Papers and exams. Delivery systems. Centrifuge enrichment. Proliferation

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1 Papers and exams 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).

2 Last assignments Writing assignment due March 11: a briefing paper to the President 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 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 to me your exam answers; otherwise, similar style to midterm exam. If you do not have a laptop or tablet, me.

3 Final paper due March 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

4 Gun-type 235 U bomb Relatively easy to make a bomb; industrial-scale effort required to enhance the isotopic concentration of 235 U from 0.7% to > 40%.

5 Implosion-type 239 Pu bomb Easier to get 239 Pu (neutrons in a reactor on the common isotope 238 U, followed by chemical separation. Harder to produce implosion using conventional explosives.

6 Little Boy and Fat Man Hiroshima: Little Boy, 15 kt. Nagasaki: Fan Man, 21 kt. USSR: copy of Fat Man tested on Aug. 29, 1949 before indigenous designs allowed.

7 Modern example: W80 B61: developed by Los Alamos (airplane-dropped bomb; up to 340 kt). Smaller version sought for cruise missles; W80 developed by Los Alamos pounds, dial-a-yield from kt, 31 long, 12 diameter.

8 The Cold War At their peak around 1985, the US and USSR each had about 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.

9 Nuclear weapons tests From Wikipedia:

10 Nevada test site Test Buster-Jangle Dog, Nevada Test Site, Craters at the Nevada Test Site.

11 Perfecting nuclear weapons The WWII bombs were very conservative in design. 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. 235 U or 239 Pu triggers with 238 U 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?

12 MIRV bus: multiple independent re-entry vehicle (on a missle). CEP (circular error probable) is 30 m for Tomahawk (cruise missile), m for LG-118A (land-based missile; 8 warheads; decommissioned 2005!), m for Trident II (submarine-based missile; up to 8 warheads each; in the past had 2700 warheads on 14 submarines). MIRVs US W-88 warhead: 470 kt m long, 0.55 m max diameter, 360 kg mass.

13 Delivering nuclear weapons Both the USA and the USSR have had a triad of delivery systems: 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 meters. One missile can carry multiple warheads. Submarine-based or Sea-Launched Ballistic Missiles (SLBMs): 20 minute flight time, circular error probable (CEP) of m. Deep, quiet boomer or ballistic missile submarines with nuclear power plants are very difficult to detect.

14 B-52 with AGM-86B 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.

15 Minuteman III ICBM Minuteman III silo Present sites (450 single-warhead missiles on active duty)

16 Ohio class submarines 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.

17 Trident II missile 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.

18 Nuclear war strategies Ballistic missile warheads arrive at 15, 000 mph and are maneuverable; missile defense is not easy! 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 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).

19 Gas centrifuges The modern approach to uranium : put UF 6 in centrifuges at krpm to get gravitational force of about 10 6 g. Use stages to get good enhancement of 235 U relative to 238 U.

20 Gernot Zippe Austrian physicist working for Luftwaffe during WW II. Captured by USSR at end of WW II, and ended up leading their centrifuge program. Released by USSR in Found western centrifuge programs to be way behind. University of Virginia, late 1950s: recreated USSR design. Left US after demand that he become a citizen to continue this work. Returned to Europe, and was a founder of the UK/Dutch/German centrifuge company URENCO. Gernot Zippe ( ), from

21 s in Iran technology likely spread from France to Pakistan, and from there to Iran. Countries that sign the nuclear Non- 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 for nuclear power. Reactors only require from 0.7% to %. IAEA found Iran to be in non-compliance with nuclear materials reporting obligations in The pictures that follow: from the New York Times on April 29, 2008; and March 14, 2009.

