lt’s the size of Texas, Mr President.

At one point in the future we’ll be faced with a threat from an asteroid coming our way. Hopefully we’ll know about it long before it’s even close to Earth. What in your opinion is the best way to redirect an asteroid using current or future technology?
Andrew Rader (SpaceX engineer, MIT PhD, author)

I have a video about that:

The larger an object is and the faster is it moving, the more momentum and kinetic energy it has. Large objects moving in space are nearly impossible to stop, but if detected early enough, they can be deflected. Just a infinitesimal course correction can have a major effect on an object's trajectory months or years down the road. The key is to nudge the path of an asteroid early enough so that it grazes peacefully past our planet. Even simple things like painting an asteroid with absorbing or reflecting paint changes modifies the effect of solar rays, and could help steer the asteroid clear of disaster. Alternatively, you could attach a solar sail or small efficient engine. The key to any solution is early detection.

Antonio Paris (Astronaut Candidate, Astronomy Professor, Planetary Scientist, Space Science Author)

Every year, astronomers discover new asteroids in the Solar System. Current and past Near Earth Objects (NEO) programs, such as the Catalina Sky Survey (CSS) and The Minor Planet Center (MPC), currently use optical telescopes at high altitude with thermo-electrically cooled cameras. These methods require dark skies with a high transparency, extended camera exposure times, and image data processing. Although the entire process is cumbersome, these surveys have been responsible for detecting and discovering hundreds of asteroids in our Solar system. Recently, Congress signed the NASA Transition Authorization Act of 2017, which directed NASA to expand the NASA Near Earth Object program to detect, track, catalog, and characterize potentially hazardous NEOs less than 140 meters. The act, moreover, leverages the capabilities of the private sector and philanthropic organizations to the maximum extent practicable in carrying out the NEO Survey Program. Asteroid impact events, specifically on Earth, have played a major role in the evolution of the Solar System. These events have shaped the history of our planet and numerous theories suggest that an impact from an asteroid formed the Moon, shaped life on Earth, and caused at least 5 mass extinction events on Earth. These private and public asteroid detection programs, however, are not responsible for redirecting an asteroid that could impact Earth nor do we have the current capability to do so.

NASA’s Planetary Defense provides several mitigation strategies to prevent an asteroid impact – but none of the proposed strategies have not materialized into anything other than blueprints. Nonetheless, there is a noteworthy piece of information that, according to NASA, is required prior to attempting an asteroid redirect mission: “changing the velocity or trajectory of the object by less than an inch per second years in advance of the predicted impact”. In the past 50 years, a variety of proposals have recommended several approaches to stopping or redirecting an asteroid from impacting Earth. Some of these include the use of nuclear weapons to destroy the asteroid, towing the asteroid away by using gravity or a cable, or landing a robot on the asteroid, which would them use propulsion to slightly move the asteroid into a different trajectory. Unfortunately, we currently do not have the technology to advance any of these proposals or motivation from Congress to spend billions or trillions of dollars to develop them.

The possibility that one day another asteroid will impact Earth is mathematically probable. The best-case scenario is that we would detect the asteroid well in advance for NASA or the private space industry to develop one of these programs to stop it. Personally, of all the proposals, my choice to stop the asteroid would be the gravity tractor, as proposed by NASA. If we could detect the asteroid years in advance, the asteroid’s path could be changed by using the gravitational pull of a spacecraft. The spacecraft, which could be launched from the Moon, would travel alongside the impactor for several years and gently pull it out of Earth’s path. The spacecraft, moreover, could be controlled remotely from Earth or the Moon and thus provide the best solution against Earth impact event.

Fraser Cain (publisher at, co-host of Astronomy Cast)

The bottom line is that we just don't know. Maybe it'll be by shooting a laser at it? Or maybe by detonating a nuke near it? Or putting a railgun on it and blasting out material. Until we have the commitment and courage to send a mission to an asteroid and practice some of these different techniques we won't truly know the best way to redirect them.

Episode 1 – Science Outreach

In our first episode I’m joined by two of our panelists: Andrew Rader and Mike Simmons. We cover the topic of public science outreach and the challenges it faces.


Astronomers Without Borders

Andrew Rader’s website


Host: Mateusz Macias

Music: Kedenna

If you have any questions, comments or feedback please us a contact form on our website or send a message to If you like our podcast leave us a review on itunes, stitcher or your podcast app. You can also support us on Patreon at Music was provided by Kedenna and is used with permission.

Win “Mars Rover Rescue” competition – question 5 of 5

Question 5/5:
What is the name of the first book published by Andrew?

Answers can be posted in the comment section to this post, sent via direct message to Astronomy/Finest twitter account, posted as a comment to tweet containing details of new questions or sent to

Win “Mars Rover Rescue” competition – question 4 of 5

Question 4/5:
What is the name of the Discovery Channel series that Andrew was a winner of?

