The current estimates of the probability of a damaging impact are based on the historic impact record of Earth and the Moon as well as the catalog of known objects. This is based on real data and statistical rules. To use the Russian Roulette analogy is it better to see if the gun is unloaded for a small amount of money or to make a Kevlar hat using a significant potion of your budget?
Pan-STARRS and ATLAS will get us much better statistics on impact probabilities and sizes over the next few years. Even basic data like size distributions of Asteroids have had large unknowns and estimates have been very uncertain heretofore.
Using ARM to test a gravity tractor is begging the question of the danger of asteroid impacts, it assumes that in the near future there will be one. According to Dr. Binzel the creator of the Torino Scale an asteroid impact which causes local destruction to an inhabited place happens on average of once every 10,000 years. Larger events happen much more rarely. If there is no threat there is no need to develop countermeasures.
ARM will cost at a minimum $1.25 billion and likely much more than that. For a small fraction of that a very intensive search for dangerous NEOs can be done. If that turns up anything bad then the government will effectively write a blank check to deal with it. NASA leadership has been talking about ARM for a while but only recently asked for money to conduct a search. Now they are saying that they don't even need to search because they have already picked the asteroids they want to target from the known catalog. ARM as it is being proposed now will not do the most simple, inexpensive, and important step of asteroid risk mitigation.
Also, the demo is not a significant portion of NASA's budget at all.
What portion of ARM is the gravity capture anyway? isn't it just an additional manoeuvre while holding the selected rock and some measurements?
ARM option B would test out a gravity tractor. As neat as that is what is the chance of devastating impact happening in the next few decades? I am not sure of the wisdom in developing a technology which might not be needed for millennia. Let me posit this though, if the threat of an asteroid impact causes real concern why not use the money to fund something like the B612 Foundation's Sentinel telescope so we could find all the potentially dangerous asteroids? If there is a rock heading at us the most pressing thing is to find it as soon as possible. Funding will materialize for all sorts of deflection strategies in short order.
Quote from: notsorandom on 05/04/2015 06:32 PMARM option B would test out a gravity tractor. As neat as that is what is the chance of devastating impact happening in the next few decades? I am not sure of the wisdom in developing a technology which might not be needed for millennia. Let me posit this though, if the threat of an asteroid impact causes real concern why not use the money to fund something like the B612 Foundation's Sentinel telescope so we could find all the potentially dangerous asteroids? If there is a rock heading at us the most pressing thing is to find it as soon as possible. Funding will materialize for all sorts of deflection strategies in short order.In the run up to World War 2 the Royal Air Force (RAF) prepared to defend Britain from attack by enemy aircraft. Underground control rooms were built to connect the fighter aircraft - Spitfires and Hurricanes - to the string of coastal radar installations. These radars allowed sufficient time to scramble the fighters to intercept the incoming bombers. All 3 parts needed to work for a successful defence.An ARM like spacecraft could be deployed to divert a dangerous incoming asteroid but the asteroid needs to be detected in time. In time is at least 2-3 years before impact.Using the ARM mission times give in http://www.nasaspaceflight.com/2015/04/asteroid-redirect-mission-path-marsDiversion time 6 months (check same for real mission)Flight launch to boulder collection 18 monthsScramble time (To be determined)Total 6 + 18 + TBD = 24 months + TBDTo give Earth those 3 years warning a network of planetary defence telescopes on the Earth and satellites will be needed.Congress is unlikely to allocate the money for the network's construction and operations until presented with the plans and costings. The ARM mission is a proof of concept that can be used to justify building the planetary defence telescopes.
What would it take to add a materials exposure test to the ARM robotic spacecraft? NASA has done similar experiments in the past on the ISS, and is planning something similar on the X-37B: http://www.nasa.gov/press-release/nasa-test-materials-to-fly-on-air-force-space-planeThe point of the ARM variant is that it would gather data for the deep space environment rather than LEO. The idea is that when the astronauts investigate the retrieved boulder, they could also grab the materials exposure experiment and return it to Earth for analysis. Similarly, what would it take to add a solar wind gathering instrument, similar to the one used for NASA's Genesis Discovery mission, to the ARM? The samples from the Genesis mission were somewhat compromised because the return capsule crashed. Again, the idea is that the astronauts would retrieve the experiment while they investigate the retrieved boulder.Not being a spacecraft engineer, I'm imagining these would be fairly simple additions to the mission, just sort of sitting there being exposed to the space environment, not using a lot of spacecraft resources. Reality is probably more complicated, though. Maybe they'd need to be shielded before reaching the asteroid or something like that. How would these additions compare to alternative enhancements to ARM like squeezing in additional instruments to study the asteroid while there in terms of complexity, usefulness, and cost?
