Destination: Mars

Mars will become a touristic destination in a matter of 20 years. At what price for a round trip would you consider buying a ticket? What safety concerns would have to be met to sway you over?
Ciro Villa (technologist, application developer, STEM communicator)

First and foremost, whether Mars will become a tourist destination in the next 20 years or not, it's still to be seen and subject to debate. There are still several critical hurdles to be overcome: financial, technical and societal just to name some of the main ones. As of today, these hurdles make just the prospect of humans traveling, let alone landing and settling on the red planet all but trivial and extremely challenging. Initially when human travel to the Red planet will begin, only trained astronauts will venture and embark in the journey that will no doubt be filled with difficulties and perils.

When and if we will finally be able to achieve tourism to Mars, prices will at the beginning undoubtedly be highly prohibitive and most likely out of reach for a large swat of the human population. I personally would most likely not be able to afford the journey in my lifetime. It is indeed hard to place a fair price tags with so many unknowns still in place.

If we let our fantasy go wild, then I would envision that in another 100 to 150-year technology will have advanced to the point to allow for “affordable” and safe commutes with round trips to Mars. I frankly still don’t know what exactly that price tag might or should be.

In terms of safety, it is also almost impossible to pinpoint what would be an acceptable threshold of risk metrics that would make me comfortable enough to embark in the journey with a relative degree of confidence that my trip would not be the last of my life. As mentioned in the beginning, obstacles to be overcome in terms of human planetary travel survivability still abound and only after several iterations, including discoveries, advancement in science and technology and lesson learned, would I believe that a journey to the Red Planet might be safe and enjoyable.

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

I'm probably less adventurous than most people. I really love Earth, and I've barely explored this amazing planet and all it offers. I'd want to know that a trip to and from Mars is relatively safe and much much quicker before I was willing to make that journey. I'd do a few months on Mars to see some of the highlights and then I'd like to come home. I would like to experience lower gravity, but that would be even better on the Moon, which is only a few days away.

Paul Carr (Space Systems engineer at NASA, podcaster, blogger, investigator)

I've little doubt that the first tourist tickets to Mars will only be affordable by the wealthy or those able to obtain corporate sponsorship. The cheaper option is likely to be one way ticket, but still far beyond the means of all but a few of us. An optimistic price for a one way ticket in the early days is probably $5 million USD, but it's probably much more than that until Mars travel is far more efficient than it is now. Perhaps I could raise enough for a one way ticket, which I would have to consider if my health holds up long enough. A few million dollars, for the price of wearing corporate logos on my flight suit, might be possible for me.

I don't expect Mars travel to be as safe as getting on a cruise ship or an airliner for a long time to come. We can probably find efficient ways to address such threats as infectious diseases in a closed space, radiation exposure, or social meltdowns, so that the biggest risks are launch and landing. We shouldn't get into the same mentality we had in the early days of the Space Shuttle, with a delusional notion of how safe it is. After the Challenger tragedy in 1986, there was no shortage of astronaut candidates. Some people are willing to take risks if the reward is there. Many people have died leaping off of cliffs in a wingsuit, or climbing high peaks - not because they don't know what the risks are, but because they accept them and proceed nonetheless. We may never lose as many Mars tourists as the 290 people who have died climbing Everest, but it does seem that some will meet their destiny there. Those who fear the risks should stay on Earth, where they will also die when their time comes.

If I could choose, I'd choose to die on another planet.

Nancy Atkinson (Senior Editor for Universe Today, Host of the NASA Lunar Science Institute podcast & a NASA/JPL Solar System Ambassador)

Ah yes, this is what I jokingly call "The Mars Plan," where getting to Mars is a thing that is always 20 years off into the future, no matter when. Humans on Mars was touted as being 20 years away in the 1970's and it is still 20 years away today. Are we actually any closer now to accomplishing this great feat than we were in the 1970's? I'm not very confident that we are. There are still many technical hurdles to leap, like making the trip shorter than 7 months, being able to land large payloads on Mars, and developing habitats and life support systems that are truly foolproof. If someone dies on the first human mission to Mars, that will be the end of it. Also, this is going to cost a lot of money, and there will have to be a payoff in some fashion, whether it is mining, tourism or an Earth-catastrophe management endeavor.

As a journalist, I'm secretly hoping that someone will pay *me* to go to Mars so I can write about it! Otherwise, I don't think I'll ever have enough cash to do it on my own.

To infinity and beyond!