Answers can be posted in the comment section to every post (Blog), sent via direct message to Astronomy/Finest twitter account or posted as a comments to tweets containing details of new questions.

Prepare for warp speed

Science fiction has shown us spaceships travelling at enormous speeds, some of them had faster-then-light capabilities (and some have done the Kessel run in 12 parsecs). Which metods of transportation that are being developed or thought about in the near/far future you think are the most promising?
Paul Carr (Space Systems engineer at NASA, podcaster, blogger, investigator)

I'm not optimistic about faster than light travel at any time in the future, although I would love to be proved wrong. Not only do we not have the technology to travel faster than the speed of light, we don't know what technology we need, or even if it's possible.

For the near future, something we could make happen would be nuclear space propulsion - first fission reactors, and then fusion reactors. My dream reactor would be a Helium 3 fusion reactor. Helium 3 is stable, and the Helium 3 fusion reaction produces Helium 4 (also stable), a proton (or two) (that can be used to generate electric power), and energy, but no neutrons. Neutrons are a problem that make most fusion reactors unusable for space applications. Such a reaction is far more mass efficient than chemical rockets, and with some work, could open up the entire solar system to us.

Fraser Cain (publisher at, co-host of Astronomy Cast)

In the near term, I'm mostly excited about the potential for light sails, like the Breakthrough Starshot. If this technology can be developed, we could see spacecraft traveling out to Pluto within a few weeks or even days. Once we've mastered this tech, we can start sending spacecraft out to other stars.

Ciro Villa (technologist, application developer, STEM communicator)

Ever since human have been able to use their imagination they have been dreaming of traveling far away in space to explore and discover new worlds. Unfortunately, as much as our brains can dream it, we are limited by our physical and technological capabilities to only be able to travel very nearby.

So far in the history of space travel, chemical rockets have been the main mean of propulsion and other new propulsion technologies are only at their infancy. Many studies are underway and much literature has been created to envision the design of new ways to propel human made spaceships further in space and in shortest amount of times. In the shortest term, more efficient forms of propulsion are being developed such as electric variants like Ion, Plasma and Hall-effect thrusters some of which are already operational on some space crafts ( Also, Solar sails which are still somewhat experimental in nature with their size challenges and limitations, are being investigated as another promising mean to accelerate spaceships beyond the confines of our Solar System.

More futuristic forms of propulsion are unfortunately still only on paper at this time and it will take willpower, new discoveries, money, time or most likely all the above to be further developed. The hope is that with the accelerating pace of technological advancements, some of these new, exotic propulsion technologies will materialize at some point in our future make human exploration of deep space a reality.

Andrew Rader (SpaceX engineer, MIT PhD, author)

For faster than light travel, it's always possible that there will be some breakthrough that we can't anticipate. Apart from that, I think we're going to end up taking a long time to get to other stars, possibly in some kind of suspension or by just sending robots or human embryos. In terms of advanced propulsion in general, anti-matter offers the best mass to energy ratio we know of, but that's a long way off (hundreds of years?). Fusion rockets might be possible before the end of the century. These would be great for travel in the solar system, but probably not to another star.

Robert Novella (co-founder and vice-president of New England Skeptical Society, co-host of Skeptics’ Guide to the Universe)

Chemical rockets have served humanity very well for many decades. They have launched satellites into orbit and blasted our probes and landers into the nooks and crannies of our solar system. They have lifted humans to low earth orbit and our moon. All of this has given us a priceless cornucopia of images and data and mind-boggling discoveries.

These types of rockets however are not nearly as adept at ferrying our fragile bodies much beyond the moon. To keep us healthy and happy requires vast ships that are prohibitively slow and expensive for trips to the closest practical planet, Mars.

Luckily, conventional rockets are only a tiny subset of all rocket types, yet I've been disappointed for literally decades that we have made so little progress on other types of rocket technology for transporting humans.

I'm still holding out hope for the widespread realization that rockets using nuclear fuel are the only real option we have in the near future for getting humans well past our moon. The energy density of nuclear is orders of magnitude that of chemical energy. Nuclear thermal rockets using fission for example could weigh half as much as similarly powerful chemical rockets. Directly comparing chemical vs nuclear rockets is complex but many have concluded that such nuclear rockets would be at least as twice as efficient as chemical rockets. This would allow trips to mars requiring half the time, or less, which is especially important considering the more time spent in space, the more time you're exposed to life-threatening solar radiation and cosmic rays. Fission rockets would also allow for some serious maneuvering during a flight which is too expensive for modern chemical engines. You're just not much of a spaceship in my book if you can't maneuver easily.

