A Solar Sail Manifesto

by Paul Gilster on April 30, 2009

I was startled to see the Breakthrough Propulsion Physics project make the pages of The Atlantic in its current issue. Novelist Thomas Mallon, in an essay largely devoted to solar sailing and The Planetary Society’s efforts in that direction, gives vent to some of the frustration, if not exasperation, many of us feel as we see basic research losing out to short-term missions whose purpose is by no means clear. “American politicians now mostly avoid the old conditional trope ‘If we can put a man on the moon’ — because we can’t, not anymore,” writes Mallon, who goes on to lament the passage of the BPP project and, five years later, NASA’s Institute for Advanced Concepts.

Questioning Why We Explore

In Mallon’s view, the sense of exploration is itself under attack:

Even the most spectacular unmanned successes of the American space program — from the Voyager probes of the ’70s to the Galileo and Cassini missions of the ’90s — seem to belong to a fading worldview. A desire to explore, even by mechanical proxy, is now a self-indulgence to be resisted, since the end result would only be the imperial spreading of that pollutant known as humankind. In the new view, people have made such a mess of things here that we have no right to any more of the universe, and certainly not to a “backup planet,” which some space enthusiasts have suggested as the ultimate hedge against environmental catastrophe on Earth.

This would once have struck me as a Jeremiah-like screed, but that was before I began routinely writing of these matters and hearing comments to much the same effect. The worst example of this misanthropic worldview I’ve encountered occurred at a dinner party where the subject of space exploration came up. I was defending the idea of expanding into the Solar System as a necessity in terms of acquiring the tools of asteroid deflection, at which point my host said that an incoming asteroid would do the universe a favor if it destroyed our planet, and that we shouldn’t try to stop it.

Statements like that are easy to make and seem to confer a kind of cynical sophistication on those who speak them, but of course the response is this: If you choose to commit suicide, that’s your decision, but do you really think you have the right to make it for your children and grandchildren? The answer being no, then developing at least enough smarts about space travel to reach and change the trajectory of incoming objects should be a high priority for our species.

solar_sail_five

Hope for a Second Cosmos

Mallon’s point in The Atlantic, however, is not to explore our modern fatalism but to showcase solar sailing, and in particular, the experiment called Cosmos 1, a solar sail whose Volna booster failed to deliver it to orbit. A Cosmos 2 is in the cards, or so believes Louis Friedman, whose continuing labors for The Planetary Society keep him on the plane to Moscow as he tries to keep his Russian/American team intact. It’s reassuring to read that any Cosmos 2 attempt will not fly on a Volna.

Image: What might have been — Cosmos 1 in space. Credit: Rick Sternbach/The Planetary Society.

And how invigorating to see that the fundamentals of solar sailing, which many of us believe will be the workhorse of our early space infrastructure, are laid out for an audience not generally given to these matters. Thus Mallon’s conversation in Pasadena with Friedman, Bud Schurmeier (retired Voyager project manager) and astronautics veteran Viktor Kerzhanovich:

“Light has energy,” said Friedman. “That you can’t argue with.”

“More important,” said Kerzhanovich, “it has momentum.”

“Therefore it has a force,” added Friedman. “You’re using the energy of light, and the force derived thereof, to transfer momentum of light energy to your vehicle, in order to propel the spacecraft. Basically your spacecraft, your solar sail, looks like a sail, but it really is a mirror. And so it’s reflecting the light, and that reflection is where the momentum transfer occurs.” If the mirror were fixed to a wall, there would be no transfer. But in free space, with no gravity and no air pressure? You’re off to the cosmic races.

“It’s not the solar wind,” Friedman reminded me.

“Things got named wrong,” said Schurmeier. However pretty it sounds, “sailing” is really a metaphor. There is such a thing as solar wind, but as Friedman explained, “Solar wind is electrons and protons that come from the sun, and they have mass, but they go very much slower than light.”

It’s photons, not protons, that we’re talking about?

“Right,” said Friedman. “Photons have no mass, they’re all energy. You do get a force from the solar wind, but it’s about a thousand times less than the force you get from this reflection. You turn your mirror in different directions, you can point the force in any direction you want!”

