I’ve written about the risk posed by the potential impact of a Near Earth Object on this planet several times within these Space Sunday articles. While they are rare, as we’ve seen with the Tunguska event of 1908, and the more recent 2013 Chelyabinsk air-blast and 2018 LA (ZLAF9B2) in June 2018, objects of a size sufficient enough to survive their initial entry into the Earth’s atmosphere before being ripped apart in a violent explosion can and do exist.
Nor is Earth alone in the threat – as witnessed by those observing the lunar eclipse of January 21st, 2019, the Moon can be hit as well. At 04:41 GMT, during the period of totality during that eclipse, numerous astronomers in North and South America and in Western Europe saw a sudden bright flash lasted less than 1/3 of a second. It was later attributed to an object around 30 to 60 centimetres (1 to 2 ft) across striking the Moon at around 61,000 km/h, producing a new crater somewhere between 10 and 15 metres (32 to 49 ft) across.
While the majority of the 10+ million objects thus far found crossing Earth’s orbit as they go around the Sun pose no real threat to us (in fact, the number of Potentially Hazardous Asteroids, or PHAs, has been put at just 2,000), and the risk of a substantial impact occurring in anyone’s individual lifetime is relatively remote, the fact is that – as Douglas Adams famously noted – space is big really big. Even the solar system is a vast place when compared to the size of Earth, big enough to hide any number of objects that might one day pose a very real threat to all life on Earth or, given humanity’s global distribution the potential to place one of our major cities at risk.
So how might we deal with such an eventuality? Currently, there are really only three practical options available to us – although others have been suggested, and more might be developed in the future. Which of them might be used depends on how much lead time we have in which to take action. To summarise:
- The gravity tug: if the impact is decades away, a spacecraft with a motor such as an electric ion drive could rendezvous with the asteroid and enter a halo orbit around it. The motor could then be fired along the axis of flight, allowing the gravitational influence of the vehicle to “pull” the asteroid onto a new course. However, this option can really only be used if the inclination of the threatening asteroid is relatively close to that of Earth’s; if the two are very disparate, the time needed to get the spacecraft to the asteroid using gravity assist manoeuvres around the Earth or Venus or even Jupiter, might simply be too long.
- The Kinetic intercept: this uses brute force to deflect the asteroid by slamming relatively solid masses into to, their momentum serving to shunt it into a slightly altered orbit around the Sun that is sufficient for it to miss the Earth.
- Nuclear deflection: similar to the kinetic intercept, but uses the shock waves of nuclear weapons detonated close to the asteroid to again shunt it into an altered orbit so it misses the Earth.
The major problem with the last two is the risk that if the asteroid is too fragile, rather than shunting it aside, they could shatter it, leaving Earth facing not s single object, but a scatter gun of debris, potentially with multiple elements large enough to devastate large areas of the planet’s surface should they enter the atmosphere and explosively disintegrate. This is also the reason why trying to directly blow an asteroid part using a nuclear strike isn’t regarded too favourably. There are other issues with each of these options that could also limit their effectiveness, or raise the need to repeat them, but they provide a general idea of how we might react.
Hence why the International Academy of Astronautics holds a Planetary Defence Conference every two years to discuss the latest findings with NEO and PHAs, and the ways and means to prevent such an impact – or at least the loss of life minimised. Since 2013, the 5-day conference has included a special “war game” type simulation to examine how a threat might be dealt with, and at the 2019 conference, held between April 29th and May 3rd, the simulation with publicly disseminated via social media as it progressed, to encourage grater public understanding about the need to better locate and track NEOs and PHAs (which are currently being discovered at the rate of around 700 a year).
In this simulation, which compressed an 8-year time frame into 5 days, the 200 astronomers, engineers, scientists and politicians at the conference were informed a large (fictional) asteroid around 300 metres across would slam into Colorado in 2027, unless then managed to divert it. Initially, things went well: a joint mission involving the USA, Russia, Europe, China and Japan used kinetic impacts to safely divert the bulk of the asteroid away from Earth. However, a 60m fragment broke away on a course that would see it hit the Earth’s atmosphere at 69,000 km/h (43,000 mph) and explode 15 km (9.3 mi) above Central Park, New York City. The force f the air blast would be sufficient to complete raze Manhattan and parts of New York City for a radius of 15 km (9.4 mi), with the effects of the blast felt up to 68 km (42.5 mi) from the epicentre. Plans were drawn up to try to deflect this fragment using a nuclear blast, but these became mired in political wrangling (not for the first time in these simulations) until it was too late to achieve the desire deflection.
While such exercises might sound like scientists playing games, they do serve a purpose in that they help to underline the massive threat we face if we discover an asteroid is on a collision course with Earth – and the need for us to have better means to detect objects that might pose a threat early enough that we can take action, and also to better understand the processes – technical, scientific and political – that need to followed / overcome in order to prevent a collision.
They also highlight other issues as well. In this case, just how do you handle evacuating a city of 8 million souls? How much time is required (in the simulation, it came down to just 2 months)? What are the logistics required to ensure a (relatively) smooth evacuation? How and when should you tell the public? How do you avoid mass panic? This type of discussion is actually of major import, given current thinking is that if an object due to strike the Earth is 60 metres or less across, the focus should be on evacuating the area directly affected, rather than on trying to deflect it.
One asteroid that will not be striking Earth in the immediate future is 99942 Apophis. It will, however, be making a very close fly-by on April 13th, 2029, when it will hurtle past us at just 31,000 km (19,000 mi) – closer than some of our own satellites orbiting Earth.