A little beyond these fission rockets (which we can build now), we will create fusion rockets which should quickly predominate since they are even more efficient and produce less radioactive waste. Remember, a significant limitation to any ship's maximum velocity is the amount of fuel required to reach that velocity. You could actually reach 10% of the speed of light with chemical engines but you'd need a gas tank the size of our sun to do that. Doable? Yes, theoretically. Practical? Ummm, no. Fission would require far less fuel to reach that speed and fusion even less. So what would require the least amount of fuel? Read on...

Long-term scenarios for Space Travel will certainly offer humanity many fascinating hi-tech options but some type of antimatter engines will probably be required if you want to move something space ship sized as close as possible to the speed of light. Sure, there may be some bizarre quirk of physics that allows for superluminal travel but...probably not, so don't get your hopes up.

We know for certain right now that as you approach appreciable fractions of the speed of light, your mass starts increasing alarmingly fast (kinetic energy). To continue accelerating, your ballooning mass requires an exponentially increasing amount of energy. Eventually, to reach the speed of light itself you'll need infinite energy to move your infinite mass. Unless you have infinite energy in your back pocket, you'll never hit that speed.

To get as close as possible however, you'll need an efficient method of energy conversion and that's exactly what matter/antimatter annihilation provides. The energy released from such interactions is truly huge even if the masses involved are tiny (that is, after all, a key take-away from E=mc^2). The primary problem though is that we can't practically convert all the byproducts of matter/antimatter collisions into the kinetic energy of our spaceship. The bottom line then is that we will probably not be able to ever get arbitrarily close to the speed of light. The estimates seem to be all over the place but somewhere between 40 and 70 percent of the speed of light could be attainable eventually.

I'm totally ok with a spaceship going 753 million km per hour.

Antonio Paris (Astronaut Candidate, Astronomy Professor, Planetary Scientist, Space Science Author)

For generations, science fiction has attempted to shape our future. From cameras on a watch as depicted in Dick Tracy; to warp speed, a common mode of travel used extensively in the Star Trek franchise. However, traveling faster than the speed of light or at warp speed, from a practical purpose, is not possible according to the laws of physics. The energy required to achieve the speed the speed of light, for example, would be infinite – sort of a an impossibility.

Today, and for the foreseeable future, spacecraft are limited to local orbits and interplanetary missions. There are numerous factors that shape spacecraft design and capabilities, but predominantly they are due to budget constraints, its intended function, and policy requirements. Extraordinary specific power and the ratio of jet-power to total spacecraft mass are required to reach interstellar targets within sub-century time frames. Some heat transfer is unavoidable and a tremendous heating load must be effectively handled. Thus, for interstellar rocket concepts of all technologies, a key engineering setback is controlling the heat transfer from the exhaust stream back into the spacecraft.

Based on research in the late 1950s to the early 1960s, it is technically possible to build spacecraft with nuclear pulse propulsion engines (i.e. driven by a series of nuclear explosions). This propulsion system contains the prospect of very high specific impulse and high specific power. This type of spacecraft, in my opinion, is our best hope for achieving interstellar travel.

In 1968, Project Orion team members proposed an interstellar spacecraft using nuclear pulse propulsion, which used pure deuterium fusion detonations with a very high fuel burn-up fraction. They calculated an exhaust velocity of 15,000 km/s and a 100,000-ton spacecraft able to achieve 20,000 km/s allowing a flight-time to Alpha Centauri of roughly 130 years. Later studies suggested that the top cruise velocity that can theoretically be achieved by a Teller-Ulam thermonuclear unit powered Orion spacecraft, supposing no fuel is saved for slowing back down, is about 8% to 10% of the speed of light. An atomic Orion can reach perhaps 3%-5% of the speed of light. A nuclear pulse drive spacecraft powered by Fusion-antimatter catalyzed nuclear pulse propulsion units would be comparably in the 10% range and pure matter-antimatter annihilation rockets would be theoretically capable of achieving a velocity between 50% to 80% of the speed of light.

In closing, although there have been numerous proposals and design concepts, spacecraft propulsion for interstellar flight is not an easy endeavor or economical. At current pace, we are at least hundreds or perhaps thousands of years before capable of interstellar travel to even the closest stars. Nevertheless, there are no doubts we will become an interstellar species in the foreseeable future.

Win “Mars Rover Rescue” competition – question 3 of 5

Question 3/5:
What is the name of Andrew’s “build-you-own animal” game?

Answers can be posted in the comment section to every post (Blog), sent via direct message to Astronomy/Finest twitter account or posted as a comments to tweets containing details of new questions.


Win “Mars Rover Rescue” competition – question 2 of 5

Question 2/5:

In what year did Andrew Rader began working for SpaceX?

Answers can be posted in the comment section to every post (Blog), sent via direct message to Astronomy/Finest twitter account or posted as a comments to tweets containing details of new questions.

How to win “Mars Rover Rescue” – question 1 of 5

Question 1/5:
“Mars Rover Rescue” is a second part in series of adventures of Giraffestronaut MC Longneck. What’s the name of the first book?

