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B-2 Spirit1

Payload
40,000 pounds (18,144 kilograms)
Wingspan
172 feet (52.12 meters)
Weight
160,000 pounds (72,575 kilograms)
Maximum takeoff weight
336,500 pounds (152,634 kilograms)
Range
approximately 6,000 nautical miles (9,600 kilometers)

B-52 Stratofortress2

Payload
70,000 pounds (31,500 kilograms)
Wingspan
185 feet (56.4 meters)
Weight
Approximately 185,000 pounds (83,250 kilograms)
Maximum takeoff weight
488,000 pounds (219,600 kilograms)
Range
8,800 miles (7,652 nautical miles)

B-1B Lancer3,4

Payload
75,000 pounds (34,019 kilograms)
Wingspan
137 feet (41.8 meters) extended forward, 79 feet (24.1 meters) swept aft
Weight
approximately 190,000 pounds (86,183 kilograms)
Maximum Takeoff Weight
477,000 pounds (216,634 kilograms)
Range
5,100 nmi (5,900 mi; 9,400 km)

The US Air Force web-site says:

The revolutionary blending of low-observable technologies with high aerodynamic efficiency and large payload gives the B-2 important advantages over existing bombers.

But in comparison with the other bombers, including much older B-52, it appears to be less aerodynamically efficient and carries less payload.

Why does the B-2 carry a much smaller payload than the other bombers of comparable size? Does it signify, that B-2 has worse aerodynamic characteristics? If yes - what are causes of it?

Rodrigo de Azevedo
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Gill Bates
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4 Answers4

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The simple answer is that it is optimized for being low observable/stealthy, and long range, rather than for maximum payload.

When you design an aircraft, you make a variety of trade offs depending upon which features are most important for that design. The design of the B-2, which reaches back into the 1980's1, put a premium on the ability to avoid being detected by radar. This informed the shape. The USAF's strategic purpose for that aircraft was to enable it to reach globally, so that it could be launched form the continental US or a forward deployed base. This put a premium on range/fuel capacity.

@Durandal points to another detail/difference: The B52 and B1 both can carry ordnance on external hard points (and this is a must to get up to the cited payloads). The B2 has no such hard points because it would nullify its stealth capability. There is simply no room to put more munitions within the bomb bay.

With the advent of precision weapons, which were in parallel development to the B-2, the raw tonnage wasn't as important as getting to the target area, and getting out "without being seen."

Because aircraft are all constrained somewhat by the cube/square law in terms of size, the trade offs/compromises on that model arrived at a payload that fit in with the rest of the requirements.

Both the B-52 and B-1 were build under a different design paradigm, under different requirements combinations, and were "pre-stealth" bombers: the B-52 was meant to get the most range and raw payload together, while the B-1 combined speed (supersonic, back when speed was perceived to be at a premium) and payload foremost. While both have since benefitted from the use of precision munitions, the original designs (all nuclear weapons carriage considered) had to account for the problem of non-precision munitions shortcomings with accuracy. (Experiences in WW II informed this problem, as did experience in Viet Nam). You need to drop a pattern of "x many bombs" to have a high probability of hitting a given target.

1 Insofar as the "flying wing" idea for the shape of the B-2, the initial attempts in that direction go back to the 1930's and the Ho_229 as so @paracetamol kindly reminds us. Also, and FWIW, it is related to a DARPA project that goes back to the 1970's (stealth / radar resistant in general) that was compromised publicly by President Carter during a press conference. Actually, those paying attention had heard of it from Kelly Johnson: In fact, that existence was far from secret. On July 23, 1976, readers of Aerospace Daily were informed that Clarence L. (Kelly) Johnson, "the nation's premier aircraft designer" and architect of the U-2 and SR-71 spy planes, was bulding "a new 12,000-pound, one-man Stealth aircraft" at the Lockheed plant in Burbank, Calif. The magazine claimed that the $90 million program, sponsored by the Defense Advanced Research Projects Agency, was designed "to reduce aircraft visibility -- optical, acoustic, and radar signatures -- through new technology."

