One thing that was surprising (to me, at least) about Missile Defense Agency (MDA) Director Admiral James Syring’s January 19 2016 presentation at the Center for Strategic and International Studies was his description of the MDA’s planned two-stage version of the Ground-Based Interceptor (GBI).
The MDA has long had plans to eventually incorporate a two-stage version of the three-stage GBI currently deployed in Alaska and California into its Ground Based Midcourse GMD) national missile defense system.
The idea of using a two-stage version of the GBI first came to public attention in 2006 when the George W. Bush Administration announced plans to deploy two-stage GBIs in Europe to provide an extra layer of defense of U.S. territory against Iranian ICBMs. Although an agreement was reached in 2008 to deploy ten of the two-stage GBIs on Polish territory, in 2009 President Obama cancelled these plans in order to proceed with his European Phased Adaptive Approach (EPAA). However, the possibility of deploying two-stage GBIs – this time on U.S. territory — was retained was retained as part of the GMD “hedge” strategy.
As part of the GMD hedge, a two stage GBI would increase the GMD system’s battle space by allowing later intercept attempts. The EKV kill vehicle cannot separate from its booster rocket and begin homing in on its target until after the booster burns out, and a two-stage version of the GBI would burn out about seventy seconds earlier than the three-stage version of the GBI.
In June 2010, MDA conducted BVT-01, a non-intercept test of a two-stage version of the GBI (with a CE-I kill vehicle) and classified it as a success. Although the Director of Operational Test and Evaluation subsequently stated that : “A malfunction of the kill vehicle, unrelated to problems associated with FTG-06 above, may have degraded the quality of data collected,” he also stated that: “Data from BVT-01 suggest that the Ground-based Midcourse Defense (GMD) two-stage interceptor could prove a viable boost vehicle in addition to the currently deployed three-stage interceptor.”
A two-stage version of the GBI could be deployed beginning in about 2020 as part of a new C3 booster configuration that would include an option for a two-stage version. As of early 2015, plans called for a non-intercept test of the two-stage booster in the third quarter of FY 2018 with an intercept test following in the third quarter of FY 2019.
So what was surprising about Admiral’s Syring description of the two-stage GBI? Previous public analyses of the two-stage GBI (in the context of the proposed European Deployment) had assumed that it would be produced by physically removing the third, smallest stage of the GBI booster, so that only the first two stages remained. This approach would be consistent with the fact that the two-stage GBI was to have exactly the same length as the three-stage GBI, since the three-stage missile shroud (nose cone) covered both the kill vehicle and the entire third stage so that removing the third stage while retaining the original shroud would not change the missile’s length.
However, Admiral Syring’s presentation made it clear that the two-stage GBI would in fact be a three-stage missile in which one of the stages simply would not be used. According to my transcription of the video of part of his talk, Admiral Syring stated that the two-stage GBI is:
“…not a different design from a booster standpoint. It’s going to be done through software and the warfighter will be able to choose between a two-stage and a three-stage in terms of does it – does it – fly the two-stage or does it – second stage – or does it just drop.”
Thus all of the GBIs deployed in silos will actually have three stages, but at least some of the future ones will be configured so that the GMD command system has an option not to ignite one of the stages, instead simply dropping it off. Moreover, the quote also suggests that the unused stage might be the second rather than the third stage (although that might be reading too much into a verbal quote).
Further, one of Admiral Syring’s slides (Figure 1 below) shows that a planned 2020 GMD intercept test will use a “2/3 Stage Selectable GBI.”
Figure 1. Screen capture from the CSIS video of Admiral Syring’s presentation. (The CSPAN video has the full caption under each image, but the images are lower resolution.)
This approach to achieving a two-stage booster by simply not firing one stage of a three-stage booster results in an interceptor burnout speed that is significantly lower than that would be obtained if the unused booster stage was physically removed from the interceptor before it was deployed because the unused stage is now simply dead weight. However, in the late-intercept, battle space-extending role the two-stage GBI is intended for, the burnout speed is less important than the boost time. Thus this seeming wasteful (of a missile stage) approach might be attractive if it reduced costs by minimizing the design and testing work relative to producing a true two-stage interceptor, and it would also avoid having to decide how to allocate future deployments of GBI’s between the two and three-stage versions.
