Delivery systems Papers and exams
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Orbits • I’ve graded everything but the water tower assignment (will return that on Thursday). • I spent a lot of time making comments on your papers. I really found them to be quite good! The large number of comments are not to express unhappiness, but to give you constructive criticism for future improvements. • What about grades? I tend to not give many perfect scores, but to go along with that I tend to regard the A/B threshold as being in the low 80% range on my grading scale (and the B/C threshold as in the low 70% range). Delivery systems Last assignments
Centrifuge enrichment Iran’s centrifuges Proliferation • Writing assignment due March 11: a briefing paper to the President Orbits of the USA on a topic where some physics knowledge is required (see next slide). • It is better to pick a specific subtopic with specific proposed actions. This is not a philosophy class but Physics for Future Presidents, so emphasize information relevant to the problem and solution. It’s good to show passion for a solution, but passion without solid information is not well matched to this class. • You are encouraged to email me about your proposed topic; I can give you a few suggestions and ideas. • Exam on Tuesday, March 19 at 7 pm. Exam will be open laptop or tablet, where you email to me your exam answers; otherwise, similar style to midterm exam. If you do not have a laptop or tablet, email me. Delivery systems Final paper due March 11
Centrifuge enrichment Iran’s centrifuges
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Orbits 8–12 page briefing paper, double-spaced, with citations. Submit through SafeAssign. I’ll set the SafeAssign deadline to be March 13 at 11 pm... • Abstract (roughly half a page, summarizing your paper; use italic font) • Statement of problem • Relevant information (the quality of the sources you use will be part of your grade) • Proposed action, including discussion of costs and benefits • Arguments against your proposed action, and your counter-arguments • Conclusion 235 Delivery systems Gun-type U bomb
Centrifuge enrichment Relatively easy to make a bomb; industrial-scale effort required to Iran’s centrifuges enhance the isotopic concentration of 235U from 0.7% to > 40%. Proliferation ∼
Orbits 239 Delivery systems Implosion-type Pu bomb
Centrifuge 239 238 enrichment Easier to get Pu (neutrons in a reactor on the common isotope U, Iran’s centrifuges followed by chemical separation. Harder to produce implosion using Proliferation conventional explosives. Orbits Delivery systems Little Boy and Fat Man
Centrifuge Hiroshima: Little Boy, 15 kt. Nagasaki: Fan Man, 21 kt. enrichment Iran’s centrifuges
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USSR: copy of Fat Man tested on Aug. 29, 1949 before indigenous designs allowed. Delivery systems Modern example: W80
Centrifuge enrichment • B61: developed by Los Alamos 1961–1968 (airplane-dropped Iran’s centrifuges bomb; up to 340 kt). Proliferation Orbits • Smaller version sought for cruise missles; W80 developed by Los Alamos 1976–1982. • 290 pounds, dial-a-yield from 5–150 kt, 31” long, 12” diameter. Delivery systems The Cold War
Centrifuge enrichment Iran’s centrifuges
Proliferation • At their peak around 1985, the US and USSR each had about Orbits 20,000–30,000 nuclear weapons. • Nuclear testing: a total of about 2000 tests worldwide, including about 500 above-ground. • Both the US and the USSR developed a triad of weapons delivery systems: bombers, intercontinental ballistic missiles (∼30 minutes “door-to-door delivery”), and missile-launching submarines. Other nations have one or two parts of such a triad. • Strategic weapons: destroy big targets in the interior of the opposing country (missile launch sites, command and control centers, and cities as a last resort). First strike; “use them or lose them.” • Tactical weapons: destroy troop concentrations, command centers, etc. on the battlefield. Delivery systems Nuclear weapons tests
Centrifuge enrichment From Wikipedia: Iran’s centrifuges
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Orbits Delivery systems Nevada test site
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Test “Buster-Jangle Dog,” Nevada Test Site, 1951.
Craters at the Nevada Test Site. Delivery systems Perfecting nuclear weapons
Centrifuge enrichment Iran’s centrifuges Proliferation • The WWII bombs were very conservative in design. Orbits • Weapons testing allowed various tricks to be perfected. • Improved conventional high exposives that won’t go off in accidents (e.g., aircraft crash and fire). • Levitated implosion cores (to drive a nail, do you push with a hammer, or swing it?) • Small accelerators as neutron initiators. • 235U or 239Pu triggers with 238U fission boosts. • Improved radiation heating of Li-based fusion cores. • Permissive Action Links (PALs) of increasing sophistication, so that only a specific, secret electrical signal sequence will arm a bomb. • A danger: are US weapons too “tweaky” to be robust to ageing? Will they rust in peace? Codeword: stockpile stewardship. New generation of robust, simpler weapons? Delivery systems MIRVs
Centrifuge enrichment MIRV bus: multiple independent re-entry ve- Iran’s centrifuges hicle (on a missle). CEP (circular error prob- Proliferation able) is 30 m for Tomahawk (cruise missile), Orbits 80–100 m for LG-118A (land-based missile; 8 warheads; decommissioned 2005!), 90–120 m for Trident II (submarine-based missile; up to 8 warheads each; in the past had 2700 warheads on 14 submarines).
