the Train Wreck in Quebec

4-18-13                Fertilizer Explosion in West,  Texas

9-23-11                Air Races,  Air Shows,  and Risks

6-3-10                  Plenty of Blame to Go Around for the Disaster in the Gulf

5-20-10                It really was the North Koreans who sank the South Korean ship

Update 1-1-23:  these are the articles related to towed decoys:

Between my tenures at the McGregor rocket shop,  I worked at what was then Tracor Aerospace in Austin,  Texas,  doing aircraft and ICBM countermeasures work.  The bulk of this related to towed aircraft decoys,  which are more advanced aircraft countermeasures against missiles than the traditional chaff and flares.  I did all sorts of lab,  wind tunnel,  and flight tests with these things.  To a great extent,  I had to design my own tests,  test hardware,  and equipment,  too. 

Tracor Austin became part of British Aerospace after I left to go back to the rocket shop in McGregor,  and it closed entirely,  only somewhat later.  When you combine the typical corporate management misbehavior with the massive defense industry contraction that happened after the fall of the Soviet Union,  this plant closure outcome is entirely unsurprising.  That was as true for the rocket shop as well as for Tracor.  And it is why I had to leave the aerospace defense industry entirely,  after being laid off in late 1994 due to the rocket plant closure in McGregor.

My work at Tracor in towed aircraft decoys related to two distinct types of decoys:  towed hard body decoys,  and towed ribbons.  The hard bodies are exactly that:  some sort of small airframe towed behind the aircraft that it is intended to protect,  on some sort of towline.  These could be radar (RF) decoys to replace chaff,  or they could be infrared (IR) decoys to replace flares and jammers.  I worked on both of these towed decoy types (RF and IR).  Towed RF decoys are now operational with the air forces of multiple nations,  because they really work.

The towed ribbon decoys are quite different,  being rather similar to windsocks and soft towed gunnery targets.  The technologies supporting this concept apply only to RF,  and are restricted to only extreme-low observables aircraft.  I also worked on these.  One huge issue is stable tow for extended periods of time,  when the “flapping-flag” effect wants to destroy them in mere seconds at jet aircraft speeds. 

Obviously,  deployment,  especially very rapid deployment,  is another huge issue with these ribbon decoys,  as well as with the hard body decoys. Solving it requires expertise in dynamics as well as aerodynamics,  plus knowledge of all sorts of mechanisms. 

Here is the list of my towed decoy articles available as of this update.  Future updates may add more. 

1-1-23                  Towed Hardbody Decoys  (could IR or RF)

11-2-21                The “Warm Brick” Ramjet Device (nonpropulsive application to an infrared decoy)   

Later                     possible articles on deployment and on towed ribbons

Asteroid Threats

Update 10-25-2022:  NASA's DART successfully impacted Dimorphos,  and got a larger deflection than estimated beforehand.  The debris tails (there are two) were a surprise to NASA.  There is little data yet regarding the impact crater size or how close it came to disrupting the rubble-pile asteroid.  

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Update 11-4-2021:  From AIAA’s email newsletter “The Daily Launch” for Thursday 11-4-2021:

Asteroid Passes By Earth Without Being Detected Until It Was Gone

SPACE (11/3) reports that an “asteroid about the size of a refrigerator shot past Earth last week, and astronomers didn’t know the object existed until hours after it was gone.” Scientists “were unaware of the object, dubbed Asteroid 2021 UA1, because it approached Earth’s daytime side from the direction of the sun.”

My take on this:  This was yet another dayside approach from sunward that absolutely cannot be detected with any sort of telescope on the Earth or in orbit about the Earth.  Such objects can only be detected by something located more sunward than the Earth,  looking out away from the sun.   This particular story was first reported a week earlier,  and was presented here as update 10-29-2021. 

