新的“決策地圖”可以幫助我們選擇保護(hù)地球免受小行星撞擊的最佳任務(wù)

新的“決策地圖”可以幫助我們選擇保護(hù)地球免受小行星撞擊的最佳任務(wù)

Near-Earth asteroids are a serious risk for humanity as we still know little about these objects and their properties. Strategies and tabletop exercises have been employed over the last few years to make us more prepared, and researchers have now produced an interesting tool that could be used as well.

近地小行星對(duì)人類(lèi)來(lái)說(shuō)是一個(gè)嚴(yán)重的威脅，因?yàn)槲覀儗?duì)這些天體及其特性知之甚少。在過(guò)去的幾年里，我們一直在使用一些策略和桌面練習(xí)來(lái)讓我們做更多的準(zhǔn)備，研究人員現(xiàn)在已經(jīng)開(kāi)發(fā)出一種有趣的工具，也可以使用。

Alfredo Carpineti

Soon to be reported in Acta Astronautica, engineers from the Massachusetts Institute of Technology (MIT) have created a decision map tool to help us decide what’s the best mission to employ when dealing with potentially risky asteroids. The idea particularly focuses on ensuring asteroids avoid gravitational keyholes, small regions of space where a planet’s gravity can turn a risky asteroid into a planet-killer.

不久將在《宇航學(xué)報(bào)》上報(bào)道，來(lái)自麻省理工學(xué)院(MIT)的工程師們創(chuàng)建了一個(gè)決策地圖工具，幫助我們決定在處理有潛在風(fēng)險(xiǎn)的小行星時(shí)采用的最佳任務(wù)是什么。這個(gè)想法特別關(guān)注于確保小行星避開(kāi)重力鎖孔，即一個(gè)行星的重力可以將一個(gè)危險(xiǎn)的小行星變成行星殺手的小空間區(qū)域。

“People have mostly considered strategies of last-minute deflection, when the asteroid has already passed through a keyhole and is heading toward a collision with Earth,” lead author Sung Wook Paek, a former graduate student in MIT’s Department of Aeronautics and Astronautics, said in a statement. “I’m interested in preventing keyhole passage well before Earth impact. It’s like a preemptive strike, with less mess.”

該研究的主要作者、前麻省理工學(xué)院航空航天系研究生Sung Wook Paek在一份聲明中說(shuō):“當(dāng)小行星已經(jīng)穿過(guò)一個(gè)鑰匙孔，正朝著與地球相撞的方向前進(jìn)時(shí)，人們通常會(huì)考慮最后一刻偏離軌道的策略。”“我對(duì)在地球撞擊之前防止鑰匙孔通過(guò)很感興趣。這就像先發(fā)制人，減少了混亂。”

Acting in advance could be crucial and that’s where the framework kicks in. Missions to deflect an asteroid will have to deal with a lot of uncertainties regarding their target. The asteroid’s mass, composition, and momentum all need to be known if we are to shift its orbit away from Earth. But this might not be possible and the missions might have to be launched with significant unknowns, some of which could lead to failure and have deadly consequences.

提前行動(dòng)可能是至關(guān)重要的，這就是框架發(fā)揮作用的地方。使小行星偏離軌道的任務(wù)將不得不處理有關(guān)其目標(biāo)的許多不確定性。如果我們要把小行星的軌道從地球移開(kāi)，就必須知道它的質(zhì)量、組成和動(dòng)量。但這可能是不可能的，而且發(fā)射任務(wù)可能會(huì)有重大的未知因素，其中一些可能會(huì)導(dǎo)致失敗和致命的后果。

“Does it matter if the probability of success of a mission is 99.9 percent or only 90 percent? When it comes to deflecting a potential planet-killer, you bet it does,” co-author Professor Oliver de Weck of MIT added. “Therefore we have to be smarter when we design missions as a function of the level of uncertainty. No one has looked at the problem this way before.”

“任務(wù)成功的概率是99.9%還是只有90%，這有關(guān)系嗎?”麻省理工學(xué)院的奧利弗·德·韋克教授補(bǔ)充道。“因此，當(dāng)我們根據(jù)不確定性水平設(shè)計(jì)任務(wù)時(shí)，我們必須更聰明。以前從來(lái)沒(méi)有人這樣看待這個(gè)問(wèn)題。”

The team considered three scenarios for potential missions. The first involves sending a kinetic impactor probe, a spacecraft that will crash into the asteroid to push it off its course. The second sends a scout mission to measure the asteroid followed by a kinetic impactor. The third has two scouts, one to measure the asteroid and one to push the asteroid slightly off course, followed by the major kinetic impactor.

該小組考慮了可能的任務(wù)的三種情況。第一種方法是發(fā)射一個(gè)動(dòng)能撞擊探測(cè)器，即一艘宇宙飛船撞擊小行星，使其偏離軌道。第二次發(fā)射了一個(gè)偵察任務(wù)來(lái)測(cè)量小行星，隨后是一個(gè)動(dòng)力沖擊器。第三個(gè)探測(cè)器有兩個(gè)，一個(gè)用來(lái)測(cè)量小行星，另一個(gè)用來(lái)把小行星稍微推離軌道，接著是主要的動(dòng)能沖擊器。

The team plugged properties of real asteroids into their simulations, such as 99942 Apophis, which will fly very close to Earth in 2029 and then again in 2036. In their framework, they saw that if Apophis were going to pass near a gravitational keyhole in five years or so, there would be enough time to send the two scouts followed by the impactor. If this were to happen just two to five years in the future, the second scenario is preferable. Any sooner than that and things get very troubling. The kinetic impactor alone might not be enough to push the asteroid away.

研究小組將真實(shí)小行星的特性加入到他們的模擬中，比如阿波菲斯99942，它將在2029年飛離地球很近，然后在2036年再次飛離地球。在他們的研究框架中，他們發(fā)現(xiàn)，如果阿波菲斯在5年左右的時(shí)間內(nèi)通過(guò)一個(gè)引力鎖眼附近，就有足夠的時(shí)間讓兩個(gè)偵察兵跟著這個(gè)撞擊者。如果這種情況只在兩到五年后發(fā)生，那么第二種情況會(huì)更好。如果早于此，事情就會(huì)變得非常麻煩。單靠動(dòng)能沖擊器可能不足以把小行星推開(kāi)。

The work is very interesting but assumes that we will be aware of asteroids well in advance and that we are ready to launch a mission at the drop of a hat. This might not be the case in real life.

這項(xiàng)工作非常有趣，但前提是我們要提前知道小行星的存在，并隨時(shí)準(zhǔn)備執(zhí)行任務(wù)。在現(xiàn)實(shí)生活中可能不是這樣。