US W-88 warhead: 470 kT. 1.75 m long, 0.55 m max diameter, ∼ 360 kg mass. Delivery systems Delivering nuclear weapons
Centrifuge enrichment Iran’s centrifuges Both the USA and the USSR have had a triad of delivery systems: Proliferation • Orbits Airplane delivery (originally “dumb” air-dropped bombs; now “smart” or guided bombs using laser targeting, or GPS). Slow, but can be recalled. • Modern variant: bombers carrying Air-Launched Cruise Missiles (ALCMs) with ∼ 30 m circular error probable (CEP) or targeting accuracy. • Land-based InterContinental Ballistic Missiles (ICBMs): ∼ 30 minute flight time, circular error probable (CEP) or targeting accuracy of 80–100 meters. One missile can carry multiple warheads. • Submarine-based or Sea-Launched Ballistic Missiles (SLBMs): ∼ 20 minute flight time, circular error probable (CEP) of 90–120 m. Deep, quiet “boomer” or ballistic missile submarines with nuclear power plants are very difficult to detect. Delivery systems B-52 with AGM-86B
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B-52 carrying AGM-86B cruise missiles (one B-52 can carry 20). The AGM-86B is 20 feet long, weighs 3200 pounds, and has a range of over 1500 miles. We have about 85 B-52s in service. Delivery systems Minuteman III ICBM
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Present sites (450 single-warhead missiles on active duty) Minuteman III silo Delivery systems Ohio class submarines
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Ohio-class submarine: artist rendering of missile launch. One sub can carry up to 24 Trident II missiles; or 154 Tomohawk sea-launched cruise missiles, including those with W80 (150 kt) warheads. We have 14 Ohio-class subs in service. Delivery systems Trident II missile
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Orbits Trident II missile launched from a submarine. With a load of four W88 (475 kt) or eight W76 (100 kt) warheads, the missile has a range of around 7000 miles. Delivery systems Nuclear war strategies
Centrifuge enrichment • Ballistic missile warheads arrive at ∼ 15, 000 mph and are Iran’s centrifuges maneuverable; missile defense is not easy! Proliferation • Orbits Mutual Assured Destruction (MAD): if you hit me, I’m sure to hit you. • Destroying a city (mutually assured destruction, or MAD): a few 1,000 kt TNT equivalent (i.e., megaton yield) at 1–2 mile accuracy is sufficient to kill a large fraction of the population in even the largest cities. China reached this capability ca. 1975 even as a poor, agrarian society. • Does MAD hold any meaning with enemies who practice suicide bombings? • MAD requires knowing the return address... • First strike: I try to knock out all of your missiles, so you can’t hit me. • No need to target cities. • “Winnable” or limited nuclear war? “Use ‘em or lose ‘em”–but you can’t be sure of knocking out 100%. • Was actively discussed by the “nuclear priesthood” during Reagan’s presidency (USA)/Brezhnev’s premiership (USSR). Delivery systems Gas centrifuges
Centrifuge enrichment Iran’s centrifuges The modern approach to uranium enrichment: put UF6 in centrifuges at 6 Proliferation 50–70 krpm to get gravitational force of about 10 g. Use 10–20 stages 235 238 Orbits to get good enhancement of U relative to U. Delivery systems Gernot Zippe
Centrifuge enrichment • Austrian physicist working for Iran’s centrifuges
Proliferation Luftwaffe during WW II. Orbits • Captured by USSR at end of WW II, and ended up leading their centrifuge program. • Released by USSR in 1956. Found western centrifuge programs to be way behind. • University of Virginia, late 1950s: recreated USSR design. Left US after Gernot Zippe demand that he become a citizen to (1917–2008), from continue this work. www.uranuss.at • Returned to Europe, and was a founder of the UK/Dutch/German centrifuge enrichment company URENCO. Delivery systems Centrifuges in Iran
Centrifuge enrichment Iran’s centrifuges
Proliferation Orbits • Centrifuge technology likely spread from France to Pakistan, and from there to Iran. • Countries that sign the nuclear Non-Proliferation Treaty (NPT; 1968) gain the right to develop peaceful uses of nuclear power, with monitoring from the International Atomic Energy Agency (IAEA). • Iran is part of NPT and says it is only developing uranium enrichment for nuclear power. Reactors only require enrichment from 0.7% to 2.5–3.5%. IAEA found Iran to be in non-compliance with nuclear materials reporting obligations in 2005. • The pictures that follow: from the New York Times on April 29, 2008; and March 14, 2009. Delivery systems Natanz, Iran
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Orbits Delivery systems Photos from Iran
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Proliferation A B C Orbits
D M
I E F P G J L O H K N
A: Intelligence Minister. B. President. C: Defense Minister. D: Head of Atomic Energy Delivery systems Centrifuge schematic
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Orbits Delivery systems The nuclear club
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• Declared nuclear weapons states with fission/fusion: USA (1945), USSR/Russia (1949), United Kingdom (1952), France (1960), People’s Republic of China (1964). • Additional declared states: India (1974), Pakistan (1998), North Korea (2006). • Undeclared states: Israel (1967? 1979?), South Africa (1979?; dismantled six nukes and renounced program in 1990). Delivery systems Nuclear inbreeding?