Atacama Desert Site Of Ancient Comet Impact

CNN (11/3) reports that researchers believe the Atacama Desert in Chile “was the site of an ancient comet explosion intense enough to create giant slabs of silicate glass.” The minerals found in the desert glass “matched up with particles collected by NASA’s Stardust mission, which sampled a comet known as Wild 2.” Study author and Brown University Professor Emeritus of Geological Science Pete Schultz said, “This is the first time we have clear evidence of glasses on Earth that were created by the thermal radiation and winds from a fireball exploding just above the surface.”

        The Daily Mail (UK) (11/3) reports that the glass fragments collected by Brown University researchers “contained exotic minerals such as cubanite and troilite only found in meteorites and other extraterrestrial rocks.”

My take on this:  This is yet another example of why a deflection technology and the means to deliver it,  are necessary.  Especially for comets,  where the warning will often be days not years. 

Update 10-29-2021:  It keeps happening!  Sooner or later we are going to be hit by one of these things!  From the AIAA email newsletter "Daily Launch" for today (emphasis/yellow highlighting is mine---

Asteroid Performs Third-Closest Fly-By Of Earth

CNET News (10/28) reports that Asteroid 2021 UA1 “sped by Antarctica on Sunday without any advance warning and narrowly avoided being fully incinerated by Earth’s atmosphere.” The two meter diameter asteroid’s fly-by was the third-closest of Earth that “didn’t end in an impact.”

Update 8-26-2021:

 From AIAA’s “Daily Launch” email newsletter for 8-26-2021 (yellow highlight mine):

Asteroid Deflection May Require Multiple Attempts

The New York Times (8/25) reports that researchers presented findings on asteroid deflection research at the 84th annual meeting of the Meteoritical Society this month. The researchers found that kinetic impact deflection is a feasible and potentially effective means of sending an asteroid out of the way of Earth. Researchers found that carbon-rich meteorites were more likely to shatter when hit with high-velocity aluminum spheres.

Bear in mind that the carbon-rich asteroids and meteorites are the most numerous type. Examine Figure 4 below,  for why this is an important finding.  

Update 9-26-2020:

Asteroid 2020 SW was discovered 9-18-2020,  and made its closest approach on 9-24-2020.  The warning time was thus 6 days.  It was estimated to be 5-10 m in size.  Closest approach distance was 22,000 km. 

Using the somewhat-arbitrary density of 2.5 g/cc = 2500 kg/cu.m,  that corresponds to a mass between 49.7 and 398 metric tons.  This definitely falls in the city-buster range for speeds between 10 and 20 km/s,  if it were to impact the surface,  or explode close to it. 

Given 6 days notice,  it might have been possible to evacuate a threatened city.  This one could have been a "success" story,  rare among those listed in the article. 

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Original article:

In 2009 I attended a meeting held in Spain about defending Earth from threatening asteroid impacts.  At that time,  we had been able to locate most of the large (extinction-event) objects,  we were starting efforts to locate the smaller “city-buster” objects,  and we had some ideas about how to deal with them.  

I'm sorry to report that not much has changed since then.  We are now beginning to find some of the smaller "city-busters",  but that's about it.

Recent public news accounts:

Asteroid 2020QG passed ~1830 miles from Earth on Sunday 8-23-20.  It was not seen until some 6 hours after it passed.  This object was 10-20 feet (3-6 m) in diameter (for those unfamiliar with metric,  a meter is about 10% longer than a yard). Its speed past the Earth was ~27,600 mph.  An on-line animation in Wikipedia shows ~12.3 km/s at ~9300 km center-to-center.

Asteroid 2018VP1 is predicted to pass Earth Monday 11-2-20 (the day before election day in the US),  give or take ~2 days,  depending upon whose estimate you believe.  It is said to be 6.5 feet in size. It is listed in Wikipedia as 2-4 m size,  with an animation that shows a fairly-slow 9.7 km/s pass,  about 419,000 km center-to-center away (not far outside the moon's orbit). 

