美国隐形轰炸机B-2

Northrop Grumman B-2 Spirit

Overview

The

Northrop

(later

Northrop

Grumman)

B-2

Spirit,

also

known

as

the

Stealth

Bomber, is an American heavy strategic bomber, featuring low observable stealth

technology designed for penetrating dense anti-aircraft defenses; it is a blended

wing body design with a crew of two. The bomber can deploy both conventional

and thermonuclear weapons, such as eighty 500 lb (230 kg)-class (Mk 82) JDAM

Global

Positioning

System-guided

bombs,

or

sixteen

2,400

lb

(1,100

kg)

B83

nuclear

bombs.

The

B-2

is

the

only

known

aircraft

that

can

carry

large

air-to-surface standoff weapons in a stealth configuration.

Development originally started under the

project

during

the

Carter

administration,

and

its

performance

was

one

of

his

reasons

for

the

cancellation

of

the

supersonic

B-1A

bomber.

ATB

continued

during the Reagan administration, but worries about delays in its introduction led

to the reinstatement of the B-1 program as well. Program costs rose throughout

development.

Designed

and

manufactured

by

Northrop

Grumman,

the

cost

of

each aircraft averaged US$$737 million (in 1997 dollars). Total procurement costs

averaged

$$929

million

per

aircraft,

which

includes

spare

parts,

equipment,

retrofitting, and software support. The total program cost including development,

engineering and testing, averaged $$2.1 billion per aircraft in 1997.

Because

of

its

considerable

capital

and

operating

costs,

the

project

was

controversial

in

the

U.S.

Congress

and

among

the

Joint

Chiefs

of

Staff.

The

winding-down

of

the

Cold

War

in

the

latter

portion

of

the

1980s

dramatically

reduced

the

need

for

the

aircraft,

which

was

designed

with

the

intention

of

penetrating

Soviet

airspace

and

attacking

high-value

targets.

During

the

late

1980s

and

1990s,

Congress

slashed

plans

to

purchase

132

bombers

to

21.

In

2008,

a

B-2

was

destroyed

in

a

crash

shortly

after

takeoff,

though

the

crew

ejected

safely.

A

total

of

20

B-2s

remain

in

service

with

the

United

States

Air

Force, which plans to operate the B-2 until 2058.

The

B-2

is

capable

of

all-altitude

attack

missions

up

to

50,000

feet

(15,000

m),

with a range of more than 6,000 nautical miles (11,000 km) on internal fuel and

over

10,000

nautical

miles

(19,000

km)

with

one

midair

refueling.

Though

originally

designed

primarily

as

a

nuclear

bomber,

it

was

first

used

in

combat

dropping

conventional

ordnance

in

the

Kosovo

War

in

1999

and

saw

further

service in Iraq and Afghanistan.

Design

The B-2 Spirit was developed to take over the USAF's vital penetration missions,

able

to

travel

deep

into

enemy

territory

to

deploy

their

ordnance,

which

could

include

nuclear

weapons.

The

B-2

is

a

flying

wing

aircraft,

meaning

it

has

no

fuselage

or

tail.

The

blending

of

low-observable

technologies

with

high

aerodynamic

efficiency

and

large

payload

gives

the B-2

significant

advantages

over previous bombers. Low observability provides a greater freedom of action

at

high

altitudes,

thus

increasing

both

range

and

field

of

view

for

onboard

sensors.

The

U.S.

Air

Force

reports

its

range

as

approximately

6,000

nautical

miles (6,900 mi; 11,000 km). At cruising altitude the B-2 refuels every six hours,

taking on up to 50 short tons (45 t) of fuel at a time.

Due

to

the

aircraft's

complex

flight

characteristics

and

design

requirements

to

maintain very-low visibility to multiple means of detection, both the development

and

construction

of

the

B-2

required

pioneering

use

of

computer- aided

design

and

manufacturing

technologies.

The

B-2

bears

a

resemblance

to

earlier

Northrop aircraft: the YB-35 and YB-49 were both flying wing bombers that had

been canceled in development in the early 1950s, allegedly for political reasons.

The resemblance goes as far as B-2 and YB-49 having the same wingspan.

As of September 2013 about 80 pilots fly the B-2. Each aircraft has a crew of two,

a pilot in the left seat and mission commander in the right, and has provisions for

a third crew member if needed. For comparison, the B-1B has a crew of four and

the

B-52

has

a

crew

of

five.

The

B-2

is

highly

automated

and,

unlike

most

two- seat

aircraft,

one

crew

member

can

sleep

in

a

camp

bed,

use

a

toilet,

or

prepare

a

hot

meal while

the

other

monitors

the

aircraft;

extensive

sleep

cycle

and

fatigue

research

was

conducted

to

improve

crew

performance

on

long

sorties.

