U.S. Conventional Prompt Global Strike Issues for 2008 and Beyond (2008) / Chapter Skim
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Appendix G: The Why and How of Boost-Glide Systems
Appendix G: The Why and How of Boost-Glide Systems
Pages 206-215
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From page 206... ...
, or "lifting body" without propulsion, can be used to extend the range of a ballistic-missile payload beyond the purely ballistic range. It can also be used for out-of-plane or "dogleg" maneuvers to avoid overflight of certain areas or to allow the dropping of initial rocket stages into the sea or into another body of water not under the ballistic path.
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From page 207... ...
But it does, and in principle the RV could be designed as a lifting body for the hypersonic regime, and if the thermal insult could be managed it could transition in the upper regions of the atmosphere to near-horizontal flight, and then use lift and change of altitude, air density, and change of angle of attack to support the RV weight for a substantial range extension beyond the purely ballistic trajectory. This approach was validated decades ago by flights of the Mk-500 "Evader" RV.
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From page 208... ...
FLAT EARTH 1. On a flat Earth, the maximum ballistic range is achieved with a constant launch angle of 45º to the horizontal; the purely ballistic range is Rb = V2/g, as is readily derived.
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From page 209... ...
The glide portion of the trajectory, Rb, is thus reduced to 49 percent of what it would have been had the projectile been fired horizontally in the first place into glide mode at V = Vi and at constant L/D = 2.2. The ballistic-trajectory range extension is thus 53.9 percent of the ballistic range, rather than the 110 percent if the vehicle could have negotiated the –45º pull-up without velocity loss on a flat Earth or at short range, as would be the case in principle if a long tether could have been used to supply the centripetal force for the maneuver.
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From page 210... ...
Figure G.1, bitmapped, uneditable, color FIGURE G-2 Normalized velocity versus range (Columns C versus E of Table G-1) for pure glide.
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From page 211... ...
Figure G.3, bitmapped, uneditable, b&w FIGURE G-4 Velocity versus time for pure glide (Columns C versus B of Table G-1)
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From page 212... ...
, "Velocity versus time for pure glide," for cases in which time is of interest. The spreadsheet, of which excerpts are shown in Table G-1, embodies calculation results using the following formulas: beginning at rest, dV/dt = g D/L; at high speeds and constant altitude, aerodynamic lift does not need to compensate g -- only g × (1 – (V/Ve)
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From page 213... ...
TABLE G-1 Excerpts of Calculation Results from Spreadsheet NOTE: Columns A, C, and D are normalized to 7.90 km/s. Columns G and I are km/s2 and km/s.
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From page 214... ...
One can interpolate for an initial glide speed of 6.5 km/s to find a glide range of about 7,900 km -- again in reasonable agreement with the result of the detailed calculation as displayed in Figure G-1. Note that entry into glide flight horizontally at 7 km/s, rather than at –10º, would provide a glide range of 10,740 km; most of the increase arises from the closer approach to orbital speed of 7.90 km/s, with the resultant reduction in needed aerodynamic lift and hence drag.� Some of the proposals for long-range boost-glide vehicles enter the glide phase at angles from the horizontal two to four times smaller than the 10º example used here, and at speeds considerably closer to orbital speed of 7.90 km/s (25,920 ft/s)
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From page 215... ...
The intense heating of the BGV during the whole of the glide phase provides a strong infrared signal to defensive systems equipped to detect it or to use it for an infrared homing intercept. A simple terminal maneuver for a ballistic missile will allow it to deny sanctuary to structures and locations shielded by a near-vertical bluff.
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