Ian33 said:
Did they not come to the decision that to survive, the B-2B had to be a very capable low level airframe? Hence the extra weddges at the rear and that beaver tail?
From "B-2 Systems Engineering Case Study":
> The evaluation of the contractors’ proposals proceeded on site at the contractors’ facilities throughout December 1980, through January and into February 1981. The Source Selection Advisory Council (SSAC) received regular briefings on the progress of the evaluation and the outcome of the ongoing survivability assessment. The SSAC concluded that growth provisions for low altitude capability would be a prudent hedge against an ever-changing and maturing radar threat operational throughout the Soviet Union.
At the time, this was not actually based on a Red Team assessment but on (speculative) intelligence estimates. The thinking here was that the if the Soviets developed a counter to the B-2 at high altitude it could be shifted to low altitude.
tacitblue said:
It's precisely for trigonometry that you want to go low, especially when releasing cruise missiles as opposed to gravity bombs. (obviously not all land is created equal)
From "Route Planning Issues for Low Observable Aircraft and Cruise Missiles":
> In some high, overlapping threat environments, the effects of background clutter and propagation phenomena (such as multipath and ducting) on the performance of acquisition radars may also be important in route planning low- altitude, terrain-following LO platforms. For example, without taking into consideration background clutter, the threat penetration analysis for a well-
defended target, located in a narrow valley, may show that there are no low-risk routes into the target.
> Obviously, to deternine the effects of background clutier and propagation phenomena on route planning, operators must be provided with !he necessary
data, to create clutter and refl;ectivity maps, and with the appropriate threat penetration models. However, because of difficulties in creating high delily clutter and refiectivity maps, variabilities in background clutter and reflectivity (generic models may not suffice), time constraiints (extensive computations are required), and the desire to be offense conservative, most route planning procedures assumne no, background clutter or propogation effects on enemay defenses
Lincoln Laboratory and the DoD Red Team studied this to death from the late 1970s through the 1990s. This is why the AGM-129 did not penetrate at low level - low level was reserved for the run in to the target primarily because of terminal guidance needs. It was also not released at low altitude.
Low altitude penetration:
1. Puts the aircraft much closer to the threat.
2. Gives the threat more favorable viewing aspects.
3. Increases the effects of terrain, etc. reflections. This drastically reduces the effects of low observable design.
4. Makes route planning much, much more difficult and requires very precise emitter information and modeling.
5. Changes the enemy kill chain significantly. AAA and airborne intercept are more of a concern, RF SAMs less so.
These concerns (and more) were raised by USAF during their assessments of the A-12 program as well.