Armaments and equipment

The

B-2, in

the

envisaged

Cold

War

scenario, was

to

perform

deep- penetrating

nuclear strike missions, making use of its stealthy capabilities to avoid detection

and

interception

throughout

missions.

There

are

two

internal

bomb

bays

in

which munitions are stored either on a rotary launcher or two bomb-racks; the

carriage

of

the weapons

loadouts

internally

results

in

less

radar

visibility

than

external mounting of munitions. The B-2 is capable of carrying 40,000 pounds of

ordnance.

Nuclear

ordnance

includes

the

B61

and

B83

nuclear

bombs;

the

AGM-129 ACM cruise missile was also intended for use on the B-2 platform.

It was decided, in light of the dissolution of the Soviet Union, to equip the B-2 for

conventional precision attacks as well as for the strategic role of nuclear-strike.

The B-2 features a sophisticated GPS- Aided Targeting System (GATS) that uses

the

aircraft's

APQ-181

synthetic

aperture

radar

to

map

out

targets

prior

to

deployment

of

GPS-aided

bombs

(GAMs),

later

superseded

by

the

Joint

Direct

Attack

Munition

(JDAM).

In

the

B-2's

original

configuration,

up

to

16

GAMs

or

JDAMs

could

be

deployed;

an

upgrade

program

in

2004

raised

the

maximum

carriable capacity to 80 JDAMs.

The B-2 has various conventional weapons in its arsenal, able to equip Mark 82

and Mark 84 bombs, CBU-87 Combined Effects Munitions, GATOR mines, and the

CBU-97 Sensor Fuzed Weapon. In July 2009, Northrop Grumman reported the B-2

was compatible with the equipment necessary to deploy the 30,000 lb (14,000 kg)

Massive

Ordnance

Penetrator

(MOP),

which

is

intended

to

attack

reinforced

bunkers; up to two MOPs could be equipped in the B-2's bomb bays, the B-2 is

the only platform compatible with the MOP as of 2012. As of 2011, the AGM-158

JASSM cruise missile is an upcoming standoff munition to be deployed on the

B-2

and

other

platforms.

This

is

to

be

followed

by

the

Long

Range

Standoff

Weapon which may give the B-2 a standoff nuclear capability for the first time.

Avionics and systems

In order to make the B-2 more effective than previous bombers, many advanced

and modern avionics systems were integrated into its design, these have been

modified and improved following a switch to conventional warfare missions. One

system is the low probability of intercept AN/APQ-181 multi-mode radar, a fully

digital

navigation

system

that

is

integrated

with

terrain-following

radar

and

Global

Positioning

System

(GPS)

guidance,

NAS-26

astro-inertial

navigation

system

(first

such

system

tested

on

the

Northrop

SM-62

Snark

cruise

missile)

and a Defensive Management System (DMS) to inform the flight crew of possible

threats.

The

onboard

DMS

is

capable

of

automatically

assessing

the

detection

capabilities of identified threats and indicated targets.

For safety and fault-detection purposes, an on-board test system is interlinked

with the majority of avionics on the B-2 to continuously monitor the performance

and

status

of

thousands

of

components

and

consumables;

it

also

provides

post-mission servicing instructions for ground crews. In 2008, many of the 136

standalone distributed computers on board the B-2, including the primary flight

management computer, were being replaced by a single integrated system. The

avionics

are

controlled

by

13

EMP-resistant

MIL-STD-1750A

computers,

which

are

interconnected

through

26

MIL- STD-1553B-busses;

other

system

elements

are connected via optical fiber.

In

addition

to

periodic

software

upgrades

and

the

introduction

of

new

radar-absorbent

materials

across

the

fleet,

the

B-2

has

had

several

major

upgrades

to

its

avionics

and

combat

systems.

For

battlefield

communications,

both Link-16 and a high frequency satellite link have been installed, compatibility

with

various

new munitions

has

been

undertaken,

and

the

AN/APQ-181

radar's

operational

frequency

was

shifted

in

order

to

avoid

interference

with

other

operator's

equipment.

The

arrays

of

the

upgraded

radar

features

were

entirely

replaced

to

make

the

AN/APQ-181

into

an

active

electronically

scanned

array

(AESA) radar.

To

keep

the

B-2

relevant

against

increasingly

sophisticated

air

defenses

with

greater

computer

processing

power

that

may

be

able

to

detect

the

aircraft

through its stealth measures, the Air Force is working to upgrade the Defensive

Management

System

(DMS),

which

uses

sensors,

passive

receivers,

and

computers

to

alert

crew

about

the

location

of

enemy

air

defense

systems.

Though it will not counter air threats, it will be more capable of identifying and

locating them before the aircraft enters strike range. The upgraded DMS will help

detect radar emissions from air defenses to allow changes to the auto-router's

mission planning information while in- flight so it can receive new data quickly to

plan a route that minimizes exposure to dangers. The DMS upgrade is slated to

enter service by 2021.

Flight controls