May 18, 2015 RELEASE 15-094NASA Seeks Additional Information for Asteroid Redirect Mission SpacecraftNASA has issued a Request for Information (RFI) seeking ideas from American companies for a spacecraft design that could be used for both the agency's Asteroid Redirect Mission (ARM) and a robotic satellite servicing mission in low-Earth orbit.In the early-2020s NASA plans to launch the Asteroid Redirect Mission, which will use a robotic spacecraft to capture a large boulder from the surface of a near-Earth asteroid and move it into a stable orbit around the moon for exploration by astronauts, all in support of advancing the nation's journey to Mars.NASA also has been studying the "Restore-L" mission concept, during which a spacecraft would use dexterous robotic systems to grapple and refuel a government satellite in low-Earth orbit. Restore-L would bring to operational status capabilities needed for future commercial satellite servicing by demonstrating technologies and reducing risk."Today's call for ideas from our industry partners is another important milestone for the Asteroid Redirect Mission, a critical capability demonstration mission that's part of our stepping stone approach for sending American astronauts to Mars in the 2030s," said NASA Associate Administrator Robert Lightfoot. "As part of our acquisition strategy, we're asking for more information toward the ARM spacecraft concept and also on commonality with a notional robotic satellite servicing spacecraft."The RFI is not a request for proposal or formal procurement and therefore is not a solicitation or commitment by the government. Deadline for submissions is 45 days after public posting of the RFI. The full RFI is available at:http://www.nasa.gov/feature/arm-spacecraft-bus-request-for-informationFollowing its rendezvous and touchdown with the target asteroid, the uncrewed ARM spacecraft will deploy robotic arms to capture a large boulder from its surface. It then will begin a multi-year journey to redirect the boulder into orbit around the moon.Throughout its mission, the ARM robotic spacecraft will test a number of capabilities needed for future human missions, including advanced Solar Electric Propulsion (SEP), a valuable capability that converts sunlight to electrical power through solar arrays and then uses the resulting power to propel charged atoms to move a spacecraft. This method of propulsion can move massive cargo very efficiently. While slower than conventional chemical rocket propulsion, SEP-powered spacecraft require significantly less propellant and fewer launches to support human exploration missions, which could reduce costs.This RFI seeks spacecraft designs that may include taking advantage of Xenon capacity SEP, single or multiple component architectures and cost-sharing partnerships.Future SEP-powered spacecraft could pre-position cargo or vehicles for future human missions into deep space, either awaiting crews at Mars or staged around the moon as a waypoint for expeditions to the Red Planet.ARM's SEP-powered robotic spacecraft will test new trajectory and navigation techniques in deep space, working with the moon's gravity to place the asteroid in a stable lunar orbit called a distant retrograde orbit. This location is a suitable staging point for astronauts to rendezvous with a deep space habitat that will carry them to Mars.Before the large asteroid boulder is moved to lunar orbit, NASA will use the opportunity to test planetary defense techniques to inform mitigation of potential asteroid impact threats in the future. The experience and knowledge acquired through this operation will help NASA develop options to move an asteroid off an Earth-impacting course, if and when that becomes necessary.NASA's Near Earth Objects Program continues to implement new capabilities and upgrades to existing projects for detecting and cataloging asteroids. The agency also has engaged non-traditional partners and the public in the hunt for undetected asteroids through the NASA's Asteroid Grand Challenge activities, including prize competitions. In March, the agency announced the release of a software application based on an algorithm created through a NASA challenge that has the potential to help increase the number of asteroid detections in collected sky images.For more information about NASA's Asteroid Initiative, visit:http://www.nasa.gov/asteroidinitiativeFor more information about NASA's robotic satellite servicing capabilities office, visit:http://go.usa.gov/3kpV5