US National Research Council report : Defending Planet Earth: Near-Earth Object Surveys and Hazard Mitigation Strategies Final Report
"Nuclear explosives constitute a mature technology, with well-characterized outputs. They represent by far the most mass efficient method of energy transport and should be considered as an option for NEO mitigation. Nuclear explosives provide the only option for large NEOs (> 500 meters) when the time to impact is short (years to months), or when other methods have failed and time is running out. The extensive test history of nuclear explosives demonstrates a proven ability to provide a tailored output (the desired mixture of x rays, neutrons, or gamma rays) and dependable yields from about 100 tons to many megatons of TNT-equivalent energy. Coupled with this test history is an abundance of data on the effects of the surface and subsurface blasts, including shock generation and cratering.
Various methods have been proposed for using nuclear explosions to reduce or eliminate an NEO threat; for a given mass of the NEO the warning time is a primary criterion for choosing among them.
With decades of warning, the required change in velocity (ΔV) from the explosion is millimeters to a centimeter per second and can be met for NEOs many kilometers in diameter. This range of values is much less than the 25 to 50 cm/s escape velocity from moderate to large (500 to 1000 meter) bodies, so it is reasonable to assume that such a small ΔV would not lead to the target’s fragmentation or to excessive ejecta (i.e., debris thrown off the object). This expectation is met in hydrodynamic simulations presented here that show that nuclear explosions can provide ΔV from 0.7 to 2.4 cm/s, for payload masses less than a ton (including the nuclear device’s fuse and environmental cocoon). In models of NEOs with surface densities as in terrestrial environments, nearly 98 percent of a body remains bound as a single object through only its own weak gravity. The small amount of ejecta expands over the decades to form a large cloud of low-density debris, reducing its posed threat by another factor of 104 to 105. The amount of the ejecta depends on the surface porosity. As in the case of kinetic impacts, a dissipative, low-density surface will reduce the amount of ejecta, thus reducing the ΔV."
By TIM PADGETT / ON THE U.S.S. CARL VINSON Tim Padgett / On The U.s.s. Carl Vinson –
Tue Jan 19, 3:30 am ET
The grisly injuries, food scarcity and lack of shelter are agony enough for Haitians in the wake of last week's devastating earthquake. But even those travails may not be as dire as the potentially deadly dehydration that millions of quake victims are suffering, especially in the capital, Port-au-Prince. With the city's waterworks incapacitated, and the relief supply effort only now getting sufficiently energized, ramping up water delivery could mean the difference between alleviating the misery and exacerbating it.
The answer may lie in the Caribbean water that the two million residents of Port-au-Prince see every day but can't drink. Sitting off the coast of Haiti, the aircraft carrier U.S.S. Carl Vinson can make some 400,000 gallons of its own fresh water every day, and much of it will soon be going ashore. The nuclear-powered vessel, which had been heading to its new home port in San Diego when it was diverted to Haiti hours after the quake, has massive desalination capacity - purifying the same ocean saltwater it traverses - and the Vinson has a daily excess of 200,000 gallons "that we can give away," says Cmdr. William McKinley, who oversees the desalination process.
The US manned space program is the ultimate symbol of American progress and technological prominence.Unfortunately, the US is rapidly approaching a situation where Americans may have no domestic manned access to space for nearly decade! Meanwhile, China is expected to launch the first components of their military space station into orbit before the end of the year.
A year from now, many Americans who usually don't pay much attention to the manned space program are probably going to be shocked to discover that while Russia and China are launching their cosmonauts and taikonauts into space, the US will have to spend tax payer dollars to pay the Russians in order for our astronauts to reach the predominantly US funded International Space Station.
And this will probably also surprise a lot of people out side of the US. America is already perceived by growing numbers around the world as a declining political and economic power. This perception will only be enhanced if the US has no domestic manned space flight capability for several years which will further reduce America's prestige and influence around the world.
How the US reached this situation is both technological and political. In 1991, President George H. W. Bush authorized a National Launch Systems (NLS) study to outline alternatives to the shuttle. One of the interesting options was a NLS 2 configuration which converted the space shuttle external tank into a rocket booster capable of launching 23 metric tonne manned and unmanned payloads to LEO. A second concept, NLS 1, added the space shuttles two 4-segment rocket boosters which would enable it to carry about 68 metric tonnes into orbit. Today, the NLS 1 concept is currently known as the DIRECT concept and is one of the directly shuttle derived HLV concepts advocated by the Augustine commission. Unfortunately, President Bush senior's National Launch System was never acted upon.
In 1996, the highly complex SSTO X-33 Venture Star was proposed as a replacement for the current space shuttle program by the Clinton administration over an equally innovative but much less complex SSTO Delta Clipper design. The Venture Star was also to operate through commercial means with NASA only purchasing launches through a commercial provider. Unfortunately, due the complexities of the design, construction of a Venture Star prototype was halted by the Clinton Administration in 1999 and finally canceled by the Bush administration in 2001. It was not until after 2004, when President George W. Bush announced his Vision for Space Exploration, that the Ares 1, was eventually proposed as another space shuttle successor. However, the Ares 1 was to be part of a larger program to return America to the Moon and would also require the development of a new heavy lift vehicle and lunar landing vehicle. This program was eventually named the Constellation program.
