Our choice of orbits can create scientifically useful space missions that can be operated at lower cost than their more conventional counterparts. How this has been done and the kind of missions it could enable in the future is the subject of James Jason Wentworth’s essay. An amateur astronomer and interstellar travel enthusiast, Wentworth worked at the Miami Space Transit Planetarium and volunteered at the Weintraub Observatory atop the adjacent Miami Museum of Science. Now making his home in Fairbanks (AK), he was the historian for the Poker Flat Research Range sounding rocket launch facility. His space history and advocacy articles have appeared in Quest: The History of Spaceflight magazine and Space News.
by J. Jason Wentworth
In the 1990s, then NASA Administrator Daniel S. Goldin introduced the “Better, Faster, Cheaper” paradigm for space missions. While NASA’s subsequent experiences led many engineers to modify that to “Better, Faster, Cheaper–choose two,” the goal of low cost has remained a primary goal for space mission planners. One way to reduce the cost of a mission is to select a trajectory that requires the least possible change of velocity (called Delta-V by engineers and orbital dynamicists) to achieve the mission’s objectives. This requires less propellant aboard the spacecraft, which results in a smaller and lighter spacecraft, which in turn can usually be lofted by a smaller and less expensive launch vehicle. (Very high-energy missions such as New Horizons are exceptions. In such cases, launching the smallest possible spacecraft merely makes such missions possible within a practical flight duration–even when using the most powerful launch vehicles available–because the velocities required for even the lowest-energy trajectories are so high.)
Another factor that affects the spacecraft’s required amount of onboard propellant is the stability of the mission orbit. If frequent orbital adjustments are necessary for any reason, a larger propellant reserve will be required, which will bump up the probe’s size and mass. The type of spacecraft stabilization system that is used also has an influence on the propellant reserve. A three-axis stabilized probe in orbit around the Moon, the Sun, another planet, or any other body will require more thruster firings (to point its sensors and imaging system at its target body, and to aim its high-gain antenna at Earth) than will a spin-stabilized spacecraft, so the latter can operate for many years using very little propellant for attitude control.
The spin-stabilized Pioneer spacecraft all exhibited this characteristic of very long life. Perhaps the most impressive of the series (besides the Sun-orbiting Pioneer 6 – 9 interplanetary probes, which lasted for multiple decades; two of them may still be functioning) was the Pioneer Venus Orbiter, which returned images of and data on the planet (and Comet Halley) for nearly 14 years, in the hostile thermal and solar radiation environment around Venus. [1] In March of 1986 Pioneer 7 also flew within 12.3 million kilometers (7.6 million miles) of Halley’s Comet and monitored the interaction between the cometary hydrogen tail and the solar wind. It discovered He+ plasma produced by charge exchange of solar wind He++ with neutral cometary material. [2]
Image: Orbit attitude of Pioneer Venus 1 between 1978 – 1980 and 1992. Credit: NASA/Ames.
Since the space age began, other trajectories besides the classical Hohmann transfer ellipse have been devised to get satellites and space probes to their destination orbits or worlds. These are used to minimize the necessary Delta-V, or to optimize planet arrival times, or both. Some geosynchronous satellites are now first injected into “super-synchronous” transfer orbits from their initial low-altitude parking orbits, from which they are later maneuvered downward into their 24-hour operational orbits. The Pioneer Venus Orbiter traveled along a similar path to Venus; it was boosted from its parking orbit around the Earth into a solar orbit that initially passed outside the Earth’s orbit about the Sun before curving inward to intercept Venus in its orbit.
Other unusual types of orbits exist, some of which were discovered when asteroids were found to be moving in them, and they are also useful for low-Delta-V (and thus lower cost) space missions. The best-known ones are halo orbits and the tadpole-shaped Lissajous orbits, in which several spacecraft have traveled around the Sun-Earth L1 and L2 Lagrangian points and the Earth-Moon L1 and L2 points.
