Friday, May 2, 2014

Lowering Costs on the Earth-to-Orbit Run, Preparing for Incoming Asteroids

Getting scared silly by the latest doomsday prediction is silly. So is ignoring real threats.


(Copyright M. Ahmetvaleev, via NASA News, used w/o permission.)

The Chelyabinsk meteor didn't kill anyone. Only 1,100 or so folks needed medical treatment: for injuries ranging from cuts and bruises to a broken spine. Next time, we may not get off so lightly. Now is a very good time to start getting ready for an incoming asteroid.
  1. Launch Vehicles With Legs
  2. Asteroids and Cities: Another Wake Up Call

Learning From Disasters


(From Lester C. Guernsey, via Wikimedia Commons, used w/o permission.)

We've learned a great deal since the 1906 San Francisco earthquake. Even so, the Great Hanshin earthquake in 1995 and the 2011 Tōhoku earthquake and tsunami took 6,434 and 15,885 lives, respectively: probably more in the 2011 disaster. The last I heard, 2,623 people are still missing.

I think controlling earthquakes may be possible: but not any time soon. The forces involved are enormous, and involve large-scale structures deep within Earth.

Preventing asteroid and comet impacts is another matter. Astronomers have started tracking and cataloging assorted debris orbiting the sun, and several methods for deflecting objects headed toward Earth require little or no new technology.

Saving Lives: Ethics, Fear, and Cost

I'm pretty sure that if we develop technology that lets us move asteroids, sooner or later someone will misuse it. Wherever you have people, you have trouble. (Job 5:6-7)

But studying this world and developing new technology is part of being human. It's part of our job. (Catechism of the Catholic Church, 339, 373, 2293-2294, 2402, 2415)

Given a choice between doing nothing, and acting in the hope that lives might be saved: I think action makes sense.

Economics is a factor, of course. A 'planetary defense network' will be expensive. One orbiting observatory will cost about $250,000,000: and that's just to identify incoming objects. Building systems for moving asteroids and comets will not be cheap.

On the other hand, how much would it cost to replace Jakarta, Bangkok, or London?

Looking Ahead


(Reaction Engines Limited/Terra Novus, via Wikimedia Commons, used w/o permission.)
(Reaction Engines Limited's Skylon spaceplane.)

Apart from the Space Shuttle fleet, now out of service, and recoverable capsules like Space-X's Dragon, launch vehicles are still a single-use technology. That makes getting into space very expensive.

A decade from now, we'll probably see shipping rates go down: dramatically, I suspect.

Reaction Engines Limited's Skylon is scheduled for a test flight to the International Space Station in 2019. Quite a few other spaceplanes are in development, including: DRDO/ISRO's Avatar; Sierra Nevada Corporation Space Systems' Dream Chaser.; and JAXA's HOPE-X.

Any one of them may run into insurmountable obstacles and not fly. But I'll be very surprised indeed if none lead to an economical ferry service to orbit.


(From NASA, used w/o permission.)

1. Launch Vehicles With Legs


(From SpaceX, via BBC News, used w/o permission.)
("The triangular features shown here are the legs that deploy just before landing")
"SpaceX rocket stage in 'soft landing' "
Jonathan Amos, BBC News (April 25, 2014)

"SpaceX says its recent experiment to return part of its Falcon-9 rocket back to Earth under control was a success.

"The US company has confirmed that the first-stage of the vehicle launched from Cape Canaveral a week ago used its engines to slow its fall, deployed a set of legs and made a 'soft landing'.

"For safety reasons, the touchdown was actually commanded to take place east of the Cape, far out at sea.

"Nonetheless, the stage was vertical and had zero velocity on contact.

"The company has video of the event - albeit of poor quality - that it plans to post on its website....

"...Potentially, the experiment has enormous significance for the space industry...."
My hat's off to SpaceX for using a routine cargo run to the International Space Station for this test. Experimental equipment on the vehicle must have added to that launch's cost: but surely wasn't as pricey as a separate launch would have been.

Despite recovery efforts, the first stage was lost at sea: but telemetry shows that it worked. That's a good first step.

I think saying that this experiment's potential "has enormous significance for the space industry" is an understatement.

The SpaceX Dragon spacecraft is partly reusable. A reentry capsule gets refurbished after each mission. That's a big step in the right direction: but the rest of the launch vehicle is still thrown away each time the capsule goes up.