Now, six years later, when the current space shuttle fleet is scheduled to be decommissioned after 2010, there is some question as to the viability and expense of developing the Ares 1. Additionally, practically all of NASA's Constellation development money has gone into funding the Ares I and the the Orion-CEV while virtually no funds have been utilized for the development of the Constellation program's heavy lift vehicle, EDS (Earth Departure Stage), or Altair lunar lander.
One Augustine commission has suggestion is that NASA should utilize its funds to focus on developing a heavy lift vehicle instead of the Ares I while-- simply-- allow the commercial industry to develop rockets and infrastructure for manned access to LEO. The fact that there is currently no private commercial space flight industry in the US didn't seem to concern the commission.
Currently only three government space agencies have the ability to launch and return humans to and from space: the US, Russia, and China. In America's 48 year history of human space flight, they have had 153 successful manned space flights and two fatal accidents [Space Shuttle Challenger (1986), Space Shuttle Columbia (2003)]. The Russians have had 120 successful space flights with two fatal accidents in 1967 and in 1971. China has been very cautious in its emerging manned space efforts-- only launching three manned flights into orbit since 2003.
How safe and reliable private commercial manned space flight companies will be is still an unknown. Space X appears to be the only private company close to developing a manned space flight capability-- principally by emulating the basic space craft designs that government space programs achieved back in the 1960s. So far it has a 60% success ratio as far as it unmanned launches. Still it has plans to attempt to launch humans into orbit sometime during the next decade. Boeing has recently announced that it will join the Bigelow aerospace company in attempting to build a manned space flight capability. How much money a company like Boeing is willing to risk in such a venture should be interesting.
Alternatively, directly shuttle derived rocket designs have once again been proposed that can function as dual purpose vehicles that can launch the new Orion vehicle to LEO or to the Moon with an EDS stage. The Augustine commission has argued that developing the directly shuttle derived rocket boosters could also allow the current space shuttle program to be extended for at least another four years.
NASA is currently spending over $3.4 billion a year on the Constellation program. However, the Obama administration increased the NASA budget by over $900 million for the year 2010, which may perhaps allow $4.2 billion a year in Constellation funding. There are rumors that President Obama may raise the NASA budget an additional $1 billion after he finally announces his agenda for the the US manned space program. And this could give the program $5.2 billion in annual development funding.
If the $3 billion a year Shuttle program is not canceled then that would leave the Constellation program with only $4.2 to $5.2 billion a year in funding. There is the possibility, however, the continuing the shuttle program may only cost $2.5 billion a year. An extra $500 million a year for the Constellation program wouldn't be something to sneeze at. The Orion-CEV is going to cost $1.8 billion a year for at least 5 years plus until it is completed. Program operations and integration may add an additional $1.5 billion annually during the same time period. That leaves only $900 million to $1.9 billion a year for other Constellation expenditures. However, if the Ares I development is canceled, then that leaves us with an additional $1.9 to $2.9 billion a year.
NASA has argued that their directly shuttle derived HLV could be developed for $6.9 billion while proponents of the DIRECT concept have argued that their basic HLV would cost $8.3 billion. NASA has also determined that the cost to develop an EDS stage would cost $2.5 billion and the Altair lunar lander, $4.1 billion. The development of a DIRECT HLV plus EDS and Altair vehicle would therefore cost about $14.9 billion in total. At $1.9 billion a year, over $14.9 billion in funding would it would take nearly 8 years to completely fund such a program. At $2.9 billion a year, these other Constellation programs could be fully funded in less than 6 years. And if there are any delays in any component of the program, then an additional $4.2 to $5.2 billion would be available for every year that program development continues.
However, once the new space vehicles and infrastructure are fully developed, then NASA should have at least $7.2 to $8.2 billion to run its lunar base program plus $2 billion to runs its space station program.
Development of the Ares I/V architectures is much more expensive and takes a lot longer to develop since full funding for the Ares V, EDS, and Altair vehicles doesn't take place until Ares I development is completed. However, by fully funding all the Constellation components simultaneously for the directly shuttle derived scenario, the new space vehicles and infrastructure could be ready in less than a decade.
So my advice to President Obama on his upcoming decision on the future of NASA is to:
1. Increase the NASA budget while keeping the Space Shuttle program going after 2010 until the successor shuttle craft is ready (It will be one of the best domestic and international political investments your administration has ever made!)
2. Cancel the Ares I/V program! Its way too expensive and takes too long to develop
3. Continue the development of the Orion-CEV
4. Choose one of the Directly Shuttle derived concepts (Sidemount or DIRECT) that can be utilized for both the Orion missions to LEO and the ISS and Orion/Altair missions to the Moon.
5. Start fully funding EDS and Altair development immediately along with lunar base modules and other lunar base components. Establishing the first permanent human presence on the surface of another world will be one of the most important developments in the history of humanity that will be remembered for centuries if not millennia by human civilizations both on the Earth and far beyond !
"The knowledge that we have now is but a fraction of the knowledge we must get, whether for peaceful use or for national defense. We must depend on intensive research to acquire the further knowledge we need ... These are truths that every scientist knows. They are truths that the American people need to understand." (Harry S. Truman 1948).