22 Natanz, Iran

23 Photos from Iran A B C M D I E F G H J K L N O P A: Intelligence Minister. B. President. C: Defense Minister. D: Head of Atomic Energy

24 schematic

25 The nuclear club 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).

26 Nuclear inbreeding? Graphic from Dec. 8, 2008 New York Times based on Reed & Stillman:

27 Getting good at it Modern US arsenal: 500! (Figure: Reed & Stillman)

28 Fission to fusion (Reed & Stillman)

29 India First test: 1974, with yield about 10 kt tests: (Reed & Stillman)

30 (Reed & Stillman) Pakistan Help from China around Pakistani test in China on May 26, 1990? (Reed and Stillman). Pakistan s 1998 tests:

31 Abdul Qadeer (AQ) Khan PhD in metallurgical engineering in Belgium, Worked at URENCO (founded by Zippe) Head of Pakistani uranium 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.

32 North Korea A.Q. Khan s CHIC-4/A 235 U design, based on information from China to Pakistan circa 1982? Attempts at trickier 239 Pu implosion weapons, since they are doing reactor fuel reprocessing? Oct. 9, 2006: first underground nuclear test. Yield about 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...

33 Are they gone? No! Still number in the thousands. USA produced 994 metric tonnes of highly enriched uranium, and 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).

34 Pantex USA has 14,000 plutonium pits stored at Pantex plant near Amarillo, Texas.

35 The responsibility of physicists 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

36 History of major war deaths Year (CE) War Three Kingdoms War, China An Lushan Rebellion, China Crusades Mongol conquests Late Yuan warfare Conquest of Timur French wars of religion Qing dynasty conquest Thirty Year's War, Holy Roman Empire Polish-Lithuanian war Napoleonic wars Shaka's conquests, Africa Taiping Rebellion, China Dungan revolt, China Paraguayan War Mexican Revolution World War I Russian Civil War World War II Korean War Vietnam War Soviet war in Afghanistan Iran-Iraq war Second Sudanese civil war % world population killed 2.01% 14.60% 0.83% 11.32% 6.70% 3.91% 0.57% 4.80% Second Congo War 1.02% 0.65% 0.53% 0.20% 1.83% 0.73% 0.04% 0.05% 1.70% 0.37% 2.30% 0.10% 0.12% 0.83% 0.02% 0.02% 0.07% 1

37 History of major war deaths 16.00% 14.00% 12.00% % world population killed 10.00% 8.00% 6.00% 4.00% 2.00% 0.00% Year (CE) 2

38 Earth s atmosphere, and beyond 10 0 Atmospheres Mt. Whitney Mt. Everest Airliner U Shuttle (low orbit) ISS Altitude (km)

39 Basics of orbits A stable circular orbit arises when centripetal force provided by gravity: Gravity: F g = GmM/r 2 where G = m 3 kg 1 s 2, and M = kg for earth. Centripetal: F c = mv 2 /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. Solve for r: G mm r 2 = m (2πr) 2 r T 2 T 2 = (2π)2 r 3 MG ( MGT 2 r = (2π) 2 ) 1/3 with T = 1 day, gives 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.

40 Energy of orbits Expression for gravitational potential energy is U = GmM/r, so [ 1 U = GmM 1 ] r 2 r 1 1 kg from earth s surface to 200 km above earth: r 1 = 6378 km, r 2 = 6578 km, so U = J. 1 kg to an infinite distance away from earth: r 1 = 6378 km, 1/r 2 = 0, so U = J. Kinetic energy of an object in circular motion: v = (2πr)/T so KE = 1 2 m(2πr)2 T 2 Object on earth s surface with r = 6378 km and T = 24 hours: KE= J. Object at 200 km orbit with r = 6578 km and T = 5412 seconds: KE= J.

41 Energy of orbits II Let s look at all of these energies for 1 kg mass in units of MJ (10 6 J): Kinetic energy KE Gravitational energy U Earth s surface km orbit Outer space 62.4 So getting to 200 km orbit requires about half the energy of escaping earth altogether.

42 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

43 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 and the countenancing of the Smithsonian Institution, 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) Robert Goddard,