USAF Boosting Its Spirits
by Brendan P. Rivers
Sep. 20, 2004
US Air Force (USAF) B-2 Spirit stealth bombers are currently undergoing a number of upgrades to improve their stealth, communications, radar, and weapons capabilities – enhancements that are just now coming to the aircraft after about 10 years of operational service.
B-2 bombers are currently receiving new low-observable (LO) coatings under the Advanced High-Frequency Material (AHFM) program that not only improve the aircraft's stealth capabilities but also make the aircraft much easier to maintain. Northrop Grumman Integrated Systems (Palmdale, CA), prime contractor for the B-2 program, has developed not only new LO coatings for the bomber but a new application method as well, one that employs a robotic spray mechanism that is accurate to millionths of inches.
In addition, the company developed new LO fasteners for the outer panels of the aircraft that make it much easier for maintenance personnel to access systems inside the aircraft, fasteners that make removing the panels much the same as taking them off of regular, non-stealthy aircraft. Not all of the outer panels will be fastened together in this manner, and there will still be some of the tape currently used to hold them in place. However, according to Henry Heimpel, manager of government relations for Northrop Grumman, tape will still be used in places where the panels are not frequently removed to access systems for maintenance. Although Heimpel said that the new LO coatings would also increase performance he declined to be more specific.
Application of the new LO coatings will take a total of seven years to complete on the USAF's B-2 fleet of 21 aircraft, as the LO upgrade will be performed during the aircrafts' regular depot-level maintenance cycle (in fact, the only maintenance performed on the aircraft at the depot level is on its LO coatings, which Heimpel attributed to the high reliability of the aircraft itself). One aircraft with the new coating has been delivered to the Air Force and another has just been completed. Northrop Grumman plans to complete another by the end of the year. Performing the LO upgrade during the regular depot-level maintenance rotation, however, means that the company will only be able to apply the new coating to three B-2s each year. Heimpel noted that this is "the dilemma of having such a small fleet." Only so many B-2s can be rotated through the depot at one time due to the service's operational and training needs.
In addition to the new LO coatings, the B-2 Spirits are receiving a new UHF communications system and, by the end of the decade, will also be connected to the new Advanced Extremely High Frequency (AEHF) satellite-communications (SATCOM) system, which will replace the current MILSTAR SATCOM system. Alongside the communications enhancements, the B-2's computers and processors will be upgraded as well, a move necessitated by rapidly evolving technology. As Heimpel put it, if you look at the B-2 now, "it's like a room full of Commodore computers," as design work on the aircraft began back in the 1980s.
The B-2's AN/APG-181 Ku-band radar will also be upgraded by replacing the legacy antenna with a new solid-state, active electronically scanned array (AESA), which will be provided by Raytheon (El Segundo, CA) under a deal announced on Sept. 9 that could be worth as much as $600 million. This represents the fourth phase of the B-2 Radar Modernization Program (RMP). Under the RMP, each B-2 will receive two new AESA antennas, one each on either side of the nose on the underside of the aircraft.
Of course, putting a high-power antenna on a stealth aircraft seems like it would be counter-productive: how can the aircraft be stealthy when its active, high-power radar is practically screaming out its location? The answer, according to Rob Dorr, Northrop Grumman's B-2 RMP program manager, is that the antenna will incorporate some LO design features, but perhaps more important, the radar will employ low-probability-of-intercept (LPI) waveforms and power-management techniques (the latter presumably meaning that the B-2 would employ the radar very conservatively).
Interestingly, the radar's performance, according to Dorr, will not be enhanced under this program – by Air Force requirements. The program, as currently structured, requires no enhancement of capability, but for the radar to operate in another location in the electromagnetic spectrum, although the potential for future capability upgrades remains. The real driver for the upgrade, the need to operate in another portion of the electromagnetic spectrum, was necessitated by a move made late in US President Bill Clinton's administration. The legacy system operates in a portion of the electromagnetic spectrum where Department of Defense (DoD) systems are secondary users, with commercial applications as primary users. As a secondary user, the B-2 radar could continue operations only if the system did not interfere with primary users, as interference could lead to the radar unintentionally "frying satellites," according to one industry source.
In 2000 a US Department of Commerce letter to the director of spectrum management for the DoD stated that secondary users in the portion of the electromagnetic spectrum where the B-2 radar operates would no longer be able to operate on a non-interference basis with primary users in the near future. This correspondence drove the USAF to migrate the B-2 radar system to another portion of the electromagnetic spectrum in which DoD systems are guaranteed primary-user status.
But while the radar upgrade may not yet be providing the B-2 with a boost in capabilities, the same cannot be said about enhancements being made to the bomber's ability to deliver ordnance. Currently, the B-2 is able to deliver a total of 16 Joint Direct Attack Munitions (JDAMs), but Northrop Grumman is about to deliver a new bomb rack to the Air Force that would enable the stealth bomber to deliver 80 JDAMs – meaning that a single B-2 could strike as many targets as five could using the legacy bomb rack (or one B-2 conducting five separate sorties).
Moreover, with the new bomb rack, the B-2 will be able to launch all 80 in rapid succession, to 80 different targets, if desired, and the target of any individual JDAM can be changed in flight by the aircrew. The modified bomb racks have been certified by the Air Force and have completed developmental testing. Northrop Grumman will modify the bomb racks of four B-2s by the end of this year and plans to modify the remainder of the fleet thusly by the end of 2006.
In terms of future upgrades, work will begin in March 2005 on equipping the B-2 with the Enhanced JDAM, which has a penetrator warhead. Interestingly, sources indicate that the Air Force is also looking at developing a warhead weighing in the neighborhood of 20,000-25,000 lbs. Should the service move forward with the development of such a weapon, Northrop Grumman officials said they believe the B-2 would be ideal for delivering it, as it would be able to carry one under each wing. Northrop Grumman has also been pitching a plan to the Air Force that would see the B-2 carry Small Diameter Bombs (SDBs). Heimpel said that the stealth bomber could carry a total of 200-240 SDBs.
In addition, the USAF is also considering finally putting the third crew station to use (currently only two of the aircraft's three crew stations are used). Heimpel noted that if the aircraft ever did carry SDBs, "it might be good to have a third guy." The third crew station could also be used to expand the missions the B-2 can perform, added Kenny Linn, director of business strategy and development for Northrop Grumman. One such mission, Linn said, might be close-air support for special-operations forces.