A somewhat-recent event,  only a few years ago:

The Chelyabinsk object was about 20 m dia,  with 19.16 km/s velocity,  estimated at 12,000-13,000 metric tons.  It exploded in the atmosphere,  with a yield estimated at 400-500 KT-equivalent to a nuclear weapon (where 1 KT = 4.184 GJ). This thing fell 2-15-2013,  and was completely undetected before its entry. It injured around 1000 people,  and blew out most of the windows in that city.

Here are the data as listed in Wikipedia,  for the previous 2 years,  plus this one so far.  To this I added the Chelyabinsk object.  It would take more than a day to evacuate a city that was threatened by such an event,  which is why the measure of warning time is important.   That list is in Figure 1.

So,  note the warning times color-coded in the list.  Only the single green one might have afforded sufficient time to evacuate.  Note also that a center to center distance under 6.37 thousands of km is a direct impact,  because that figure is the radius of the Earth.

Figure 1 – List of Small Asteroids Recently

Conclusion:  our track record seeing the small ones before they pass is NOT good at all,  whether or not we include the Chelyabinsk object!

What’s still coming that we know of:

Here are the predictions for some selected future encounters,  per Wikipedia,  as Figure 2.  To this I added the recently-reported "election day" object. The notation "LD" refers to lunar distance.  If "yes",  the predicted encounter leads to a pass within the orbit of our moon.  Bear in mind that both measurement inaccuracies and any sort of disturbance can throw these close-pass center-to-center distances off. 

Figure 2 -- Known Future Threats

The point here is that we already know of some larger objects that will pass uncomfortably close in the coming years.  Smaller objects are more numerous,  and mostly as-yet undetected.  That means there are a lot of “city busters” out there,  some of which we can expect to hit us.  This threat is quite real!

Figuring the explosive yield range of air bursts and impacts:

Chelyabinsk object:  20 m dia sphere has 4189 cu.m volume.  Using middle-of-the-road mass 12,500 tons = 12.5 E6 kg,  density is mass/volume = 2984 kg/cu.m.  Fresh water is 1000 kg/cu.m,  so the specific gravity is about 2.98.  How consolidated that object was,  is unknown.  But it's the best data available to me.   Most minerals are in this range of density.

A "typical" small asteroid is 2-6 m in size.  Treating that as the diameter of a sphere,  "typical" volumes are 4.19-113 cu.m.  Using the Chelyabinsk object estimate of 2980 kg/cu.m density,  the "typical" masses are 12,500 kg = 12.5 metric tons,  up to 337,000 kg = 337 metric tons. 

The actual astronomers have better data to use in such calculations than I have,  but their methods and formulas,  and mine,  are the same.  This stuff is just not as certain as it often appears to the public.

About the lowest velocity ever seen is near 10 km/s,  and about the highest velocity to be expected is nearer 20 km/s,  at least as a good guess.  Kinetic energy is 0.5 mass x velocity squared,  where for mass in kg and velocity in m/s,  you get energy in Joules:  kg m^2/s^2 = N-m = J.  Every 4.184 billion Joules is a kiloton (KT) equivalent to a nuclear weapon.

I used these data to estimate the results in Figure 3.

Figure 4 – Kinetic Energy As Equivalent Nuclear Weapon Yield

These figures say that these 2-6 m size "small asteroid" objects will have energies comparable to nuclear warheads in the 150 KT to 16 MT range.  They are very definitely "big-city-busters"! 

For comparison,  the Hiroshima and Nagasaki bombs were about 15 and 20 KT in yield.  Many of our military warheads are now in the 200 KT range.  The giant "Tsar Bomb" test,  of October 1961 in the Russian arctic,  was around 66 MT,  the largest nuclear explosion ever seen.

Not only are these real city-buster threats,  we also have a poor track record of seeing them until it is too late! That is precisely because they are small,  dark,  and often approach from a more sunward direction,  where our ground-based telescopes are blind.