At 340m across, Apophis is bigger than the simulated asteroid featured in this year’s IAA Planetary Defence Conference. It was first identified in 2004, when it was given a 2.7% chance of impacting with Earth in 2029. Additional data later eliminated that risk, together with a possible impact in 2036. however, there is still a 1 in 150,000 chance it may hit us in 2068.
As it is, the 2029 close pass offers scientist the opportunity to observe the asteroid up close without the need for space missions, and plans are already being drawn up to do precisely this, using optical and radio telescopes to gather as much information as possible on the asteroid – including precisely how such a close encounter with Earth’s gravity affects its orbit, something that will allow its future close passes including that of 2068 – to be modelled with even greater accuracy. In addition, the data gathered could be of significant value in determining how asteroids of a similar size and composition to Apophis might be deflected in the future, should one ever pose a real threat.
New Shepard Flies Ahead of Anticipated Announcement
Thursday, May 2nd saw the latest flight of Blue Origin’s sub-orbital vehicle, New Shephard. It marked the 11th successful flight of the system, as the company moves closer toward starting sub-orbital flights with fare-paying passengers.
The flight lifted-off from the company’s West Texas launch facility. After lifting the capsule section to altitude, the booster – making its fifth flight – separated and returned to the launch pad to perform a successful landing 7.5 minutes after launch. The capsule continued upwards in a ballistic arc, carrying 38 micro-gravity science experiments into sub-orbital space, 9 of them supported by NASA, before returning to a landing under parachute.
The NASA-sponsored payloads included a 3D-printing experiment led by the University of Kentucky, which could help advance off-Earth manufacturing technology; a centrifuge operated by the company NanoRacks that could allow researchers to gather biological data on suborbital missions; and a Purdue University experiment designed to improve measurements of the fuel remaining in deep-space spacecraft’s tanks.
We are now on the verge of giving students and teachers the ability to build and fly affordable experiments in space. When teachers are this excited about putting experiments in space, their students can’t help but get excited about space, too. It’s such a huge milestone. This opens the door to flying more experiments for more schools, and that means exposing more teachers and students to the promise of space flight.
– Elizabeth Kennick, president of Teachers in Space, referencing the experiments
flown on New Shephard 11 from educational centres
Blue Origin remains tight-lipped on when passenger-carrying flights with New Shephard will commence, but carrying science payloads very much forms a part of its overall purpose, and so launches such as NS11 aren’t simply publicity stunts; they serve a genuine scientific purpose.
The NS11 launch renewed speculation on the nature of an April 26th tweet from Blue Origin suggestive of a major announcement is to be forthcoming, potentially on May 9th, 2019.
The tweet features an image of the Endurance, the “luxury ice-capable steam yacht” which, following its construction, was purchased by Ernest Shackleton for his 1914 Imperial Trans-Antarctic Expedition. Given without any context other than what appears to be a US-format date 5.9.19, particularly raised speculation the Blue Origin might be accelerating some of its other ambitions.
In particular, in 2017 Blue Origin’s Founder, Jeff Bezos, indicated the company had lunar aspirations and would be developing the capability to go to the Moon “Amazon style” – delivering the cargo and material astronauts will require to establish a base there. To achieve this, Blue Origin is developing their New Glenn 2-stage orbital “heavy lift” vehicle and a cargo lander called Blue Moon, capable of delivering up to 4.5 tonnes of equipment to the lunar surface.
What’s interesting about this is that in talking about these aims, Bezos pointed to Shackleton crater close to the Moon’s south pole as a potential destination, place where water ice is believed to exist within the permanently shadowed floor of the crater. He’s also voiced strong support for both NASA’s aims to return humans to the Moon and the European-mooted idea of a lunar village.
Thus, the reference to the Endurance has been taken by some to indicate Blue Origin might mak a significant announcement about its lunar aspirations on May 9th, either directly in reference to the Shackleton Crate idea, or possibly in support of NASA’s accelerated programme to return humans to the Moon by 2024. I’ll hopefully have more on this in my next Space Sunday update.
SpaceX Crew Dragon Test Vehicle Loss Confirmed
Senator Richard Shelby, chairman of a Senate committee that manages NASA’s budget, has stated that the “anomaly” SpaceX experienced during an ground-based test of a Crew Dragon test vehicle’s launch abort motors on April 20th, 2019 (see Space Sunday: Moon, Mars, and abort systems) did result in the complete loss of the capsule.
The test saw the vehicle due to take part in a full flight test of the abort system in June 2019, mounted on a stand at the SpaceX test facility in South Texas for a series of firings of its launch abort system motors. It’s not entirely clear what happened, but at some point in the test, an “anomaly” occurred, although NASA and SpaceX had remained tight-lipped about what happened, or the state of the test vehicle.
Shelby made his statement after receiving an update on the joint investigation into the accident that NASA is conducting with SpaceX. Coincidentally, on May 1st, not long after Shelby made his remarks, a video was leaked via Twitter purportedly showing the capsule exploding – and NASA inadvertently confirmed the footage was from the April 20th test.
Exactly how this will affect Crew Dragon flights is unclear. Following the June in-flight testing of the launch abort system, SpaceX had been due to complete Demonstration Mission 2, flying two NASA astronauts to the International Space Station in late summer 2019. This flight was intended to pave the way for “operational” flights carrying crews to and from the ISS commencing. Clearly, there will be no further Crew Dragon flights until after the cause of the April 20th explosion are known, and possibly not until any required remedial actions needed to prevent any recurrence of event have been taken.