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.

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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.

Interview with Morgan Rehnberg

Morgan is a Director of Scientific Presentation at the Fort Worth Museum of Science and History in Forth Worth, TX. He received his PhD in astrophysics and planetary science from the University of Colorado in 2017. Morgan is mostly known from his work on Saturn and it's rings using data gathered by Cassini spacecraft. He's a frequent guest on Fraser Cain's YouTube series "Weekly Space Hangouts" and a writer for popular series "SciShow Space". Lately Morgan is involved in a project called "Chart Your World" (https://chartyourworld.org). It aims to take the most interesting and important datasets and visualize them in a way that's easy to understand and easy to share.

Mateusz Macias: Hello Morgan, thank you for sharing your time and doing this interview with me.
Morgan Rehnberg: Hi Mateusz, it's great to talk to you!

Mateusz Macias: I'll usually ask my panelists how did theirs adventure with astronomy started. Let's keep up the tradition. How did your fascination with astronomy started and who or what inspired you?
Morgan Rehnberg: Honestly, I never had a particular fascination with astronomy growing up. In fact, when I went to college, my intention was to become a high school chemistry teacher! That quickly turned into physics, but it's really only an accident of having an astronomer as a faculty adviser that turned me onto the field.

Mateusz Macias: We all know you mostly from your work on Saturn and it's rings. Cassini's mission is about to end soon, where do you see yourself when Cassini end it's life plunging into Saturn?
Morgan Rehnberg: Like the rest of the world, I'll be on the edge of my seat, waiting for those last amazing images that Cassini will return. Cassini's Grand Finale, currently underway, promises to bring us some critical information for understanding the rings

Mateusz Macias: What data can Cassini stream back to Earth in it's last days? On what data researchers want to focus on?
Morgan Rehnberg: I don't have any connection to the planning of the Grand Finale, but my understanding is that the spacecraft will return its final images several hours before the expected end and then continuously transmit other forms of data during the plunge into Saturn. From the perspective of a researcher on planetary rings, the Grand Finale is already revealing new information. We learned during Cassini's first trip between the planet and its rings that the region is far more empty than we might have imagined. This is actually good news, because it will allow the spacecraft the freedom to maneuver during upcoming trips

Mateusz Macias: Taking all these years into consideration, what were Cassini's biggest achievements?
Morgan Rehnberg: I think the biggest discoveries made by the mission are with respect to Saturn's moons. Landing the Huygens probe on the surface of Titan was a tremendous achievement. Our overall understanding of Titan has improved dramatically and it must now be considered among the Solar System's most intriguing locations. After all, it's the only place outside of Earth to have liquid on its surface! Combine that with its thick atmosphere, and we can think of Titan in many ways as another terrestrial planet. Of course, the discovery of plumes emanating from Enceladus is another major accomplishment and one that is just as important when looking for places that resemble Earth. Titan may have surface liquid, but methane and ethane are more or less toxic to life as we know it. Enceladus has liquid water, essentially the only thing all life on Earth has in common! From the perspective of planetary rings, the fact that a moon is creating one of the planet's largest rings is also really fascinating

Mateusz Macias: Will we see you working through the data of another NASA mission? What could be the next step for you after Cassini and Saturn?
Morgan Rehnberg: Having recently defended my PhD, I'm excited to be taking on the next stage of my career, but that won't be focused on research. Starting in July, I'll be working as the Director for Scientific Presentation at the Fort Worth Museum of Science and History. One of my long-running interests is in how to use all our amazing modern technology to bring people closer to science and I'm really looking forward to getting to pursue that full-time. Of course, I'd never rule out getting the chance to work on another NASA mission. Maybe when we go to Uranus...

Mateusz Macias: If you had the chance to choose a mission you could be working on, which present or future mission would you pick?
Morgan Rehnberg: It's outside my area of expertise, but I'm really fascinated with the upcoming Lucy mission. This spacecraft will visit a number of Trojan asteroids, a population which shares its orbit with Jupiter. We think Jupiter might have migrated to its present location early in the Solar System's history and, if so, it probably brought the Trojans along for the ride. The Trojans are probably as numerous as the members of the main asteroid belt, so this is really an untaped region for exploration.

Mateusz Macias: If we send another mission to Saturn, what instruments should we have at our disposal? What would you like to research next time Cassini-type spacecraft enters Saturn's orbit?
Morgan Rehnberg: I'm not sure I would send another Cassini-type spacecraft to Saturn. The mission has provided a remarkable overview of the entire system and I think we'd be best off investing in smaller, more targeted missions to explore some of the things Cassini has revealed. People have been kicking around the idea of an airship or a boat for the atmosphere of Titan, for example. That would help us understand surface conditions in a way we'll never be able to from space. A lander in the vicinity of the Enceladus plumes would be able to provide similar context. With respect to the rings, Cassini has revealed that they are far more dynamic on small scales than we'd previously imagined. Now that we understand better where the safe regions of the system are, I'd like to be able to get closer and take pictures that help us see some of the rings' small structures directly.

