Now We Can Start to Defend Planet Earth

By: Peter Garretson

Excerpt: New research indicates we have the ability to protect the US from asteroid strikes. The question is, who will take the responsibility of defending the US from asteroids?

Approximate Reading Time: 3 Minutes

For decades we have known that the most likely asteroid threat is the small asteroids like the Chelyabinsk or Tunguska events that penetrate low enough to cause a ground burst and damage or destroy cities. We thought that we were helpless against such threats because they are too small and dim to find in advance—far, far harder to optically detect than civilization destroying asteroids; previous studies showed that fragmenting larger asteroids might make the problem worse. But a recent study by Aerospace Corp overturns these dated ideas and shows that a relatively modest system could protect all of CONUS.

OTH, multi-domain, emerging security environment

The study says that small asteroids (15-30m in diameter) could be disrupted with a kinetic impactor that would shatter them at an altitude high enough (100-2,700km) that no individual fragment could penetrate low enough to create a ground-burst. Because of the extremely high closure velocities, a kill vehicle as small as 100kg packs the sufficient “minimum energy needed for disruption” for a 20m asteroid.

Further, the study says that only a single interceptor site would be required to cover the entire CONUS. This site would require 3-stage interceptors with sufficient energy (7km/sec) to overcome gravity and drag losses and deliver the necessary “interceptor would resemble a tactical missile more than a space launch vehicle.”

Finally, the study says that the radar cross section of a 15-30m asteroid is large enough that existing phased array radars could detect this class of asteroids at an altitude of 20,000-30,000 km. Detections above 20,000km provide sufficient timeline (~11 minutes) for tracking and multiple launch opportunities, and minimum detection at 15,000km ensures at least one engagement for 99% of asteroid trajectories. Moreover, only 3 radar faces would detect 97% of this class of asteroid threats.

So, there it is: we can use existing missile defense technologies to protect the CONUS from 15-30m asteroid threats. Now who wants the mission to defend America from asteroids?

Before being dissolved following the 9/11 force restructuring, USSPACECOM created at CONOPS for asteroid defense, and had proposed this as a requirement to the Joint Requirements Oversight Council (JROC). But who is the champion today? Who feels the responsibility to develop an Initial Capability Document (ICD) for the JROC to defend America from small asteroid threats?

Several organizations could make a case. Generally, when we think about defending the homeland from an external, city-killer class threat, we think of USSTRATCOM, and its subsidiaries, Missile Defense Agency (MDA) / Joint Functional Component for Integrated Missile Defense (JFCC IMD), the Defense Threat Reduction Agency (DTRA), and Joint Force Space Component Commander (JFSCC). We might also think of NORAD, the Department of Homeland Security or the Federal Emergency Management Agency. Another entity is Army Air Defense that generally operate this class of ground-based interceptors. Others think this is for a new agency.

Of course, I hope it will be my service, the US Air Force, that displays the “jealous advocacy” for this exciting mission, since (through AFSPC), the USAF is charged with providing Space Situational Awareness, Launch and Space Control in support of Homeland Security and Homeland Defense.


Lt Col Peter Garretson is an Instructor in the Schriever Scholars Space Concentration at Air University’s Air Command and Staff College (ACSC), and lead for the Air University Space Horizons Research Group, which seeks to “Re-imagine Spacepower in the Age of Asteroid Mining.” He has been a strategy and policy advisor to the Chief of Staff of the Air Force on Space and Great Power conflict in Asia. He is the former Chief of USAF Future Technology, and has served at the Defense Advanced Projects Agency (DARPA) as a Service Chief Fellow, and a Los Alamos National Laboratory as an Academy Research Associate. He was the first serving military officer to be detailed as a visiting fellow to Asia’s #1 think tank, the Ministry of Defense Funded Institute for Defense Studies and Analysis (IDSA) in New Delhi, India. Lt Col Garretson has over 50 publications including on the topics of space governance, space policy, space based solar power, asteroid mining, planetary defense, strategic culture, and US military strategy and security cooperation in Asia.


Disclaimer: The views expressed are those of the author and do not necessarily reflect the official policy or position of the Department of Defense or the U.S. Government


Print Friendly, PDF & Email

3 thoughts on “Now We Can Start to Defend Planet Earth

Leave a Reply to ferahtia_FS Cancel reply