Elon Musk has sent his cherry Tesla Roadster on a Falcon Heavy maiden flight. If it was up to you, what would you send as a payload on that flight and where would it be going?
Mike Simmons (Founder and CEO of "Astronomers without Borders")

What would I send as a payload? Me! Driving a Tesla roadster would be good but it seems to offer little protection.

Seriously, the payload wouldn't have made any difference on the test flight. No one was going to risk a valuable scientific payload on an unproven rocket, especially when the builder says it has only a 50% chance of success. I think the proof of concept for the Falcon Heavy's ability was quite successful.

At first it seemed more than frivolous to send his car into orbit around the Sun. But after seeing the images sent back from it and looking at the attention it got I really like it. The launch is an incredible feat and this quirky way of doing it was just mind-bending. Something different in an era where rocket launches and satellites are becoming routine.

Nancy Atkinson (Senior Editor for Universe Today, Host of the NASA Lunar Science Institute podcast & a NASA/JPL Solar System Ambassador)

I would have loved for SpaceX to include student experiments or some payload chosen by young people. I think that would have been the most altruistic, educational and scientific choice. But if I understand the story correctly, SpaceX had asked NASA and the US Air Force if they were interested in sending a scientific payload, free of charge on the Falcon Heavy. And while I'm not sure about the timing, but I'm betting there was a delay in a response from NASA and the Air Force, and after the answer was no, that left SpaceX to choose something fairly quickly. There may not have been time to develop something like a competition for student experiments. But the live video feed of the Tesla Roadster in orbit of Earth may have been one of the most exciting, inspirational and just plain cool things that kids have seen lately in regards to space exploration, so perhaps the Tesla was the perfect choice.

Paul Carr (Space Systems engineer at NASA, podcaster, blogger, investigator)

I am amused and disappointed at all the noise over Elon Musk’s choice of a dummy payload - his own car. I thought it was very touching and completely appropriate (full disclosure, I am a Tesla shareholder).

It is impossible to tell payload provider before a demonstration launch that their satellite is not at high risk on an unproven rocket. Throughout the long process leading up to the launch, SpaceX had been managing expectations. They have a history of failing early and learning from it. They felt they had all the known unknowns under control, but in a complex system, it is the unknown unknowns that can easily cause a disaster. I have no doubt that SpaceX approached, or were approached by, a a number of entities about having their payload on the demo flight, but all had to accept the risk. It is easy (and lazy) to say that a scientific payload should have flown, but only in hindsight is this possible, and so the word “should" has to be replaced with “could”. As it is, I think Starman was a master stroke of public relations that no one will forget for a long time. The “Don’t Panic!” sign on the dashboard made it perfect for me. I believe Douglas Adams would have been delighted to see that.

If I had about $20 million sitting around idle, and had been approached by SpaceX, I would have offered an infrared telescope to be positioned at one of the Earth-Moon Lagrange points (probably L1, most of the way to the moon from the Earth) to look for temporary moons. These are small asteroids that are captured into the Earth-Moon system, stay for a few orbits, and then get flung back out into the solar system. At present, we discover them pretty much by luck, if int all. A more systematic survey would provide a more accurate census of these objects, and other Near Earth objects as well. Flying all the way to a Lagrange point before the injection burn might have been a strain on the rocket's batteries, but will put that in the bucket of solvable engineering problems. The relight of the upper stage after a days long cruise would be an even better demo than what they got.

My ultimate goal would be to have a squadron of probes ready to shoot out after the temporary moons, and intercept and rendezvous with them to ascertain their mineralogy and ore-bearing potential at close distance. This would be more elaborate and expensive, but the first baby step of a telescope to detect the moons might be worth risking on a demo mission.

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

If I had the opportunity to select the payload for the Falcon Heavy test flight, I would have to admit that the rocket would not be powerful enough. The rocket would have been loaded with an assortment of trinkets that represented all of humanity, such as music and photos from diverse cultures. Now do not get me wrong - a Telsa Roadster is pretty cool. However, a sport car does not represent humanity in a nutshell, but rather it only represented Elon Musk and a select class of citizens most of us will never hold membership in.

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: https://www.youtube.com/watch?v=4IRWsrW99hY

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 Universetoday.com, 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 2 – Skepticism and pseudoscience

YbdEV55

In our second episode I’m joined by Nicole Gugliucci, Bob Novella and Nancy Atkinson. We talk about science, skepticism and some of the strangest pseudosciences. We give a shout out to some of the good guys in the field of science outreach.

