Post on 16-Dec-2015
The Nature of the Blast
Efficiency of explosion Kind and shape of blasts Blast effects, range & damage Thermal effects Radiation effects
The results of the weapons test programs
Blast—40-60% of total energy Thermal radiation—30-50% of total energy Ionizing radiation—5% of total energy Residual radiation (fallout)—5-10% of total energy
Classifications of blasts Surface Blast:
fireball in touch with surfacevaporization of surface structures through blastand firestorm, immediate radioactive fallout
High Altitude Air Blast: fireball > 100,000 ft (>3000m)interrupts satellite based communicationthrough electromagnetic pulse (EMP)
Low Altitude Air Blast:fireball < 100,000 ft (without touching ground)generates shock waves, pressure differenceartificial for large areal damage, sea battle
Subsurface Blast:Underwater burstgenerates surge
Surface Blast – the fireball
Central temperature: ~10,000,000 KImmediate vaporization of material!Central pressure: ~33000 atm
Radiation release & absorption in surrounding matter generates red-glow intense luminosity. Expansion of fireball through internal pressure Fireball rises like hot air balloon
StokesAugust 1957
1500 Foot Balloon19 kt
Fireball expansion
psiatmT
T
p
p
KTatmpKT
constVTVp
000,503300300
000,000,1
101,1,300
;
1
2
1
2
6211
Pressure evolution within the fireball:
tem
pera
tur
e
pressure
Sedov Taylor approximation (valid of first 0.1s) allowed Russians to estimate the power of the Trinity bomb from the expansion time conditions
TNTktE
JTNTkt
mstJtP
PKE
P
P
mtr
mkgKtrKE
10
1018.41
)1(1004.41074.7
][950
/1,1
12
135/814
00
00
5/2
30
5/25
t r
0.1 ms 24 m0.4 ms 42 m0.7 ms 52 m0.9 ms 60 m
Expansion speed
sftskmv
skmTRcc
v ss
/000,240/8015.1
202
5.1;/201
2
Initial expansion speed v (T≈1,000,000 K)
cs is the speed of sound in the vaporized gas is the specific heat ratio of the gasR is the gas constant: 287 [J/kg K]; T is temperature [K]
Cool-down to T≈3,000 after 15 ms due to radiation losses
sftskmv
skmTRcc
v ss
/500,24/8125.1
12
25.1;/11
2
Ideal gas
Fully ionized plasma
The shock front developmentAfter ~10 second the fireball expands with constant rate of ~300 ft/s
After ~ 1minute fireball has cooled and radiation emission ceases!
Analysis of Fire ball
Sedov-Taylor Blast analysis
5/2
5/1
0
tK
ER
Valid as long as shock is super sonic: K≈1Approximation allowed Russian scientists to estimate the power of US Trinity bomb.
General Features – the mushroom the emergence of the mushroom shape
Absorption of cool airtriggers fast toroidal circulation of hot gases and causes upwardmotion forming the stem and mushroom.
Condensation of water changes red brownish color ofcloud towards white!
Strong upward windDrags dirt and debrisInto the cloud mixingwith radioactive material
Cloud rises in heightwith ~ 440 ft/s
Cloud AltitudeMaximum altitude for cloudrise is reached after ~ 4min. RATE OF RISE OF THERADIOACTIVE CLOUD FROM a I-MEGATON AIRBURSTHeight Time Rate of Rise(miles) (min) (mph) 2.0 0.3 330 3.0 40.7 270 4.0 61.1 220 5.0 102.5 140 6.0 123.8 27
Cloud height & cloud radiusdepend on the magnitude ofthe explosion, increase ofboth radius & height scaleswith explosion yield.
Chimney effect again!
v=wind velocity in m/sg=9.8 m/s2 earth accelerationH=height of heat column in [m]To=outside temperature, KTi=inside temperature in K
i
oi
T
TTHgv 265.0
For typical firestorm:H ≈ 10,000 mTi ≈ 1,000,000 KTo ≈ 300 K
➱ v ≈ 288m/s = 647 miles/hHurricane speeds ~100 miles/hConventional firestorm ~220 miles/h