Getting a Sail into Space

solar_sail_six

And so on. It’s been ninety years since Friedrich Tsander and Konstantin Tsiolkovsky wrote about practical solar sailing and high time we got a sail into Earth orbit to test what can and cannot be done with sunlight. NASA has cut solar sail funding just at the point when we were closing on having the technology operational, as least for test purposes, and the European Space Agency is likewise turning its attentions elsewhere. The Marshall Space Flight Center team has a second NanoSail-D ready for deployment, but who will launch it, who will pay, and when will the event occur? Best to keep The Planetary Society’s efforts in full gear, because someone has to do this.

But in matters like these, everything depends upon funding, and at the moment the money is tight, despite the efforts of Ann Druyan at Cosmos Studios, who is devoting as much personal energy into Cosmos 2 as she did with Cosmos 1. Mallon calls Cosmos 2 “a Hail Mary pass, an audacious leap,” but in reality it’s a simple first step, and a tentative one at that, in pushing solar sail technology to a higher level of readiness. The fact that it has to be done by private initiative instead of government, for the price (as Druyan notes) of “a nice New York apartment,” could actually become its salvation, but only if the right philanthropist decides to dig deep into his pockets.

{ 23 comments }

dad2059 April 30, 2009 at 10:55

Statements like that are easy to make and seem to confer a kind of cynical sophistication on those who speak them, but of course the response is this: If you choose to commit suicide, that’s your decision, but do you really think you have the right to make it for your children and grandchildren?

Yes! Can I get an “Amen!”

Sorry, but I get that a lot too and the answer I get usually is, “well, we’re just saving them from themselves” or “I guess they’ll have nothing to worry about.”

Some of them are good friends. Unfortunately they’re anthropic self-haters!

Like Ann Druyan said, it’s going to have to take a philanthropist/entrepreneur with deep pockets (Branson, Beeson and Musk come to mind) to get these forward thinking and necessary projects off the ground.

Heinlein would agree.

Athena Andreadis April 30, 2009 at 12:31

This sophisticated cynicism, which became de rigueur with cyberpunk, invariably arises during times of cultural and economic contraction. The US imperium is either coming to its end or will survive in much reduced form, hence the angst. At the same time, the finiteness of resources on earth has come into sharp focus. So we can either give up technology and suffer the consequences — as advocated by the (execrable, in my opinion) Battlestar Galactica reboot — or take responsibility for our actions and try to forge a collective solution that will attempt to save the planet and its species, including us. This must needs include severe curbs on human population growth, with all its social implications.

ad April 30, 2009 at 13:15

“If you choose to commit suicide”, why haven’t you done so already?

ljk April 30, 2009 at 13:56

The new CGI film titled Battle for Terra has a plot about the future
of the surviving members of the human race, after trashing Earth and
its neighboring worlds in a combination of neglect, greed, and wars,
going out into the galaxy in search of a new planet to settle.

They find a suitable place occupied by nice, peaceful beings who
have learned to live with nature. Naturally the humans are far more
interested in moving in than worrying about the property rights of
the natives.

http://www.battleforterra.com/

Once again Hollywood leads the way in this either-or attitude about
our existence and our relationship with nature: Either we are
murderous conquestors of space or we become treehuggers who
throw away all our technology. Both alone will destroy us and
others, but if we can find a balance, then it may make for less
exciting film plots but we will survive and not at the expense of
everything else.

Paul, it is too bad your dinner host did not realize just how big the
Cosmos is and how small we are to it. We may wreck ourselves and
Earth if we are not careful, but that will not even register to the rest
of the galaxy. An odd attitude to take by those who claim to be so
concerned about the preservation of life, as if humanity is somehow
excluded from this protection.

And regarding solar sails, why are only private groups working on
this concept? How expensive and difficult is it for a space agency
to make their own?