KorvinStarmast
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    "The design of the B-2, which reaches back into the 80's, put a premium on the ability to avoid being detected by radar." That "design" however, was developed as far back as the 30's [https://en.wikipedia.org/wiki/Horten_Ho_229] ;) – paracetamol Jun 26 '17 at 17:29
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    @paracetamol while that hasn't as much to do with the final B-2 stealth, range, and payload decisions, "Flying wing" as a concept ... good point. I'll add that. :-) – KorvinStarmast Jun 26 '17 at 17:39
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    There is a missed aspect. The B52 and B1 both can carry ordonance on external hardpoints (and this is a must to get up to the cited payloads). The B2 has no such hardpoints because it would nullify its stealth capability. The plane itself could most likely carry larger payloads, but there is simply no room to put more munitions within the bomb bay. Both B1 and B52 have been upgraded to carry an assortment of contemporary guided munitions (or in case of the B1 cruise missiles were among its initial capability already). – Durandal Jun 26 '17 at 17:56
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    @Durandal Fair point, and F-35 is running into similar challenges though I recall that it has provision for external stores. I paraphrased your point, and credit to you. Thank you. – KorvinStarmast Jun 26 '17 at 18:03
  • Look at B-2 max. takeoff weight. It is much smaller then of the other bombers. – Gill Bates Jun 27 '17 at 16:48
  • @GillBates And your point is? I refer you to the cube/square law yet again. Aircraft design takes a great many things into account. Suggest you do some research and find out if you can what the minimum acceptable pay load was for the requirement to which the design was adapted. Since you have chosen to believe that a single metric, payload, is somehow the driver to this design, I am not sure what further help any of us can be for you. – KorvinStarmast Jun 27 '17 at 18:21
  • @KorvinStarmast, 1 - This is a bomber, so it's reasonable to assume, that payload size matter for it. 2 - The USAF and Northrop Grumman pages states, that payload is the key advantage of the aircraft. 3 - The USAF page also says, that aerodynamic efficiency is the key advantage of B-2. – Gill Bates Jun 28 '17 at 06:51
  • @GillBates You are mixing apples and oranges; it's payload size is informed by the aerodynamic properties of the flying wing and range; your juxtaposition with B-1 and B-2 is in a lot of ways a non sequitur. Not built with identical mission requirements. (And sadly, they curtailed the buy thanks to the Clinton era austerity. The production run was supposed to be quite a bit larger originally) – KorvinStarmast Jun 28 '17 at 11:44
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The B-1 and B-52 were introduced at a time when most bombs were not guided. Thus, the mission for these older bombers required larger payloads to deliver large quantities of "dumb" bombs to blanket the target area. The B-2 was introduced in 1997, at a time when guided smart bombs were being used more frequently. The B-2 carries fewer, but much more accurate (guided) weapon systems.

Devil07
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For several reasons:

  • Philosophy of Use: the B-2 was designed from the drawing board upward to be a nuclear bomber to specifically used for penetration of dense Integrated Air Defense Systems (IADS) to strike specific high value Command, Communications, and Intelligence (C3I) and nuclear forces, primarily the threat posed by Soviet mobile ICBMs. This left large conventional warloads as as a secondary mission only. The design requirement were changed halfway through the program to provide for low to medium altitude penetration of a target due to reservations amongst the Air Force leadership on the effectiveness of stealth at that time, altering the size and payload requirements of the aircraft.

  • The Politics of Stealth: During the 1970s and early 80s when Low Observable Technology (LOT) was in its infancy, the military leadership did not fully understand its potential or the effect it would have on future air warfare. Instead it saw the technology and envisioned stealth aircraft as a sort of Delta Force type weapon; the USAF would maintain a select few - and highly classified - squadrons of stealth aircraft to strike specific high value C3I targets, blinding the enemy while he was rushed by large and overwhelming conventional strike aircraft. As such, stealth aircraft were not going to require the carriage of a lot of munitions for the task; this was more clearly seen in Lockheed's Senior Trend project, the airplane which became the F-117 Nighthawk, which only carried two large bombs for a payload. The philosophy can't be argued too much with; we decimated the Iraqi military with a similar strategy in 1991 during Operation Desert Storm. But it ignores the reality of air warfare today where non stealth aircraft simply aren't survivable in an advanced IADS environment.