Mateusz Macias: Let's leave Saturn for now. You're a writer for YouTube's SciShow Space. How did that part of your life started?
Morgan Rehnberg: SciShow is one of the best producers of science content available online today. It's no surprise that more and more people are consuming their videos and that has enabled them to keep expanding what they offer. I had heard that they were looking for some additional writers for SciShow Space and just had to get in touch. I work with them on a freelance basis and it's been quite the education!

Mateusz Macias: You're also an active participant in Weekly Space Hangouts hosted by Fraser Cain. What's the best part in sharing your knowledge with people over the internet?
Morgan Rehnberg: It's great to see how passionate people are about understanding the Universe. When you're deep in a research project, it can be very easy to lose sight of why what you're doing matters. Engaging with nonscientists is always really energizing for me.

Mateusz Macias: Have you ever wondered about writing a book? Sharing fascinating facts about our Solar System comes with ease to you.
Morgan Rehnberg: I'd love to write a book, but that's a big commitment! I also have a lot of ideas that aren't well connected to each other right now. Once I start to fit those into a larger picture, I'll definitely be thinking about whether a book is the right outlet for it all.

Mateusz Macias: When you're not working on Cassini data or sharing your knowledge on social media - what do you do in your spare time?
Morgan Rehnberg: Lately, I've been working on a project called Chart Your World that has really pulled me in. The recent election in the US and other elections around the world have highlighted the need for our societal conversations to include more specific facts. The governments of the world produce a tremendous amount of data, but its rarely very accessible to the average citizen. Chart Your World aims to take the most interesting and important datasets and visualize them in a way that's easy to understand and easy to share. I've got a website up at https://chartyourworld.org and the Twitter account @ChartYourWorld. Now that my dissertation is complete, I'm looking forward to devoting more time to this project.

Mateusz Macias: Great initiative, are there also astronomy related datasets?
Morgan Rehnberg: Nope, this is focused entirely on things here on Earth!

Mateusz Macias: Where could someone meet you for a chat about astronomy and space? Are you giving talks in the near future?
Morgan Rehnberg: I'm looking forward to getting many more opportunities to meet people in my new job at the Fort Worth Museum of Science and History. Now that I'll no longer be a student, I'm also hoping to get out to many more science-themed events around the US!

Mateusz Macias: Any plans of visiting Europe?
Morgan Rehnberg: I've been a few times in recent years, but always for vacation! Hopefully work will take me there even more often...

Mateusz Macias: Morgan thank you again for your time, it's been a blast. Hope to do that again in the future.
Morgan Rehnberg: Thanks for having me and I hope for the same!

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 (http://twitter.com/astronomyfinest).

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.

“The Search for Life in the Universe” by Antonio Paris

Nearly 2,500 years ago the Greek philosopher Metrodorus of Chios challenged his students with an analogy. He stated that, because it was unreasonable that in a large field only one shaft of wheat should grow, why then, in an infinite universe, should there be only one living world? Our understanding of how profligate and diverse life is on Earth and recent discoveries in astronomy point to tantalizing possibilities.

When speculating on the nature of advanced extraterrestrial life and a spacefaring extraterrestrial society, some authors go to great lengths to discuss such life forms’ behavior and how they might be disposed toward us, the lifespan of an advanced technological civilization, and so on. At this stage in our understanding, however, all bets are off. If we were to encounter an advanced spacefaring species, we would be confronted with an intelligence that we have never before encountered, one that may not even be possible for us to understand. We cannot assume that an alien species would be motivated as we are, or would share any universal system of values with us, or perhaps even recognize us. At the moment, our understanding of life is confined to its forms, plentiful and varied though they be, found only on our home planet. Assuming that life has arisen elsewhere in our cosmos, it is almost certain to be very different from anything we currently understand, and it would not have the humanoid structure routinely reported in the UFO community or in science fiction.

Biologists define life by four general processes: growth, reproduction, responsiveness, and metabolism. Scientists are in general agreement that if a collection of organic molecules increases in size, if it makes copies of itself, if it somehow responds to its environment, and if it somehow incorporates elements from outside its structure and converts them in a series of controlled internal chemical reactions to compounds needed to grow, reproduce, or physically respond to changes in its environment, it is alive.

