Book Review: Solar Sails – A Novel Approach to Interplanetary Travel
Written by Mark Mortimer
Great pleasure can be had in sailing across a gentle, blue sea with a fair wind at the back. With little more effort than a slight nudge upon the tiller, you and your craft can travel great distances at a leisurely, enjoyable, relaxing pace. Now, replace wind and water by sail and photon as a trio of authors write in their book "Solar Sails – A Novel Approach to Interplanetary Travel". In it, Giovanni Vulpetti, Les Johnson and Gregory L. Matloff show a very capable and promising method of local and interstellar travel.
Solar sailing uses the push of sunlight against a collector or sail to move a craft. With the absorption and/or reflection of photons, the craft continues to accelerate so that, after making a sun dive, it could travel out of our solar system at velocities in excess of 500 kilometres per second. This idea is so promising that most major national space agencies are looking into sail material and optimal flight paths.
To get you on your way, this book serves as an introduction to the idea of solar sailing. It starts with a review of rocket physics. Then there's a section that discusses the pro's and con's of chemical and nuclear propulsion, as well as some more exotic ones, like Bussard's proton-fusing interstellar ramjet. However, much of the writing serves to inform the reader of the impractical nature of such forms of propulsion. Hence, by contrast, this section capably serves to show the practical nature of solar sails.
Having provided this belief that solar sails are practical and feasible with current technology, the book continues by describing solar sails in more detail. It discusses sail manufacturing, sail craft construction and delivery, and, methods of sailing or tacking. By using common nomenclature, the book easily conveys the necessary scientific elements to both a generalist and a space enthusiast. Some times it gets a bit technical, such as when describing the use of the Jovian magnetic field as an energy source. But, these tend to make the book more valuable than overly complicated.
The book concludes with technical aspects. Here, it provides details aimed to attract the interest of graduate and post-graduate students. And, there's lots to attract, especially as so little space validation has occurred for this technology. Whether unfurling space sails, dealing with desorption, or controlling nanobots, this book provides many challenges and lots of promise for the future but also recognizes a need for a lot of effort to reach maturity. Yet, the book shows, through references to individuals' work and the work of national space agencies, that the concept is real, practicable and potentially very rewarding.
The next time you're floating along on your yacht or dreaming along in your armchair, take your sailing dreams to another level. Giovanni Vulpetti, Les Johnson and Gregory L. Matloff's book "Solar Sails – A Novel Approach to Interplanetary Travel" let you see how a well known and practised human skill can be used well away from the water's surface. From it, we can see how Earth's water can slip far astern while the horizons of different planets fill the view over the bow.
Read more reviews or purchase a copy online from Amazon.com.
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March 12th, 2009 at 12:11 pm
I thought solar sails were considered unpractical. They sure look elegant and fuel efficient.
March 12th, 2009 at 12:34 pm
Riiiight so I had this thought some time ago and was discussing it with some friends, tell me if I'm crazy but based on the idea that a Solar Sail works using Photons, which are emitted pretty much Constantly by Every Star in the Universe, doesn't it hold to bear that Perhaps these same Photons are all pushing against every star in the Universe Too? A force which would essentially originate from all directions and Push in All directions? Maybe having the effect of, you know, pushing the Universe apart at an accelerating rate.
And since we're on the subject anyhow, might all of those Photons which have been emitted since the beginning of time and are now spread throughout the universe in streams of light from their point of origin potentially have some quantifiable mass and maybe explain the whole question of Dark Matter and Dark Energy in one fell swoop? Granted I'm no physicist but it makes sense to me.
I'd love to hear from anyone with feed back. It's among several notions I've been entertaining for some time.
March 12th, 2009 at 12:38 pm
Even though there is still so much to explore in our solar system, I would love to see a probe designed for the sole purpose of reaching the fasted speed that any human made object has achieved and in the process leave the solar system. I wonder if this could be achieved with the combination of solar sails and ion propulsion. The study of the solar wind boundaries could benefit from such a project.
March 12th, 2009 at 1:05 pm
ND: i was thinking exactly same thing, add Chemical engine for the first kick.
Chemical engine + solar sail + ion drive, and let it run towards closest star (other than the sun). See how fast and far can it go…We can open a pool bet when will it overtake Voyager and Pioneer spacecrafts.
of course put tons of equipment on it to do all the science you want.
Who's with me on this?
Joe.TO.
March 12th, 2009 at 1:15 pm
Joe,
the added tons of equipments would mean a lower top speed tho.
I would also like to see a second project to test the Pioneer gravitational anamolies. Basically send at least 2 probes in different directions away from the sun and away from any planets, and with no thrusters and see how far off they are from their projected positions. Not exactly related to the topic of solar sails but that would be an interesting project.