Marcel F. Williams April 30, 2009 at 13:57

Lightsails are the key to human expansion into the solar system and the key to the commercialization and industrialization of the solar system, IMO. Unless there is some breakthrough in reliable magnetic or electrostatic shielding, at least several hundred tonnes of mass shielding from galactic radiation are going to be required for humans to travel to Mars or to other planets in the solar system. Extraterrestrially manufactured lightsails appear to be the only economically reasonable transport system potentially capable of transporting hundreds or thousands of tonnes of mass– relatively rapidly– through the solar system.

http://newpapyrusmagazine.blogspot.com/2008/01/space-frontier.html

ljk April 30, 2009 at 14:26

Perhaps this will one day be the ultimate goal of the solar sail concept:

http://eg.orionsarm.com/xcms.php?r=oaeg-view-article&egart_uid=49f85ad889279

Administrator April 30, 2009 at 14:55

ljk writes:

And regarding solar sails, why are only private groups working on this concept? How expensive and difficult is it for a space agency to make their own?

Valid question, especially since NanoSail-D is an on-the-cheap sail that’s already built and flyable! So much of the necessary background work has been done on development that it seems a complete waste to let the talented folks at MSFC and JPL move on to other things, but it’s the way bureaucracies work.

James M. Essig April 30, 2009 at 15:27

Hi Folks;

I find the idea of solar sailing especially whimsical being that is is reminescent of the Glory Days of cross Atlantic sailing that occured in the 15 th century through the 18 th century.

One wonders to what extremes can we take the process of sailing among the stars. Sailing using super refractive and reflective materials in dive and fry manuevers around Blue Hyper Giant stars I have calculated can in simplified models neglecting drag by stellar wind enable us to achieve atleast 96.8 percent the speed of light. Using QUASARs can enable us to reach atleast 99.8 percent the speed of light; all without the need for concentrating the light.

But even the use of QUAZARs has its limits when one considers the R EXP 2 fall off of point source spherically radiating EM emmissions.

I like the idea of using very large area sheets made of superconducting nanowires in a weave pattern that is 99.9999 percent empty space such as might exist using some sort of carbon nanotube or metallic hydrogen wires that are 1 nanometer in diameter that are seperated by 2 millimeters to produce a CMBR reflective net. The trick is to obtain a material the reflects CMBR incident on one side only and possibly optionally absorbtive on the other side and convertable to electrical current for purposes of powering an electrical propulsion system.

For high gamma factors, the CMBR photons incident in the path of the incomming craft could largely be made to: pass between the holes in the net, pass through nearly perfectly transmissive fibers, or be collected and absorbed by super efficient Photovolataic fibers and converted to electrical energy to drive electrical propulsion systems. As the craft gradually approached C, the spacing between the wires could be increased so that the mass specific area of the net as a backside Doppler Redshifted CMBR reflector could be increased.

Note that such materials may sound far out, but metamaterials that have a negative index of refraction for microwave frequencies, and I believe visible light bands have already been demonstrated within the laboratory. Who knows what sort of novel electromagnetic materials might be developed. Check out Duke University’s electromagnetic materials research for more information. They are doing some cool stuff, some of which is bound to be relavent to refined prospects for solar and stellar sailing.

With all of the available ambient EM energy within the planetary, interstellar, and intergalactic environment that we know how to harness with known physical laws and state of the art materials or materials on the drawing boards, we should look carefully as a civilization emerging from our cradle on the prospects of utilizing this real ambient and ever present energy source to sail among the stars.

bigdan201 April 30, 2009 at 16:54

lol, nothing worse than pseudo-intellectual nonsense and attempts at ironic cynicism spouted by those who want to be more high-brow and deeper than you. i wonder if he reads Hemingway and admires modern art.

I digress.

but yea, ive seen that sort of fatalistic self-hate from many others, often stated casually from people who id agree with on other points. It probably does have to do with an angst from our point of history. It is true that we dont have the right to wipe out all future generations too.. its also true that space colonization could help earths environment.. a good argument against those with environment-centric morality.
were certainly not going to help or hurt the universe much. the universe is serious business. the cosmos are so great and vast that it would be difficult for even an advanced civilization to put a dent in them. If we somehow managed to blow up the whole milkyway galaxy and leave a hypergiant black hole behind (hopefully we wont) even that wouldnt affect the universe too much. and even a kardashev 3 civilization which harnesses galaxies would be limited in scope.
overall, were not gonna damage the universe, but we can damage the earths environment, so the best solution from thier own enviro-centric point of view is to colonize space. (keep in mind that collective suicide, whether through an asteroid or nukes, would destroy the earths environment as well).

a couple other points – although humans have had a very violent history, it does speak well of us that weve had nukes for decades and havent destroyed ourselves.
also, ETI will also be evolved from predators and thus have at least some natural aggression. i can elaborate on this if anyones interested.