In the early 1960s Frank Drake conducted the first search for radio wave signals from potential extraterrestrial civilizations at the National Radio Astronomy Observatory in Green Bank, West Virginia. This began the international effort in astronomy known today as the Search for Extraterrestrial Intelligence, or SETI. In 1961, when the National Academy of Sciences asked him to chair a meeting on the detection of extraterrestrial intelligence, Drake developed his famous equation designed to estimate the number of advanced technical civilizations in our galaxy. In 1980, Carl Sagan popularized this equation in his television series Cosmos to point out to viewers across the world that our own galaxy might well be teeming with not only life but also other advanced technological civilizations. Professor Drake persuaded astronomers and other interested researchers to think seriously about the possibility of other intelligent life in our galaxy, and Sagan persuaded the common man to think about that same possibility, including its implications for our own existence.

We may be assuming too much in thinking that we would be able to recognize an alien intelligence, civilization, or its artifacts. Without a better understanding of how and where life can arise and of what other forms an alien intelligence or civilization can take, any number concerning the Drake Equation is next to meaningless. However, what Professor Drake’s equation has done, even in the absence of hard data, is to stimulate thought and debate about the various factors necessary to predict the likelihood of extraterrestrial civilizations in our galaxy.

It is arguable that any organism possessing spacefaring technology, as we know it, would have had to develop a sophisticated understanding of physics and be able to comprehend mathematical concepts, thereby recognizing a basic order in the universe’s physics and in our symbology. At the same time, of course, symbols such as letters or numerals are normally arbitrary, bearing little resemblance to what they signify, so it is difficult to say whether an alien civilization could make heads or tails of our messages, and vice versa. Still, Drake and Sagan were optimistically banking on the commonalities that we would share with another species. They knew the differences would be vast but thought it better to begin with the traits that we likely share, such as a similar chemistry involving hydrogen, one of the most common elements in the known universe.

For all our cryptographic abilities, however, we again assume much. We assume, for example, that any intelligent recipients generally think the way we do, that they organize information in more or less the same manner we do, and that they are primarily visual creatures. We are limited by our lack of knowledge of how an intelligence from another world might “think.” We must be careful not to assume that life based on a completely different biology would have anything but the most fundamental chemical elements in common with us.

As we are contemplating extraterrestrial life, one of the more exciting exercises is to imagine what such life might actually look like. If extraterrestrial life is built by DNA, or some equivalent of it, we might hypothesize that such organisms reproduce much as we do. Life evolving on any planet would certainly need to adjust to its gravity, so any sort of alien animal life would have to evolve an anatomy to move through its environment. Such organisms would be very recognizable to us as life forms, but perhaps it is not that simple. British astronomer Martin Rees has posited that there could be organisms and extraterrestrial intelligence in forms we can’t even conceive. We tend to think in terms of “animals” and “plants.” Moreover, the basis of all Earth life appears to be cellular. Whether those cells are eukaryotes, prokaryotes, or archaea, living things on our planet are either single-celled or multicellular organisms. But what if non-Earth life is built of something other than DNA or even an equivalent? We might not recognize it at all. Certainly an intelligence evolved from a profoundly different biology would function very differently than our own. Sagan wrote that extraterrestrial intelligence would be “elegant, complex, internally consistent, and utterly alien.” If we restrict our theorizing to intelligences recognizable to us, however, we could hypothesize that an intelligent extraterrestrial species might have evolved as social life forms. If such a species were also aggressive and highly competitive, as Stephen Hawking recently suggested in an article in the London Sunday Times, we could easily be faced with alien versions of the worst aspects of our human selves. In fact, Hawking cautioned against broadcasting our existence to potential extraterrestrial civilizations, stating that we only have to look at ourselves to see how intelligent life might develop into something we wouldn’t want to encounter. Rather than benevolent extraterrestrials as depicted in much science fiction, he posited that intelligent alien life might come to Earth “in massive ships, having used up all the resources from their home planet. Such advanced aliens would perhaps become nomads, looking to conquer and colonize whatever planets they can reach.” Humanity would almost certainly be helpless in a confrontation with any species advanced enough to locate our planet and travel here.

In all of our theorizing about extraterrestrial intelligence, we may just as easily suppose that, if such a civilization developed technology sufficiently advanced to explore the stars, they must have harnessed that better nature and progressed beyond base instincts. Such a species might therefore not be bent on conquering the Earth or appropriating its resources. It might ignore us altogether, or it might attempt to contact us, perhaps even engage with us. For the moment, until we have irrefutable evidence of intelligent life beyond Earth, it is impossible to know.

Despite the interesting possibilities raised by Drake’s equation and continuing discoveries of new Earth-sized worlds in our galaxy, physicist Enrico Fermi’s question still nags: “Where are they? Where is everybody?” Could humanity be alone in this vast cosmos? For the moment, it seems that we are far distant from any other life forms that we can recognize in our obscure corner of the Milky Way.