There are differences with nuclear weapon effects:

The kinetic energy of these things is not the whole story,  unlike nuclear weapons.  There are also the tremendous interplanetary speeds,  and the downward angle of the entry trajectory. 

Unlike a nuclear weapon,  the fireball associated with an air burst is still traveling along the trajectory at great speed for a while.  If during that interval,  it gets close to (or impacts) the surface,  it will incinerate everything in the vicinity.

Downward angle plays a strong role,  too.  The Chelyabinsk object struck at a very shallow angle across the sky,  so that its air burst happended dozens of miles up in the air. Had this been steeper downward,  the burst would have been much closer to the city,  utterly destroying it,  and killing its people. 

A little steeper still,  and the object might have struck the surface without bursting in the air.  That just releases even more blast and heat right at the impact point. 

What we need:

(1) We need to be able to detect these things,  in time to actually do something about them! 

(2) We need to obtain real ground-truth data directly from them,  so that we can figure out exactly what to do,  given the chance. 

(3) We need to implement those means of doing something,  which includes both the means to get there fast enough,  and the actual means to deflect or destroy them.

Detection:

The B612 Foundation at one time proposed an asteroid-defense satellite to be placed in an orbit nearer that of Venus than Earth, so that it could see threats approaching Earth from sunward,  by being even more sunward,  but looking outward from the sun. 

The sensor of this proposed satellite was not based on visible light or radar,  but infrared.  These objects are brighter and easier to see in the infrared than in visible light (or radar),  although they are still dim.

We still need that satellite,  and preferably 2 or 3 of them at any one time!  We do not have any of them!  What we do have (mostly telescopes based on Earth),  is having great difficulty seeing things that are only 1-100 m in size. 

That is because (1) these telescopes are not located sunward of Earth looking outward at dark,  cold deep space,  and (2) they does not use infrared (asteroids,  being somewhat near the sun,  are simply warmer than the cold of deep space).

Knowing how to deflect or destroy:

There seem to be three general types of these small objects. (1) By far the most numerous are those that seem to be made of a mix of carbonaceous and stony particles,  not very consolidated (and often with significant void spaces internally),  and actually rather weak structurally. 

These are essentially flying sand-and-gravel-and-boulder piles, which would fly completely apart if you actually pushed against one. These are the ones that tend to explode up in the atmosphere,  from the suddenly-crushing drag forces of encountering air while moving at interplanetary speeds. 

The small solid particles of post-explosion debris,  if larger than about a quarter inch diameter,  actually do not burn up entirely,  and hit the ground at modest speeds.

(2) There are a few asteroids that are really more-or-less solid rocks,  made of a mix of different minerals,  and even some metal content.  These tend to hang together fairly well,  and would likely not fly apart out in space,  if you pushed against one,  at least fairly gently. How internally fractured they really are,  is an open question.

These bodies tend to make it to the Earth's surface,  if larger than about a quarter inch.  Not being debris of an atmospheric explosion,  they are moving very much faster when they hit,  causing their own explosions and craters.

(3) There are a very,  very few that are actually solid chunks of metal,  mostly iron.  If larger than about a quarter inch,  they make it through the atmosphere to strike at very high velocities as one solid object.

This produces really big explosions and craters.  Meteor Crater in Arizona was created about 50,000 years ago by one of these,  just about the size of the objects we are interested in detecting and deflecting-or-destroying.

Some of these we could push against (in some way) and deflect into a miss,  if we could get there in time to do it.  But not the most-numerous unconsolidated bodies.  Those will fly apart if pushed,  creating a storm of debris. 

If that disruption of the threatening object happens close to the Earth,  then you just turned a damaging bullet strike into an even more damaging shotgun blast!  That strategy is viable only if you can do it far enough from the Earth that most of the debris storm you have created will miss.  See Figure 4.