Links:

Nicole Gugliucci (One Astronomer’s Noise)

Bob Novella (Skeptics Guide to the Universe)

Nancy Atkinson (Nancy’s blog)

Credits:

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 info@astronomyfinest.com. If you like our podcast leave us a review on itunes, stitcher or your podcast app. You can also support us on Patreon at patreon.com/astronomyfinest. Music was provided by Kedenna and is used with permission.

2018

It’s this time of year when we make predictions for the upcoming year. What should we look for in the year 2018? What event or mission will be on everyone’s lips next year?
Fraser Cain (publisher at Universetoday.com, co-host of Astronomy Cast)

There are a couple of big missions coming from SpaceX that I think will keep people on their toes. The first, of course is the launch of SpaceX's Falcon Heavy Rocket, which has been delayed for several years now. This will bring serious heavy lift capability to SpaceX, which has only been possible from the traditional launch providers. In addition, SpaceX is expected to launch a couple of space tourists on circumlunar trajectory on board a Dragon capsule This will be the first time humans have gone beyond low Earth orbit since the Apollo era. Of course, SpaceX timelines will likely slip, so it's entirely possible that these predictions will be totally wrong.

In terms of astronomy, I think the result I'm most excited about will be the first pictures from the Event Horizon Telescope, which gathered data back in April 2017. To think that we'll see an image of the region around a black hole is mind boggling.

Of course, the biggest things will be the unexpected. 2017 surprised us, and I'm sure 2018 will surprise us too.

Nancy Atkinson (Senior Editor for Universe Today, Host of the NASA Lunar Science Institute podcast & a NASA/JPL Solar System Ambassador)

Although I’m a big fan of every “branch” of space exploration, I’m especially interested in planetary exploration (and that’s why I wrote a book about it!) There are several big planetary events coming up in 2018 and I’m looking forward to all of them. The InSight seismology probe is scheduled to launch to Mars in May, and land later this year. There are two asteroid sample missions that will arrive at their destinations this year: OSIRIS-REx will reach Bennu in August, and Hayabusa 2 is scheduled to reach Ryugu in July. Also, ESA and JAXA are teaming up to launch BepiColombo to Mercury in October (arriving in 2025). China is expected to launch the Chang'e 4 lander/rover sometime this year to land on the moon’s far side.

Of course, all the current planetary missions will continue to awe and amaze us: Juno is telling us more about Jupiter while sending back incredible images; the two Mars rovers carry on with their journeys across the surface of the Red Planet, Dawn is still orbiting Ceres, and at the end of the year, New Horizons will be approaching its next target, an intruging Kuiper Belt Object. So, there will be no shortage of exciting planetary science news to cover in 2018!

Seth Shostak (Senior Astronomer and Director of the Center for SETI Research at SETI Institute)

Discovery of a new, big planet in the outer solar system.

Paul Carr (Space Systems engineer at NASA, podcaster, blogger, investigator)

The first thing should be the launch of the Falcon Heavy. We don’t yet know how important a launch vehicle the Heavy will be, but stay tuned for a wonderful spectacle as multiple boosters return to the launch site at once.

The planned launch of TESS is probably the biggest item on my list. It will take a few months to settle into the science, but towards the end of 2018 TESS should start delivering a much better census of planets, especially Earths and Super Earths that are relatively near to us compared to Kepler’s discoveries. We might even find some Earth-like planets quite close by. Along with follow-up ground observations, this should push us truly into the golden age of exoplanet discoveries.

Another big event at about the same time as the TESS launch is the Gaia DR2 data release. I am especially hoping for much smaller error bars on the distance to Boyajian’s Star, which would help to constrain theories about what causes the slow dimming ad brightening episodes we observe.

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.


Links:

Astronomers Without Borders

Andrew Rader’s website

Credits:

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 info@astronomyfinest.com. If you like our podcast leave us a review on itunes, stitcher or your podcast app. You can also support us on Patreon at patreon.com/astronomyfinest. Music was provided by Kedenna and is used with permission.

Is It Time To Go Back to Uranus and Neptune? Revisiting Ice Giants of the Solar System

We’ve only seen Uranus and Neptune one time up close. There are now some mission ideas in the works that might take us back.

Continue reading “Is It Time To Go Back to Uranus and Neptune? Revisiting Ice Giants of the Solar System”

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 mateusz.macias@astronomyfinest.com.

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 Universetoday.com, 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 (https://en.wikipedia.org/wiki/List_of_spacecraft_with_electric_propulsion). 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.