But if airlines operated that way, each flight would end with the flight deck and a small storage rack getting attached to a brand new airplane. Ticket and air freight rates would include fractional ownership of a disposable aircraft. Very few folks could afford air travel.

SpaceX: One Step at a Time


(From SpaceX, via BBC News, used w/o permission.)
("This demonstrator shows what a returning stage with legs looks like")
"Traditionally, rockets have been expendable.

"As a vehicle makes an ascent, it dumps propellant stages, which then fall to destruction, torn apart as they tumble end over end."

"SpaceX believes if it can recover those stages and fly them again and again, the cost of access to space could be dramatically reduced.

" 'No-one has ever soft-landed a liquid-rocket boost-stage before,' said SpaceX chief designer Elon Musk. 'I think this bodes well for achieving reusability.

" 'What SpaceX has done thus far is evolutionary, not revolutionary. [But] if we can recover the stage intact and re-launch it, the potential is there for a truly revolutionary impact in space transport costs.'......"
(Jonathan Amos, BBC News)
I enjoyed the way Elon Musk played with ideas and sounds in his 'evolutionary/revolutionary' statement. I also think he's right. SpaceX's Dragon, a reusable capsule, is only a slight advance over earlier launch systems.

Making the other end of the spacecraft, the first stage, reusable, will be another step. After a while, SpaceX may have a completely reusable launch vehicle: some assembly required after each flight, but reusable. If collection, maintenance, and reassembly isn't too costly: the cost savings could be enormous.

Eventually, freighters on the Earth-to-orbit runs may look and act a great deal like the McDonnell Douglas Delta Clipper on its test flights, back in the '90s.

My guess is that if NASA hadn't indulged in on-again/off-again funding while keeping the support crew busy with paperwork, instead of maintaining and testing their vehicle: well, that's another topic.

2. Asteroids and Cities: Another Wake Up Call


(B612 Impact Video 4-20-14 H264 from Spine Films on Vimeo.)
"Asteroid impact risks 'underappreciated' "
Jonathan Amos, BBC News (April 22, 2014)

"A visualisation showing where sizeable asteroids have hit the Earth in recent years has been released by the B612 Foundation.

"The US-based group, which includes a number of former Nasa astronauts, campaigns on the issue of space protection.

"It hopes the visualisation will press home the idea that impacts are more common than we think...."
I rather hope that this "visualization" will help convince decision-makers that preventing a regional disaster may be better than blaming someone after it happens.

I'm in my 60s, so the odds are pretty good that a multi-megaton encounter won't happen while I'm still alive. But I have to think about my kids and granddaughter, too. The B612 Foundation says that an asteroid impact on Earth releasing several megatons of energy happens every hundred years: on average.

That's on average: rocks don't fall out of the sky on a regular schedule. A city-buster may not hit for another thousand years, or tomorrow's news may include speculation about why nobody's heard from Bogotá since Friday evening.

Impossible? I don't think so. It's more likely, though, that the first asteroid-related urban disaster won't involve the destruction of more than a block or so. Small rocks are much more common that big ones.

Besides, the world's cities don't cover all that much of the planet, so the odds are pretty good that the impact would be in the ocean. That might kill a few folks on ships, but would give residents in coastal cities several minutes, maybe a few hours, to run for high ground.

Background: Nuclear-Test-Ban Monitoring and Population Density


(From AP, via BBC News, used w/o permission.)
("The Chelyabinsk impactor was small compared with some asteroids known to have struck the Earth")
"...The presentation leans on data collected by the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO).

"The CTBTO operates a network of sensors that listens out for clandestine atom bomb detonations.

"Between 2000 and 2013, this infrasound system catalogued 26 major explosions on Earth.

"None were caused by A-bombs; they were all the result of asteroid strikes.

"They ranged in energy from one to 600 kilotons. By way of comparison, the bomb that destroyed the Japanese city of Hiroshima was a 15-kiloton device...."
(Jonathan Amos, BBC News)
Quite a few folks are still getting over the shock of what happened in Hiroshima and Nagasaki 69 years back: understandably. Effects of an asteroid impact wouldn't be quite the same: but I think preventing such a disaster is prudent, anyway.


(from en.wikipedia.org/wiki/File:Hiroshima_Damage_Map.png, used w/o permission)

Multiply the Hiroshima bomb by 40, and you've got the the biggest asteroid impact in the last three years. Nobody noticed it, except folks monitoring a test ban treaty: because most of Earth is still essentially unpopulated.