March 12th, 2009 at 2:13 pm
The speed of a light sail mentioned, 5000 km/s is interesting – in that it appears to be close to the threshold of a useful interstellar (or at least a precursor) mission speed. This is the equivalent of 0.016C or 1.6% sol (speed of light); cruising at this speed would allow a craft to cross one light year in about 60 years. A one-way trip to Proxima Centauri (4.2 light years/1.288 parsecs) would take about 255 years.
The Earth orbits the Sun at about 6.28 AU/year; so Solar escape velocity at 1 AU is about 8.88 AU/year. The quoted speed is approximately equal to 1,050 AU/year. The only remaining question(s) then seem to be: how long would a light sail take, with or without chemical/ion drive boosters; to reach 5000 km/s – and when might such a mission be launched?
Even if an interstellar mission is not feasible in the shorter term, missions to the “focal point” gravitational lensing region of about 550 AU become a useful first target – as this area could be reached in six months at this speed; and to the Oort Cloud in less than a year!!!
March 12th, 2009 at 2:20 pm
Totally forgot about the Oort cloud! OC or bust!
March 12th, 2009 at 3:38 pm
I doubt a Solar Sail would be of much use beyond the Solar System, especially in an application that would require it to approach another star since you can't really sail into the wind and the Solar Wind is thought to peter out at the Bow Shock formed by the Sun's Magnetosphere.
March 12th, 2009 at 4:49 pm
Silver Thread: I remember reading that as you reach approach another star, you can actually use that star's light to help you, so you can actually "sail into the wind."
It's too bad that that one Solar Sail that we launched failed (it wasn't even the fault of the actual Solar-Sailing craft!)
March 12th, 2009 at 8:21 pm
If the sail is dismountable, then by furling the sail, under local software control, the achieved momentum (a velocity of 5000km/s sounds exhilarating!) can be retained even when approaching a stronger source of solar/other particles? Also angling the sail could effect a change of course, Water bound yachties will understand the principle readily, perhaps enabling the odd slingshot manouvure? By diving into our sun, skirting the gravity well, we could attain an initial velocity that would only increase as the craft sped away from the sun?
The effect of slowing the craft by unfurling the sail, would be useful as much of spacecraft fuel is in fact designed to be used to deccelerate the craft as increasing velocity is easy, although it can take time. Decceleration can be abrupt though!
Here is an idea that I donate to mankind and to oillsmisery also, that the sail be capable of being augmented by the machine itself, while approaching the sun, by incorporating the protons into a sail framework. How the hydrogen could be formed into a sail escapes me, but perhaps not you? Neutralizing some of these these ions would require a source of electricity, so solar panels would be necessary for this purpose and to power transmissions to earth. By leaving the augmented sail with an overall positive charge, the positive ions might impart extra kick?
March 13th, 2009 at 10:31 am
Dear readers,
thank you very much for your comments and discussions. Yes, ion propulsion and solar sailing may in principle produce some speed very, very high. I studied and presented my first results about such propulsive combination in 1992, at the first World Space Congress held in Washington D.C.
What could surprise is the mathematical fact (already published in Journals) that, using sunlight and solar gravity smartly , there is no need to use (massive) ion propulsion, which entails nuclear power-plants for extra solar missions, in order to go beyond the heliosphere, far, very far to the solar gravitational lens in few years or so. We are studying a new sail technology for transforming such mathematical equations into a reality. We need some years of considerable efforts.
All this does not mean that ion propulsion is useless in general; on the contrary, it may be very effective in plenty of space mission classes, as it is known.
Best regards
Giovanni Vulpetti
March 13th, 2009 at 3:39 pm
A 5,000 km/s capability suggests a viable mission scenario in the post-2020 era for an early interstellar precursor mission. A spacecraft consisting of a multi-stage hybrid propulsion solar sail module – using an Ares V first stage booster; equipped with an RTG-powered laser/ion-engined upper stage and a solar sail 4th/5th stage module.
This configuration could use a chemical-based phase to exit the Earth-moon system for a 2-year cruise to Jupiter – and then dive into the Sun to within say 0.1 AU, taking about 6 months to get there, and then pick up a high speed boost away by solar sail and towards an initial target of the solar focal point (gravitational lensing region at about 550 AU) taking less than a year to get there. Then progressing out to the Oort Cloud at about 1,000 AU.
This would take such a mission about 3 or 4 years to do what the Pioneer/Voyager/New Horizons missions would require about a 100 years to achieve. Depending on its launch year, the earlier craft will have reached 200/300 AU from the Sun by then; even so the new mission would by pass them within 3 to 4 years after launch.