….

And solar sails seem like a great idea. but nonsense like the iraq war and more recently the financial meltdown will inevitably cut funding to worthy projects.

James M. Essig April 30, 2009 at 22:04

Hi Folks;

Regarding solar, stellar, and CMBR sails, what can be done at one location can be done at multiple locations.

One can imagine a stellar sail that has a flight path that takes it from star to star in repeated dive and fry manuevers wherein the stellar sail picks up significant incremental kinetic energy as it passes from star to star.

The craft could use gravity assists, powered or not, to alter its course perhaps in conjunction with a stellar cycler type of electrodynamic flight path curving mechanism.. Karl Schroeder discusses his Stellar Cycler ideas at http://www.kschroeder.com/my-books/permanence/interstellar-cyclers. Basically, his idea anticipates using the ambient interstellar magnetic fields to interact with a charged member attached to a space craft such as a charged tow line to induce a circular motion or cyclical flight path of an interstellar space craft via the Lorentz Force. I can imagine that such a turning force coupled with gravitational assists can provide a space craft with the ability to reach high gamma factors yet remain within the Milky Way while the gamma factor of the space craft reached very high values as the space craft did multiple loops (or as many as required) in order to be launched on an epic journey of truely cosmic distance proportions.

It is interesting to speculate about harnessing the zero point field energies and the like, and I hope we are indeed able to do such, but it
is of my strongest opinion that interstellar travel at velocities below C but ever closer to C can enable mankind to colonize the obervable universe and beyond, even much further beyond.

With the negative refraction index metamaterials I mentioned above, in theory, stellar sails and even CMBR sails can be manufactured that are ironically pulled forward by the incomming incident light rather than pushed by the light. Note that the theoretical ramifications and theoretical applications of EM negative refraction index materials are still being evaluated, but as of yet no commercial applications have arisen out of such metamaterials research.

Although harnessing the ambient interstellar and intergalactic ambient real energy fields for manned interstellar travel will challenge our scientific and technical abilities as a civilization like nothing before has, I am convinced that the laws of known physics permit us to do such.

The engineering challenges will be enormous, the construction efforts herculian, and the financial resources that will be needed to undertake such a concerted effort if done in our life times will be extreme, but such a project started within the first half of the 21st Century, perhaps even with mission launch sometime during the next 50 years is doable, and nothing like the possibility of developing such a profound technology and precursor missions designed to liberate mankind from the cradle of Earth, with the possibility of meeting any ETI civilizations on our own terms, could so unite the human race under a common rallying call. Interstellar travel rather than being a waste of time has the power to unite the human race as nothing has done before.

Our civilization is a lonely civilization and to reach out and meet any ETI brothers and sisters can only be, in a long run, a profoundly spiritual quest that strikes at the Heart and Soul of anyone who has viewed the vaste expanse of the Milky Way in a dark country location at night.

The challenges will be daunting at times, but we humans can rise to the occasion and I feel that to do such is in our destiny. With such a united and concerted effort, we can build a civilization of love and lasting peace, and with peace all things are possible.

With that being said, any discontinued financial backing of solar sail technologies and precursor missions should be immeadiately reinstated. The financial stakes may be high, but the long term opportuinties afforded such are as limitless as the night sky.

Adam May 1, 2009 at 1:59

I think it would be a sad and sorry thing for such an attitude to proliferate just as we begin to discover the true frequency of Earth-like worlds. If the Galaxy is bare, then misanthropy is misplaced – ethically we’d be facing a challenge, if not a call, to spread Life across the empty wastes.

As for solar-sails, perhaps NASA dislikes them because they’re too ‘easy’ and don’t have any obvious technological pay-off. But there are so many missions that sails, acting as statites and the like, can perform and rockets just can’t. Perhaps NASA lacks imagination or discourages it. Or maybe the Sun and the long-term behaviour of thin-films in space are too big an unknown to attach to a science mission – NASA is a failure averse organisation after all. At least failure they can plan against, not the failure that slips under their oversight.

ethanol May 3, 2009 at 15:10

With respect to the fashionably cynical crowd, my argument is to put your money where your mouth is, though I hate to advocate suicide, let alone genocide.

