Saturday, June 30, 2018

Asteroid Day

On June 30 in 1908 the Tunguska object took out a good chunk of forest in Siberia.

In February of 2016 the United Nations approved a resolution stating

30 June International Asteroid Day to observe each year at the international level the anniversary of the Tunguska impact over Siberia, Russian Federation, on 30 June 1908 and to raise public awareness about the asteroid impact hazard

A good time to talk about a project on my wish list. An orbital asteroid devoted to finding  asteroids.

A wide field infrared scope much like WISE. But unlike WISE positioned at SEL1 or SEL2 so the earth isn't a major heat source.

A scope that can make simultaneous observations in visual wavelengths as well as infrared. This would tell us the asteroid's albedo from which we'd get a good estimate of size.

A scope that points towards the inner solar system. For various reasons asteroids within the earth's orbit are very hard to see from earth's surface. An orbital scope pointing towards the inner solar system would give us an inventory of a body of objects we presently know almost nothing about.

I was surprised and pleased to learn such a telescope had already been proposed. NEOCam. Principal Investigator Amy Mainzer.

We're presently getting a pretty good inventory of Chixculub size rocks. But Tunguska sized rocks are much harder to see. And there's a bunch more rocks this size. NEOCam would help us get a better handle on potential city killers.

Another potential NEOCam benefit: It could inventory potential asteroids for mining companies like Planetary Resources or Deep Space Industries.

NASA administrator Jim Bridenstine is enthusiastic about developing space as a source of resources and enabling economic growth.  He's show interest in lunar poles as low hanging fruit.

Near Earth Asteroids are also a low hanging fruit.  If Bridenstine's goal is to expand our economic activity into deep space, NEOCam is a great investment.

A few days ago Marshall Eubanks commented:

NEOCam is not in good shape. Over a year ago it was given one additional year of fairly minimal support. About all that was said about it in this month's SBAG meeting was that it "Continues in extended Phase A" - i.e., on life support.

I hope this changes. We need a telescope devoted to asteroid discovery.

4 comments:

Victor Vasylyev said...

Regarding solving the core problem.
Actually, as follows from published analysis (see, for example: https://cordis.europa.eu/result/rcn/184236_en.html ), three most popular approaches to NEOs hazard avoiding (deflection or disintegration) are not enough effective and not scalable even to country-wide destruction size of space bodies.

The kinetic impact won’t work because of the naturally friable structure of asteroids and comets (due to their extremely heterogeneity and multi-scale porosity) which will prevent shock wave propagation and proper impulse transfer.

The gravitational pull is deficient in that it is extremely weak and further constrained by the NEO’s shape and rotation.

The ultra-high-power nuclear blast scenario is risky and can pose danger both at the ground-based and space-born stages. It can also result in creating a stream containing hundreds of “city-killing” radioactive fragments, e.g., in the case of disintegrating a sub-km asteroid.

It appears that deflecting NEOs by evaporating their material using highly concentrated sunlight is the only method that meets all of the following criteria: scalability up to global-threat NEO sizes, sufficient thrusting power, environmentally friendliness, and low cost.

An improved concept for such solar-based deflection using an innovative concentrating collector was proposed and substantiated in 2013 (see: https://link.springer.com/article/10.1007%2Fs11038-012-9410-2; also a short demo-video: https://www.youtube.com/watch?v=9u7V-MVeXtM ).

Paul451 said...

Victor,
Re: Nuclear asteroid deflection.

The problem with that analysis is that it assumes the only use of nukes is to destroy the asteroid. That would be stupid. The very fact that asteroids are friable means that they act like a shock-absorber. Hence, detonating nuclear devices in sequence at stand-off distance would propel the asteroid like an Orion nuclear pulse drive.

Victor Vasylyev said...

The matter is that shock wave will absorb within the specific asteroid/comet material irrespective to its generation method (contact ram, contactless distance sequence at stand-off, etc.), so the “more weak” weapon-detonating approach will be also not effective, especially at space vacuum.

Paul451 said...

Conservation of momentum says otherwise.