  • Smaller Bombers: At the time of Senior Peg/Senior Ice, the USAF Strategic Air Command (SAC) had begun a shift in philosophy from large intercontinental bombers toward smaller fighter bombers such as the FB-111 for its nuclear delivery needs. The strategy had several advantages to it. Smaller bomber were much cheaper and could be procured in larger numbers for a given defense budget. Second, they were cheaper to operate and maintain, and thus could log more flight time and have better mission readiness than their larger counterparts. Third a large force of smaller bombers was more resilient to enemy defenses, if only by means of attrition. This design philosophy is very apparent in Lockheed's Senior Ice proposal and possibly had considerable influence within Northrop on its Senior Peg ATB proposal, which became the B-2.

Romeo_4808N
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There is another possibility - Neither the B52 nor the B1 has had information on it restricted to the degree that the B2 has.

It may well be that the B2's actual payload is quite a bit higher than has been publicly acknowledged. A great deal about that aircraft is still considered highly classified.

tj1000
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    We know (or can reasonably estimate) the size of its bomb bay, though. Unless it's hiding another super-duper top-secret one elsewhere in the airframe, decent conclusions can be made on its capacity versus something like the B-52. – ceejayoz Jun 26 '17 at 19:25
  • No, you have only seen what has been deemed acceptable for public release. There are numerous examples of military items whose true capabilities have been kept secret long after the item itself was shown in public, as a potential unpleasant surprise for an adversary. For decades after its launch, the true top speed of the passenger liner/potential troop ship SS United States, around 45 knots, was kept secret, as a surprise for a potential USSR invasion into Europe. To this day, the top speed of a LA class submarine, or the maximum diving depth of an Ohio SSBN are still kept secret. – tj1000 Jun 27 '17 at 14:07
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    You can do a Google image search for "b2 bomb bay" (example result) and get a pretty good idea of its dimensions, and accordingly, a decent estimate of its capacity. It's also quite clear that it doesn't have external hardpoints like the B-52. Top speed (and diving depth) is much easier to keep secret - you don't peel out of a harbor at 45 knots where everyone can see you. – ceejayoz Jun 27 '17 at 15:39
  • And when those dimensions were shown publicly, they didn't put panels in place to disguise the true capability, like they do when releasing photos of cockpits or weapons stations in classified aircraft, or control rooms of classified submarines? Our government may be dumb, but our military is pretty good at keeping things secret, or even misleading a potential adversary, when it comes to the capability of a highly classified piece of equipment. – tj1000 Jun 27 '17 at 17:51
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    Look, if you want to take that approach, M-16s could have top-secret killer lasers and C-17s might have a top speed of Mach 20. Or we could just keep the conversation in the realm of what's likely. There is minimal benefit to lying about the payload capacity of the B-2 - modern wars aren't won on raw payload tonnage in this era. – ceejayoz Jun 27 '17 at 17:54
  • M16's and C17's are not guarded closely. B2's, as the nation's premier high tech bomber, is very closely guarded, as releasing its full capability can have a direct effect on the nation's strike ability. If you think an M16 is the same as a B2, and that everything that can be known is found on wikipedia, complete and totally accurate... – tj1000 Jun 28 '17 at 02:05
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    It is highly unlikely that the B-2 has a secretly larger bomb bay. Simple as that. There's no logic behind your conspiracy theory, and other posters have provided perfectly rational explanations for the difference (lack of external hardpoints being a significant one). I'm done here. – ceejayoz Jun 28 '17 at 02:09
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    @ceejayoz You seem very dismissive of the possibility that Doctor Who has provided us Time Lord technology. – yshavit Jun 28 '17 at 13:34