NASA hasn’t proved entirely resistant to testing advanced propulsion methods. Deep space one, which was nominally to a mission to study asteroids was really more of a test bed for ion drives. I wonder if a mission could be thrown together for using solar sails to do a venus-mercury scientific mission, or something similar that would be hard to achieve using conventional propulsion (of course messenger is doing it with ion drives but its not exactly the simplest or quickest approach)

Administrator May 3, 2009 at 18:09

ethanol, absolutely. But the problem is that the solar sail development, which within NASA got us close to in-space testing capability, has ground to a halt because of lack of funding. A solar sail mission within the Solar System like the one you propose certainly makes sense, though only after we get to a completely operational sail. And right now that first step is stalled, both in ESA and NASA.

Ronald May 4, 2009 at 4:39

I fully agree with Adam: we live in a fascinating and highly promising age, not a time for misanthropy at all. On the eve of discovery of possibly hosts of terrestrial planets. And with regard to those there are only two possibilities: either there is biological life there already, or we face the challenge and calling to bring it there.

Unfortunately, I notice the same misanthropy and cynicism all around, the notion, often even pseudo-religiously or spiritually inspired, that we are fundamentally evil and deserve, even need, to be punished to death, either by a higher being or by Nature, for all we humans can ultimately achieve is spreading death and destruction.

How wrong this view! The mere fact that there are almost 7 billion of us, most of which can expect to live to some 80 years and counting, proves that with all out shortcomings, we deeply desire life, not death and destruction.

We are rather like growing-up children and of course we do make mistakes in our still young and continuous learning process. I would rather compare our role on earth and in the galaxy to gardeners spreading life and in doing so sometimes accidentally disperse a weed as well.

I cannot help but make a comparison with a small but highly interesting natural wetland area here in the Netherlands, the Oostvaardersplassen, which was ‘accidentally’ created when a part of the land that was claimed from the sea by the Dutch in the ’50s, was left alone simply because it wasn’t considered economically feasible to develop for agriculture (too swampy). It is only some 60 km2 (24 mi2 or 15,000 acres), but has become one of the most important bird areas in Europe. Humans originally disseminated a few species, nature took its own course and did the rest.

With regard to the required philanthropist, I agree with dad2059: “it’s going to have to take a philanthropist/entrepreneur with deep pockets (Branson, Beeson and Musk come to mind) to get these forward thinking and necessary projects off the ground”. Yes, a visionary philanthropist, maybe with a touch of (very human) vanity which often leads to the desire to leave something lasting behind. Maybe Gates, Buffett as well?

However, I do think that the visionary/philanthropist funding should foremost be directed toward the discovery of earth analogs, rather than propulsion. First things first: I believe that such a discovery might rekindle public enthousiasm and support for space exploration and the rest would follow.

philw1776 May 4, 2009 at 13:24

Following up on the thoughts about wealthy space sponsors, cynicism about humanity and the possibly positive resurgence of thought were Earth analogs to be fount, were I Bill Gates I’d fund the basic TPF/Darwin mission planet search & spectrograph idea. What a way to be remembered forever, discovering and naming the nearby Earth analogs, assuming of course that there are any.

Ronald May 5, 2009 at 6:04

@philw1776: “were I Bill Gates I’d fund the basic TPF/Darwin mission planet search & spectrograph idea”. As long as we don’t have to call such a discovered earth analog something like Gatesia, Buffettia, let alone Window or New Berkshire ;-)

Exactly what I had in mind as well! And something ground-based like the European Extremely Large Telescope (ELT).

ljk May 6, 2009 at 10:17

We “commoners” tend to forget one important thing about the very
rich: They did not get that way by being overly generous without
expecting something to their benefit in return, if they are generous
at all.

We may keep getting lucky with a few rich individuals who want to
immortalize themselves through some grand space activity, but I for
one am wary of being dependent on the whims of one powerful
individual who could change their mind tomorrow and pull all
funding. Or they could divert a project in a direction that might
please them but go against what everyone else wants.