Centrifuge enrichment Iran’s centrifuges
Proliferation Orbits Graphic from Dec. 8, 2008 New York Times based on Reed & Stillman: Delivery systems Getting good at it
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Modern US arsenal: ∼ 500! (Figure: Reed & Stillman) Delivery systems Fission to fusion
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(Reed & Stillman) Delivery systems India
Centrifuge enrichment Iran’s centrifuges First test: 1974, with yield about 10 kt. 1998 tests: Proliferation
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(Reed & Stillman) Delivery systems Pakistan
Centrifuge Help from China around 1982. Pakistani test in China on May 26, 1990? enrichment Iran’s centrifuges (Reed and Stillman).
Proliferation Pakistan’s 1998 tests:
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(Reed & Stillman) Delivery systems Abdul Qadeer (AQ) Khan Centrifuge • PhD in metallurgical engineering in enrichment Iran’s centrifuges Belgium, 1972. Proliferation • Worked at URENCO (founded by Orbits Zippe) 1972–1975. • Head of Pakistani uranium enrichment program in 1976; rivalry and independence from Pakistani Atomic Energy Commission. • 2004: televised confession to selling nuclear weapons technology to Iran, North Korea, and Libya. Plans and kits turned over by Libya to International Atomic Energy Agency. Khan under house arrest. • 2008: in poor health; released from house arrest but not allowed to travel. Publicly disavows 2004 confession. Died in 2009. Delivery systems North Korea
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Orbits • A.Q. Khan’s CHIC-4/A 235U design, based on information from China to Pakistan circa 1982? Attempts at trickier 239Pu implosion weapons, since they are doing reactor fuel reprocessing? • Oct. 9, 2006: first underground nuclear test. Yield about 0.5–1 kt? • May 25, 2009: second test. Yield around 4 kt? • Feb. 11, 2013: third test. Yield around 6 kt? 15 kt? Claim of a more compact weapon. • As with missiles, they are far from perfecting nuclear weapons. However, getting hit by 4 kt still leads to a pretty bad day... Delivery systems Are they gone?
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• No! Still number in the thousands. • USA produced 994 metric tonnes of highly enriched uranium, and 111.4 metric tonnes of plutonium. • USSR produced 1200 metric tonnes of highly enriched uranium, and 150 metric tonnes of plutonium. • 0.1% of USSR production is enough for 16 uranium bonbs and 25 plutonium bombs (Reed & Stillman). Delivery systems Pantex
Centrifuge enrichment Iran’s centrifuges
Proliferation Orbits USA has ∼ 14,000 plutonium pits stored at Pantex plant near Amarillo, Texas. Delivery systems The responsibility of physicists
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J. Robert Oppenheimer, director of the Manhattan Project: In some sort of crude sense which no vulgarity, no humor, no overstatement can quite extinguish, the physicists have known sin; and this is a knowledge which they cannot lose. From http://en.wikiquote.org/wiki/Robert_Oppenheimer % world population History of Year (CE) War killed major war 195 Three Kingdoms War, China 2.01% 759 An Lushan Rebellion, China 14.60% deaths 1193 Crusades 0.83% 1340 Mongol conquests 11.32% 1354 Late Yuan warfare 6.70% 1387 Conquest of Timur 3.91% 1580 French wars of religion 0.57% 1639 Qing dynasty conquest 4.80% Thirty Year's War, Holy Roman 1633 Empire 1.02% 1658 Polish-Lithuanian war 0.65% 1810 Napoleonic wars 0.53% 1822 Shaka's conquests, Africa 0.20% 1858 Taiping Rebellion, China 1.83% 1870 Dungan revolt, China 0.73% 1867 Paraguayan War 0.04% 1916 Mexican Revolution 0.05% 1916 World War I 1.70% 1919 Russian Civil War 0.37% 1942 World War II 2.30% 1952 Korean War 0.10% 1965 Vietnam War 0.12% 1984 Soviet war in Afghanistan 0.83% 1984 Iran-Iraq war 0.02% 1994 Second Sudanese civil war 0.02% 2001 Second Congo War 0.07% http://en.wikipedia.org/wiki/List_of_wars_and_anthropogenic_disasters_by_death_toll 1 History of major war deaths