Figure 4 – Bullet Strike vs Shotgun Blast,  with Timing

Deflection / destruction techniques:

Space is a vacuum.  There is nothing out there to propagate a blast wave.  Nuclear explosions create great heat as radiant energy,  but no blast out there.  You won't have time to drill (and we don't know how to drill into these things anyway) to emplace a nuclear bomb inside one of these bodies.

What you do is detonate your nuclear device alongside the threat.  The immense amount of radiant heat will vaporize and spall-off significant mass from it,  hopefully without completely disrupting it.  The resulting momentum "kick" in the opposite direction will subtly alter the body's trajectory.  Do this "right",  and "soon enough",  and you can cause it to miss.

The same sort of thing can be done with impactors instead of nuclear weapons.  You hit the thing from the right direction,  and "soon enough",  and the impact creates the spall-off,  just on a smaller scale than a nuclear explosion.  The momentum reaction changes the body's course slightly,  provided that it is not disrupted.  See Figure 5. 

 

Figure 5 – How Spallation Creates a Force

The gentlest technique is the so-called "gravity tractor".  This takes the longest time to have effect,  so you must know (and go) years in advance of the impact threat to Earth. You send a spacecraft to rendezvous,  and hover,  alongside the body. 

Its propulsion prevents its falling onto the body.  But the tiny force of gravity between spacecraft and body forces the body to "follow the spacecraft".  This is a very tiny effect,  but it is real.  See Figure 6.

Figure 6 -- Gravity Tractor

To summarize – see Figure 7.

Figure 7 -- Actions We Can Take,  with Timing

What to do about this:

Now look carefully at the indicated timing required in Figure 7,  and compare that to the track record seeing these threats in advance of their approach in Figure 1.  It is NOT GOOD!  We should be working on this,  but are mostly not.  THAT is why we need the detection satellites.

Getting there soon enough to do any good:

For an Earth-crossing asteroid,  there is a short window of time to get there from here,  and a very demanding propulsion requirement to do the mission,  even if a one-way trip with an unmanned spacecraft.  The perihelion velocity of the asteroid is substantially higher than the Earth in its orbit about the sun,  by at least 2-3 km/s. 

What you have to do to get there is wait until the Earth is in the "right place" in its orbit about the sun,  relative to where the asteroid is. You cannot go "just any time you want",  like we can to the moon.  Then you escape from the Earth,  and wait in an Earth-like orbit about the sun for the asteroid to catch up with you.  Then you burn a second time to catch up with the faster asteroid. 

The cost of all this (14+ km/s) is more than a direct one-way shot to Mars at optimum orbital positions (about 12 km/s).  See Figure 8.

Figure 8 – Traveling to an Earth-Crossing Asteroid

If you send astronauts,  then they must have a way home.  Before it is too late (days to weeks),  they must depart the asteroid into an Earth-like orbit,  waiting for the Earth to catch up with them.  Then you might do a free entry,  or you might do a propulsive deceleration into Earth orbit,  to bring them home. 

At the very least this is 17 km/s velocity change required. Maybe over 20 km/s. At present,  we have no rocket vehicles capable of flying this fast.  We will need nuclear propulsion,  or else very huge chemical rockets pushing very small probes and space capsules.

Why humans need to go,  sooner or later:

A robot can only deal with what its programmers anticipated.  It just cannot adapt to the unexpected or the unforeseen,  without direct human intervention.  That is simply just one of the truths of our time. 

Across the distances needed,  it is just not feasible to remotely-operate a probe,  in anything resembling a timely fashion.  Light just does not cross those distances that fast.  Another truth of our time. 

What that really means is this:  sooner or later in the process,  humans simply must go to these asteroids to investigate their real "ground truth" properties. There is just no other way at this time in history to find out "what is" versus "what is not". 

This isn't like going to the moon,  which was a mission about a week,  to at most two weeks,  long.  We are talking about weeks to months in space for the Earth-grazing asteroids.  For the non-Earth-grazing asteroids,  and for most comets,  we are really talking about years in space.  And we just don't know yet how to do that,  without killing our crews.