I hope we can make these kinds of space plans a group effort, where
everyone gets to play a role and have a part in it at least in comparison
to their abilities and resources. One person or one company controlling
it all concerns me on many levels.

ljk July 15, 2009 at 12:02

‘Repulsive’ Side To Light Force Could Control Nanodevices

ScienceDaily (July 13, 2009) — A team of Yale University researchers has discovered a “repulsive” light force that can be used to control components on silicon microchips, meaning future nanodevices could be controlled by light rather than electricity.

The team previously discovered an “attractive” force of light and showed how it could be manipulated to move components in semiconducting micro- and nano-electrical systems—tiny mechanical switches on a chip. The scientists have now uncovered a complementary repulsive force.

Researchers had theorized the existence of both the attractive and repulsive forces since 2005, but the latter had remained unproven until now. The team, led by Hong Tang, assistant professor at Yale’s School of Engineering & Applied Science, reports its findings in the July 13 edition of Nature Photonics’s advanced online publication.

“This completes the picture,” Tang said. “We’ve shown that this is indeed a bipolar light force with both an attractive and repulsive component.”

The attractive and repulsive light forces Tang’s team discovered are separate from the force created by light’s radiation pressure, which pushes against an object as light shines on it. Instead, they push out or pull in sideways from the direction the light travels.

Full article here:

http://www.sciencedaily.com/releases/2009/07/090713131556.htm

ljk August 18, 2009 at 11:05

Evidence for a photon mass

Authors: Burra G.Sidharth

(Submitted on 15 Aug 2009)

Abstract: The author’s work over the past years has indicated that the photon has a small mass $\sim 10^{-33}eV$. Recent observations from three different viewpoints — the time lag in cosmic gamma rays with different frequencies, the observation of the spectra of blazars and an analysis of the CMB power supression from the WMAP data — all vindicate this conclusion and remarkably, the same value.

Comments: 8 pages tex

Subjects: General Physics (physics.gen-ph)

Report number: IIAMIS-TR 090801

Cite as: arXiv:0908.2170v1 [physics.gen-ph]

Submission history

From: Burra Sidharth Gautam [view email]

[v1] Sat, 15 Aug 2009 09:55:20 GMT (6kb)

http://arxiv.org/abs/0908.2170

ljk August 18, 2009 at 11:08

Deviations from Keplerian Orbits for Solar Sails

Authors: Roman Ya. Kezerashvili, Justin F. Vazquez-Poritz

(Submitted on 20 Jul 2009)

Abstract: It is shown that the curvature of spacetime, a possible net electric charge on the sun, a small positive cosmological constant and the oblateness of the sun, in conjunction with solar radiation pressure (SPR), affect the bound orbital motion of solar sails and lead to deviations from Kepler’s third law for heliocentric and non-Keplerian orbits.

With regards to the Lense-Thirring effect, the SRP increases the amount of precession per orbit for polar orbits. Non-Keplerian polar orbits exhibit an analog of the Lense-Thirring effect in which the orbital plane precesses around the sun.

Comments: 6 pages, 2 figures. Proceedings of the Sixth IAA Symposium on Realistic Near-Term Advanced Scientific Space Missions. Missions to the Outer Solar System and Beyond, pp. 37- 42, Aosta, Italy, 6-9 July, 2009

Subjects: General Relativity and Quantum Cosmology (gr-qc); Space Physics (physics.space-ph)

Cite as: arXiv:0907.3311v1 [gr-qc]

Submission history

From: Roman Kezerashvili [view email]

[v1] Mon, 20 Jul 2009 01:28:31 GMT (84kb)

http://arxiv.org/abs/0907.3311

ljk August 18, 2009 at 11:09

Escape Trajectories of Solar Sails and General Relativity

Authors: Roman Ya. Kezerashvili, Justin F. Vazquez-Poritz

(Submitted on 20 Jul 2009)

Abstract: General relativity can have a significant impact on the long-range escape trajectories of solar sails deployed near the sun. Spacetime curvature in the vicinity of the sun can cause a solar sail traveling from 0.01 AU to 2550 AU to be deflected by as much as one million kilometers, and should therefore be taken into account at the beginning of the mission.

There are a number of smaller general relativistic effects, such as frame dragging due to the slow rotation of the sun which can cause a deflection of more than one thousand kilometers.