(From U.S. Department of Agriculture, via Wikimedia Commons, used w/o permission.)
(World map: population density in 1994.)

I've lived in central Minnesota for a third of a century, where population density is 25 to 50 people per square mile. I've lived in San Francisco, California, too: where 17,867 people live on every square mile. I don't think San Francisco suffers from "overpopulation," and that's yet another topic.

How Bad Could It Be?

Purdue University/Imperial College, London's Impact Effects calculator gives rough estimates of how much damage we can expect from incoming debris.

It says that a rocky asteroid 23 meters, 75 feet, across hits every 100 years: again, on average.

If this hypothetical asteroid was made of dense rock, it would explode about 177,000 feet up. Fragments would have slowed down quite a bit by the time they hit: at about 6.18 miles per second. Anyone at the impact site would, briefly, know what it's like to get hit by gravel going 22,248 miles an hour.

If the asteroid was of the iron variety, things get more interesting. The airburst would be 7,900 feet up. Folks in a multistory steel frame building near ground zero might have time to get out before the place collapsed. 90% of the trees would be blown down, the rest stripped of leaves and branches. Either way, I wouldn't want to be anywhere near the impact site.

Bigger rocks come less often, but do a lot more damage. We can expect something 95 meters across to hit every 520 years, on average.

If the 95-meter object is made of dense rock, it'll hit Earth's surface as a high-velocity gravel pile: typically in a tight ellipse about 0.6 by 0.8 kilometers. When the crater cools down, it'll be 1.31 kilometers across, and 278 meters deep. That's about 0.8 miles by 913 feet.

If this happens anywhere near a city, there may be some buildings left standing: at least for a while. But between the equivalent of a major earthquake, and winds clocking thousands of miles an hour, the place will be a disaster area.

B612's Sentinel: It's a Start


(From B612 Foundation, via BBC News, used w/o permission.)
("Sentinel would track 90% of Earth-orbit-crossing asteroids larger than 100m, and 50% of the 30m rocks ... B612 says it would give years/decades of notice before any potential impacts with Planet Earth.")
"...A few, people will have heard about, such as the 20m-wide object that ripped across the sky above the Russian city of Chelyabinsk last year.

"But many will have gone unseen because they occurred far out over the oceans.

"And just one of the 26 events was detected in advance, and then by only a matter of hours...."
(Jonathan Amos, BBC News)
Spotting asteroids is far from easy. They're at, well, astronomical distances: very dark, the size of large buildings, and set against a black background. But they can be detected.

B612's Sentinel may be ready by 2018, and will cost around $250,000,000. Don't worry, by the way. Your tax dollars aren't being 'wasted' on this project. As the BBC's Jonathan Amos put it, "the venture is being funded privately through donation."

My guess is that if astronomers found a largish asteroid months before impact, all we could do is start evacuating folks from the impact zone. I'd be astonished if everyone got out in time, but millions of lives could be saved. If we have years to prepare: there's a chance to move the rock, instead. (February 21, 2014)

The BBC article outlines some proposed methods for shoving the city-buster into a safe orbit:
"...Mitigation might be as simple as hitting the asteroid with a heavy block. This nudge would change the velocity of the rock ever so slightly, but if it is done way ahead of time, it should be just enough to make the object arrive "at the crossroads" sufficiently early or late to miss Earth.

"Another "simple" approach being talked about is the so-called 'gravity tractor'. This involves positioning a spacecraft close to a target object and using long-lived ion thrusters to maintain the separation between the two. Because of the gravitational attraction between the spacecraft and the asteroid, it is possible to pull the rock off its trajectory. Relatively straightforward but, again, it requires time to work.

" 'These types of mission are arguably less difficult than building Sentinel. The hard part is finding these things,' says Lu...."
(Jonathan Amos, BBC News)
Developing the technology would be expensive: but would, I think, be worth it in the long run.

I strongly suspect that some if not all of the development cost will be covered by private-sector outfits like Deep Space Industries. And that's yet again another topic. (September 29, 2013; January 25, 2013)


(Deep Space Industries, via Space.com, used w/o permission)

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2 comments:

Brigid said...

Missing an article: "Apart from Space Shuttle fleet, now out of service,"

Think there's supposed to be a plural here: "but would give residence in coastal cities several minutes,"

The Friendly Neighborhood Proofreader

Brian Gill said...

Brigid,

Oops. Found, fixed, thanks!

Definite article - so important, in English is.

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