16.00%
14.00%
12.00%
10.00%
8.00%
6.00%
4.00% % world population killed
2.00%
0.00% 0 500 1000 1500 2000 Year (CE) 2 Earth’s atmosphere, and beyond 100
10-1
-2 Airliner 10 U-2 Mt. Whitney Mt. Everest 10-3
10-4 Atmospheres 10-5 Shuttle ISS (low orbit) 10-6
10-7 3 4 6 8 10 20 40 60 100 200 400 Altitude (km) 3 Delivery systems Basics of orbits Centrifuge A stable circular orbit arises when centripetal force provided by gravity: enrichment 2 −11 3 −1 −2 Iran’s centrifuges • Gravity: Fg = GmM/r where G = 6.67 × 10 m kg s , and Proliferation M = 5.97 × 1024 kg for earth. Orbits 2 • Centripetal: Fc = mv /r where v = (2πr)/T with r being the radius from the center of the earth and T being the orbital period (time). • Set them equal; m drops out.
mM m (2πr)2 (2π)2r3 G = ⇒ T2 = r2 r T2 MG • Solve for r: MGT2 1/3 r = (2π)2 with T = 1 day, gives 4.2 × 107 m or 26,000 miles (earth’s radius is 6378 km or 4000 miles). Geostationary orbit. • For r = 6578 km (200 km above earth’s surface), T = 5312 seconds or 88.5 minutes. Delivery systems Energy of orbits
Centrifuge enrichment • Expression for gravitational potential energy is U = −GmM/r, so Iran’s centrifuges Proliferation 1 1 Orbits ∆U = GmM − r2 r1
• 1 kg from earth’s surface to 200 km above earth: r1 = 6378 km, 6 r2 = 6578 km, so ∆U = 1.898 × 10 J. • 1 kg to an infinite distance away from earth: r1 = 6378 km, 7 1/r2 = 0, so ∆U = 6.243 × 10 J. • Kinetic energy of an object in circular motion: v = (2πr)/T so
1 (2πr)2 KE = m 2 T2
• Object on earth’s surface with r = 6378 km and T = 24 hours: KE= 1.07 × 105 J. • Object at 200 km orbit with r = 6578 km and T = 5412 seconds: KE= 3.027 × 107 J. Delivery systems Energy of orbits II
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Orbits Let’s look at all of these energies for 1 kg mass in units of MJ (106 J): Kinetic energy KE Gravitational energy U Earth’s surface 0.1 200 km orbit 30.3 1.9 Outer space 62.4 So getting to 200 km orbit requires about half the energy of escaping earth altogether. Gravitational potential energy
• Recall that putting 1 kg into a 200 km orbit around earth requires 32.1 MJ • Raise 1 kg from moon’s surface radius r=1,700 (M=7.3x1022 kg) to r⇒∞: ΔU=2.9 MJ. • Raise 1 kg from Mars’ surface radius r=3,400 (M=6.4x1023 kg) to r⇒∞: ΔU=13 MJ. • If we could do this with 100% efficiency, it would be cheap! $1 of oil buys you 57 MJ of chemical energy. • Short of building space elevators, however, we’re stuck with rockets... • Shuttle launch: $500M for 25,000 kg, or $20,000/kg to low earth orbit
goal is $1,000/kg to earth orbit
4 Rockets A Method for Reaching Extreme Altitudes, by Robert Goddard (1919)
[A]fter the rocket quits our air and really starts on its longer journey, its flight would be neither accelerated nor maintained by the explosion of the charges it then might have left. To claim that it would be is to deny a fundamental law of dynamics, and only Dr. Einstein and his chosen dozen, so few and fit, are licensed to do that... That Professor Goddard, with his 'chair' in Clark College Robert Goddard, and the countenancing of the Smithsonian Institution, 1882-1945 does not know the relation of action to reaction, and of the need to have something better than a vacuum against which to react -- to say that would be absurd. Of course he only seems to lack the knowledge ladled out daily in high schools. New York Times, Jan. 13, 1920 (retraction issued on July 17, 1969) 5