Comments: 6 pages, 3 figures. Proceedings of the Sixth IAA Symposium on Realistic Near-Term Advanced Scientific Space Missions. Missions to the Outer Solar System and Beyond, pp. 67-72, Aosta, Italy, 6-9 July, 2009

Subjects: General Relativity and Quantum Cosmology (gr-qc); Space Physics
(physics.space-ph)

Cite as: arXiv:0907.3336v1 [gr-qc]

Submission history

From: Roman Kezerashvili [view email]

[v1] Mon, 20 Jul 2009 02:37:38 GMT (204kb)

http://arxiv.org/abs/0907.3336

ljk August 18, 2009 at 11:11

Bound Orbits of Solar Sails and General Relativity

Authors: Roman Ya. Kezerashvili, Justin F. Vazquez-Poritz

(Submitted on 18 Mar 2009 (v1), last revised 25 Mar 2009 (this version, v2))

Abstract: We study how the curvature of spacetime, in conjunction with solar radiation pressure (SRP), affects the bound orbital motion of solar sails. While neither the curvature of spacetime nor the SRP alter the form of Kepler’s third law by themselves, their simultaneous effects lead to deviations from this law.

We also study deviations from Keplerian motion due to frame dragging, the gravitational multipole moments of the sun, a possible net electric charge on the sun, and a positive cosmological constant. The presence of the SRP tends to increase these deviations by several orders of magnitude, possibly rendering some of them detectable. As for non-circular bound orbits, the SRP dampens the rate at which the perihelion is shifted due to curved spacetime, while the perihelion shift due to the oblateness of the sun is increased.

With regards to the Lense-Thirring effect, the SRP increases the angle of precession of polar orbits during one orbital period, although the precession frequency is not actually altered. We also consider non-Keplerian orbits, which lie outside of the plane of the sun.

In particular, we investigate how the pitch angle of the solar sail is affected by the partial absorption of light by the sail, general relativistic effects, and the oblateness of the sun. Non-Keplerian orbits exhibit an analog of the Lense-Thirring effect, in that the orbital plane precesses around the sun.

A near-solar mission for observations of these effects could provide an interesting confirmation of these phenomena.

Comments: 30 pages, 5 figures, minor typos corrected

Subjects: General Relativity and Quantum Cosmology (gr-qc); Space Physics (physics.space-ph)

Cite as: arXiv:0903.3212v2 [gr-qc]

Submission history

From: Justin F. Vazquez-Poritz [view email]

[v1] Wed, 18 Mar 2009 17:56:18 GMT (204kb)

[v2] Wed, 25 Mar 2009 23:54:25 GMT (257kb)

http://arxiv.org/abs/0903.3212

ljk August 18, 2009 at 11:12

Solar Radiation Pressure and Deviations from Keplerian Orbits

Authors: Roman Ya. Kezerashvili, Justin F. Vazquez-Poritz

(Submitted on 12 Jan 2009 (v1), last revised 15 Apr 2009 (this version, v2))

Abstract: Newtonian gravity and general relativity give exactly the same expression for the period of an object in circular orbit around a static central mass. However, when the effects of the curvature of spacetime and solar radiation pressure are considered simultaneously for a solar sail propelled satellite, there is a deviation from Kepler’s third law.

It is shown that solar radiation pressure affects the period of this satellite in two ways: by effectively decreasing the solar mass, thereby increasing the period, and by enhancing the effects of other phenomena, rendering some of them detectable.

In particular, we consider deviations from Keplerian orbits due to spacetime curvature, frame dragging from the rotation of the sun, the oblateness of the sun, a possible net electric charge of the sun, and a very small positive cosmological constant.

Comments: 4 pages, minor typo corrected, additional comments

Subjects: General Relativity and Quantum Cosmology (gr-qc); Space Physics (physics.space-ph)

Journal reference: Physics Letters B 675 (2009) pp. 18-21

Cite as: arXiv:0901.1606v2 [gr-qc]

Submission history

From: Roman Kezerashvili [view email]

[v1] Mon, 12 Jan 2009 16:25:02 GMT (8kb)

[v2] Wed, 15 Apr 2009 19:24:38 GMT (8kb)

http://arxiv.org/abs/0901.1606

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