Bottom line:  we need more capable rockets,  and we need a vehicle for crews that provides artificial gravity and radiation protection. These voyages could range from days to years in duration,  and a small space capsule is only "good" psychologically for a couple of weeks.  These living spaces must be large. 

Conclusions:

There is no better reason for both unmanned,  and manned,  space program efforts than protecting the Earth against asteroid impacts.  The massive extinction event 66 million years ago that extinguished the dinosaurs in favor of the mammals,  is just one example of what damage a 6-10 km size object can do. 

This is not a zero-sum game (despite what politicians insist);  this is something that needs to be ongoing,  at whatever level we think we can afford,  in any given year.  Spend more when you think you can afford more,  simple as that.  But NEVER zero!  Some outcomes are just not tolerable,  no matter how unlikely! 

I recommend the following things be done:

(1) Deploy a constellation of at least 3 asteroid-detection satellites,  using infrared detection devices supplemented by visible and radar,  in orbits about the sun approximately at the orbit of Venus. 

This is just not that expensive a thing to do,  and it will identify the vast bulk of the small (2-6 m) threats to the Earth.  Such would make evacuation of a threatened city possible for the first time.

(2) Develop a means to send unmanned probes,  followed by manned missions,  to several of the Earth-crossing asteroids,  to find out real "ground truth" about their characteristics.  The manned voyages will probably require enhanced propulsion,  possibly nuclear.  Crewed vehicles will be quite large.

The place to test nuclear propulsion safely is on the moon,  where there are no neighbors to annoy,  and where there is no air and water to pollute.  There is no better reason than this, for a return to the moon!  There are other reasons to go back to the moon,  but none are better than for helping to provide protection of the Earth against asteroid threats.

(3) Develop the rockets and the spacecraft needed to send humans to the Earth-crossing asteroids as soon as possible.  This requires both propulsion upgrades,  and it requires built-in protection against space radiation and microgravity disease.  (If you can go there,  you can go to Mars,  or pretty much anywhere else in the inner solar system,  including out to the main asteroid belt.)

What that really means is artificial spin gravity,  and about a meter or more of low molecular weight insulation materials to double as radiation shielding. And plenty of living space for long missions.

These were also my conclusions in 2009 at that meeting.  They have NOT changed since! 

If your elected and appointed officials are not addressing these issues,  you may safely conclude that they are lying to you,  whether by omission or commission.  In any event,  they are not protecting the public safety,  which is their sworn duty.  And that deserves your attention at election times.

Related articles:

4-21-09  On Asteroid Defense and a Good Reason for Having National Space Programs

7-22-09  On the Future of the US Manned Space Program

9-6-09   Space Program Public Support

10-31-09 The Future of NASA Manned Space

3-10-10  About Old "Project Orion" -- the Nuclear Explosion Drive

4-17-10  Space Recommendations

1-21-11  Fundamental Design Criteria for Alternative Space Suit Approaches

8-2-11  What Should the Government's Manned Space Exploration Strategy Be?

5-2-12  Space Travel Radiation Risks

12-31-12  On Long-Term Sustainable Interplanetary Travel

1-5-13  Using Nuclear Rockets Safely for Manned Space Travel

2-15-13  On the Two Dangers From Space Friday 2-15-13

10-2-13  Budget Moon Missions

11-17-13  Rocks From Space

11-17-14  Space Suit and Habitat Atmospheres

1-17-15  Stagnation in Space

4-11-15  Radiation Risks for Mars Trip

1-15-16  Astronaut Facing Drowning Points Out Need for Better Space Suit

2-15-16  Suits and Atmospheres for Space

3-3-16   Effects of Microgravity Demand Artificial Gravity

3-16-18  Suit and Habitat Atmospheres 2018

10-5-18  Space Radiation Risks:  GCR vs SFE

7-14-19  Just Mooning Around