One issue this approach to producing a two-stage interceptor capability might resolve is whether or not the proposed but now cancelled two-stage interceptors in Poland would have been physically capable of intercepting any Russian ICBMs. Outside analysts consistently assumed that two-stage GBIs would be produced by removing the third stages, and found that the resulting missiles would fast enough to catch up with at least some Russian ICBMs fired at U.S. territory. On the other hand, the MDA insisted, as shown in Figure 2 below, that the two-stage interceptors were too slow to even come close to catching up with any Russian ICBMs.
Figure 2. MDA slide from 2007 showing that the proposed two-stage GBI interceptors in Poland cannot catch up with Russian ICBMs fired at the U.S. East Coast.
Going back through the debate on this issue, I can’t find any statement from MDA regarding how the two-stage booster was to be configured. If, however, the two-stage booster for the proposed European Defense was to have been produced in the same way as those proposed for deployment beginning in 2020, that is by simply not igniting one of stages of a three stage GBI, than the resulting missile would be much slower than the outside analysts calculated, possibly explaining the discrepancy between their and MDA’s results. Slide 3 below, from 2008, may hint at this possibility, saying that the outside analysts had “optimistic assumptions in mass properties and propulsion” and that their models’ results “exceeds the thermal and structural limitations of the GBI.” (Removing the third stage would lead to significantly higher accelerations, particularly during the second-stage burn.) If this was the case, one can see why MDA may not have wanted to clarify the issue, since the Russians would almost certainly be even unhappier with the proposed deployment in Poland if it turned out the two-stage interceptors actually had three stages.
Figure 3: MDA slide with arguments about why the two-stage GBI is Poland could not intercept Russian ICBMs.
 Vice Admiral James D. Syring, “Ballistic Missile Defense Update,” Presentation at the Center for Strategic and International Studies, January 19, 2016. Video of the presentation are available at http://csis.org/event/ballistic-missile-defense-system-update-0 and http://www.c-span.org/video/?403405-1/discussion-ballistic-missile-defense. (The two videos differ somewhat in their coverage of the Admiral’s slides.)
 U.S. Department of Defense, Ballistic Missile Defense Review, February 2010, p. 17. Available at: http://www.defense.gov/Portals/1/features/defenseReviews/BMDR/BMDR_as_of_26JAN10_0630_for_web.pdf.
 Director of Operational Test & Evaluation, “Ground-Based Midcourse Defense (GMD” in 2010 Annual Report, pp. 233-234. Available at: http://www.dote.osd.mil/pub/reports/FY2010/pdf/bmds/2010gmd.pdf.
 Scott Maucione, “MDA Puts $51 Million Into Budget To Develop Two-Stage GBI Booster,” Inside Missile Defense, March 18, 2015.
 Theodore A. Postol, “Why US National Intelligence Estimates Predict that the European Missile Defense System Will Fail: Technological Issues Relevant to Policy,” Slides from lecture to German Physical Society, Berlin, February 29, 2008. Available at: http://thebulletin.org/sites/default/files_legacy_files/20080430_Postol.pdf; U.S. Congressional Budget Office. “Options for Deploying Missile Defenses in Europe,” February 2009. Available at: https://www.cbo.gov/sites/default/files/111th-congress-2009-2010/reports/02-27-missiledefense.pdf. The CBO study was based only on publicly available information. While Figure 3-11 of the CBO report appears to show that the two-stage GBIs in Poland cannot cover any U.S. territory from Russian ICBMs, that Figure assumes a 3.0 km/s minimum collision speed difference at the intercept. As shown in Figure 3-12, if this requirement is instead set at 1 km/s (2,200 mph), then the entire eastern half of the United States can be covered.
 Slide from MDA Executive Director Patricia Sanders, “Missile Defense Program Overview For The 4th International Conference on Missile Defense,” June 26, 2007. Available at: https://mostlymissiledefense.files.wordpress.com/2013/06/bmd-overview-sanders-june2007.pdf.
 Slide from: MDA Director Lt. Gen. Trey Obering, “Ballistic Missile Defense Program Overview For The National Defense Industrial Association,” May 8, 2008. Available at: https://www.ndia.org/Divisions/Divisions/MissileDefense/Documents/Content/ContentGroups/Divisions1/Missile_Defense/NDIA.pdf.