Answers can be posted in the comment section to every post (Blog), sent via direct message to Astronomy/Finest twitter account or posted as a comments to tweets containing details of new questions.

5 quickest answers to each question will earn points – 5 points for the quickest answer, 4 points for second quickest and so on.

How to win Andrew Rader’s “Mars Rover Rescue”

5 questions about Andrew Rader (his work and his activities) will be posted on the blog. 5 quickest answers to each question will earn points – 5 points for the quickest answer, 4 points for second quickest and so on. Person with the most points after fifth question will win Andrew Rader’s book “Mars Rover Rescue” (paperback version if the winner is located in the US, digital version if outside of US).

Details about the questions will be posted on the blog’s Twitter profile (

Answers can be posted in the comment section to every post (Blog), sent via direct message to Astronomy/Finest twitter account or posted as a comments to tweets containing details of new questions.

First question: 09.05.2017, 16:00 EDT.

“Life, but not as we know it” by Andrew Rader

Earth is quite a lovely little rock in space. While there is no doubt that at least most of our planet supports ideal conditions for human life, and Earth is the most “habitable” world we know of, this doesn’t necessarily mean that Earth is a member of an exclusive a club. It’s not that we magically dropped down out of the sky onto a planet that happened to be perfect. The reality is that our line of organisms has been shaped by billions of years of evolution on this planet. Earth seems so amazingly habitable to us not by happenstance, but precisely because we evolved to thrive in its environment.

Lots of types of worlds may support many types of life, but not necessarily life as we know it. There are of course certain bounds and limits. So far as we know, there must be a temperature range capable of supporting chemical reactions of stable organic molecules, and (we think) some sort of liquid. Water is ideal, but may not be the only liquid capable of serving this purpose. For example, the surface of Saturn’s moon Titan is covered in liquid hydrocarbons at a chilly -180°C (colder than liquid nitrogen). We can’t rule out the possibility of microorganisms or even sizable animals living in this environment, albeit with very un-Earthlike chemistry, relying on a methane cycle not so different from our planet’s water cycle. Perhaps small crystalline “sea snakes” glide through the freezing waters of Titan. 

Life on Earth thrives across an extremely wide array of conditions, and this would be no different from other worlds. Bacteria on Earth live essentially everywhere from the upper atmosphere to the depths of Earth’s crust. They survive extremes of radiation exposure, high and low pressures and temperatures, abundance or lack of light, and utter deprivation of water and nutrients. The live in the thermal pools of Yellowstone National Park at temperatures up to 80°C, dining on a rich array of chemicals leaking from volcanic vents. Microorganisms have been found deep underground in oil wells, and suspended in lakes of liquid water trapped miles under the Antarctic ice sheet. In fact, there’s more life underneath our planet than on top of it. Bacteria live miles underground, never seeing light and consuming nothing but chemicals stored in rocks. There might be as many as a hundred trillion tons of bacteria living beneath our feet. Pile up all the underground bacteria, and it would cover our planet’s surface to a depth of over five feet.

Titan’s hazy atmosphere – the most Earthlike in our solar system
Based on recent estimates from the Kepler Space Telescope, there are billions of Earthlike planets in our galaxy alone – around one per star, on average. With billions of galaxies in the Universe, we now think that there are more Earthlike planets than grains of sand on all the beaches of Earth. That’s a lot of potential life as we know it, but if we include life in more exotic environments like icy moons, the conditions for life are ten time more common than that. Even in our own solar system, there are a dozen worlds that support liquid water and could, by that definition, be considered habitable. 

Of these, Jupiter’s moon Europa is perhaps the best prospect for life, with a liquid water ocean heated by regular tidal flexing in mighty Jupiter’s gravitational field. Almost entirely isolated from the outside world (there is evidence that liquid water occasionally rises and bursts through the icy surface), Europa’s ocean floor is in direct contact with the bedrock beneath, where there should be thermal vents spewing out energy and nutrients. On Earth, these ocean floor thermal vents are cradles of life, and similar to the primitive ecosystems that nurtured the origin of life itself.

Europa has a lot more water than even our blue planet
Thus arises a question: since the conditions for life are ubiquitous, is life common in our Universe, or are there challenges to the origin that make life a relative rarity? Although intelligent beings may exist elsewhere in our galaxy, they obviously aren’t exceedingly common or else we would have extraterrestrials roaming around our solar system or perhaps a nearby star. Yet, this tells us nothing about simpler life which may indeed be common, possibly even to be found on another world orbiting our Sun. Beyond, there could be billions of worlds covered in microorganisms or even simple plants and animals, just waiting to be found. Either we’re alone or we aren’t: both prospects are equally terrifying. Our curiosity drives us to search for answers, as living beings connected to the Universe.