Editing Asteroid impact avoidance (section)

====Surface and subsurface use====
[[File:Asteroid Capture.jpg|thumb|This early [[Asteroid Redirect Mission]] artist's impression is suggestive of another method of changing a large threatening celestial body's orbit by [[asteroid capture|capturing]] relatively smaller celestial objects and using those, and not the usually proposed small bits of spacecraft, as the means of creating a powerful [[kinetic energy|kinetic impact]],<ref>{{cite journal|last1=Asphaug|first1=E.|last2=Ostro|first2=S. J.|last3=Hudson|first3=R. S.|last4=Scheeres|first4=D. J.|last5=Benz|first5=W.|date=1998|title=Disruption of kilometre-sized asteroids by energetic collisions|journal=Nature|volume=393|issue=6684|pages=437–440|url=http://trs-new.jpl.nasa.gov/dspace/bitstream/2014/19541/1/98-0965.pdf|url-status=dead|archive-url=https://web.archive.org/web/20160306071546/http://trs-new.jpl.nasa.gov/dspace/bitstream/2014/19541/1/98-0965.pdf|archive-date=March 6, 2016|doi=10.1038/30911|bibcode=1998Natur.393..437A|s2cid=4328861}}</ref> or alternatively, a stronger faster acting [[gravitational tractor]], as some low-density asteroids such as [[253 Mathilde]] can [[crumple zone|dissipate impact energy]].]]

In 2011, the director of the Asteroid Deflection Research Center at [[Iowa State University]], Dr. Bong Wie (who had published kinetic impactor deflection studies<ref name="spacesailing.net"/> previously), began to study strategies that could deal with {{convert|50|to(-)|500|m|ft|adj=mid|-diameter|-2|sp=us}} objects when the time to Earth impact was less than one year. He concluded that to provide the required energy, a nuclear explosion or other event that could deliver the same power, are the only methods that can work against a very large asteroid within these time constraints.

This work resulted in the creation of a conceptual [[Hypervelocity Asteroid Intercept Vehicle]] (HAIV), which combines a [[Deep Impact (spacecraft)|kinetic impactor]] to create an initial [[Impact crater|crater]] for a follow-up subsurface nuclear detonation within that initial crater, which would generate a high degree of efficiency in the conversion of the nuclear energy that is released in the detonation into propulsion energy to the asteroid.<ref>{{cite web|url=http://www.space.com/21333-asteroid-nuke-spacecraft-mission.html |title=Nuking Dangerous Asteroids Might be the Best Protection, Expert Says |website=[[Space.com]] |date=29 May 2013 |access-date=2013-07-02 |url-status=live |archive-url=https://web.archive.org/web/20160401213420/http://www.space.com/21333-asteroid-nuke-spacecraft-mission.html |archive-date=2016-04-01 }} Nuking Dangerous Asteroids Might Be the Best Protection, Expert Says. Includes a supercomputer simulation video provided by [[Los Alamos National Laboratory]].</ref>

A similar proposal would use a surface-detonating nuclear device in place of the kinetic impactor to create the initial crater, then using the crater as a [[rocket nozzle]] to channel succeeding nuclear detonations.

Wie claimed the computer models he worked on showed the possibility for a {{convert|300|m|ft|adj=mid|-wide|abbr=off|sp=us}} asteroid to be destroyed using a single HAIV with a warning time of 30 days. Additionally, the models showed that less than 0.1% of debris from the asteroid would reach Earth's surface.<ref>{{Cite web |author1=Mike Wall |date=2014-02-14 |title=How Nuclear Bombs Could Save Earth from Killer Asteroids |url=https://www.space.com/24696-asteroid-strike-nuclear-bombs.html |access-date=2023-04-25 |website=Space.com |language=en}}</ref> There have been few substantial updates from Wie and his team since 2014 regarding the research.

As of 2015, Wie has collaborated with the Danish [[Emergency Asteroid Defence Project]] (EADP), which intends to [[crowdsource]] sufficient funds to design, build, and store a non-nuclear HAIV spacecraft as planetary insurance. For threatening asteroids too large or close to Earth impact to effectively be deflected by the non-nuclear HAIV approach, nuclear explosive devices (with 5% of the explosive yield than those used for the stand-off strategy) are intended to be used, under international oversight, when conditions arise that necessitate it.<ref>{{Cite web|url=http://asteroiddefence.com/|title=EADP|date=May 5, 2015|archive-url=https://web.archive.org/web/20150505181554/http://asteroiddefence.com/ |archive-date=2015-05-05 }}</ref>

A study published in 2020 pointed out that a non-nuclear kinetic impact becomes less effective the larger and closer the asteroid. However, researchers ran a model that suggested a nuclear detonation near the surface of an asteroid designed to cover one side of the asteroid with x-rays would be effective. When the x-rays cover one side of an asteroid in the program, the energy would propel the asteroid in a preferred direction.<ref>{{Cite journal |last1=Dearborn |first1=David S. P. |last2=Bruck Syal |first2=Megan |last3=Barbee |first3=Brent W. |last4=Gisler |first4=Galen |last5=Greenaugh |first5=Kevin |last6=Howley |first6=Kirsten M. |last7=Leung |first7=Ronald |last8=Lyzhoft |first8=Joshua |last9=Miller |first9=Paul L. |last10=Nuth |first10=Joseph A. |last11=Plesko |first11=Catherine S. |last12=Seery |first12=Bernard D. |last13=Wasem |first13=Joseph V. |last14=Weaver |first14=Robert P. |last15=Zebenay |first15=Melak |date=2020-01-01 |title=Options and uncertainties in planetary defense: Impulse-dependent response and the physical properties of asteroids |journal=Acta Astronautica |language=en |volume=166 |pages=290–305 |doi=10.1016/j.actaastro.2019.10.026 |bibcode=2020AcAau.166..290D |s2cid=208840044 |issn=0094-5765|doi-access=free }}</ref> The lead researcher with the study, Dave Dearborn, said a nuclear impact offered more flexibility than a non-nuclear approach, as the energy output can be adjusted specifically to the asteroid's size and location.<ref>{{Cite web |title=Nuclear impulse could deflect massive asteroid |url=https://www.llnl.gov/news/nuclear-impulse-could-deflect-massive-asteroid |access-date=2023-04-25 |website=Lawrence Livermore National Laboratory |language=en}}</ref>