Enter the Horseshoe Orbit
A more recently-discovered path (which a 2011 Centauri Dreams article, Stable Orbit for a Newly Discovered Companion, discusses) is the horseshoe orbit, which got its name from its shape. [3] A small object in such an orbit goes around the Sun in a normal, low-eccentricity (close to circular) elliptical orbit in the direct (prograde) direction, but since its orbit has nearly the same period and shape as the orbit of a nearby planet (Earth, in the case of the horseshoe-orbiting asteroids discovered to date), gravitational interactions with Earth create the horseshoe path (which occurs only in the Earth-centered reference frame, as the asteroid orbits around the Sun normally). This celestial “dance” works as follows:
As the asteroid is about to pass the Earth in its slightly lower, more rapid orbit, the Earth’s gravity pulls it toward itself; this speeds up the asteroid, which causes it to move farther from the Sun (and thus into a higher orbit), and this then causes the asteroid to slow down, because objects in higher orbits move more slowly. In its higher, slower orbit, the asteroid then begins to drop behind the Earth, slowly “drifting” backwards all the way around the Sun (from the Earth’s perspective–the asteroid is orbiting the Sun in the same direct [prograde] direction as Earth, just more slowly). Many years later, as the asteroid again approaches Earth (from ahead of our planet this time), the Earth’s gravity slows down the asteroid, which causes it to fall into a lower, faster orbit around the Sun. Now moving faster than the Earth (inside Earth’s orbit), the asteroid slowly “drifts” all the way around the Sun again (moving forward this time, from Earth’s perspective), after which it repeats the whole horseshoe orbit cycle again. [4]
Image: A horseshoe orbit, showing possible orbits along gravitational contours. In this image, the Earth (and the whole image with it) is rotating counterclockwise around the Sun. Credit: Wikimedia Commons.
While other asteroids in horseshoe orbits with respect to Earth have been found before, their orbits aren’t long-term stable. Within a certain range of distances, orbital eccentricities, and velocities, however, stable horseshoe orbits are possible, and the asteroid 2010 SO16 (the subject of the Centauri Dreams article in Reference 3) is in one, having possibly followed its current orbit for up to two million years. In addition, it is possible–as 2010 SO16 might have done, as is mentioned in the article–for asteroids (or other objects, such as spacecraft) to librate (migrate) from Lissajous orbits around the Sun-Earth L4 or L5 Lagrangian points into stable horseshoe orbits. Migration from a horseshoe orbit back into a Lissajous orbit might also be possible, and what an unpowered asteroid could do, a self-powered space probe could likely also do–using little propellant.
Another unusual kind of orbit is the quasi-satellite orbit, in which NEAs (Near-Earth Asteroids) have also been discovered. [5] A quasi-satellite is in an orbit around the Sun that has a 1:1 resonance with the orbit of a particular planet. This causes the quasi-satellite to stay close to that planet over many orbital periods. A quasi-satellite’s orbit has the same period as the planet’s orbit, but the quasi-satellite’s orbit has a different–usually greater–eccentricity than the planet’s orbit. As observed from the planet, the quasi-satellite appears to move in an oblong retrograde loop around the planet, although both bodies are orbiting the Sun in direct (prograde) orbits.
Orbital Dynamics and ‘Fuzzy Boundaries’
Pioneer E (which would have been named Pioneer 10 if it had not been lost in its failed launch on August 27, 1969) was the fifth and last of the series of solar-powered, drum-shaped Sun-monitoring interplanetary probes that began with Pioneer 6 in December of 1965, and Pioneer E was intended to orbit the Sun as a quasi-satellite of Earth. Had it reached its planned solar orbit, Pioneer E (which was launched–and lost–with the TETR C test and training satellite, the intended third “practice” satellite for the Apollo tracking and communications network) would have passed inside and outside the Earth’s orbit, alternately speeding up and slowing down relative to Earth. This would have kept Pioneer E within 16 million kilometers (10 million miles) of Earth during the spacecraft’s design lifetime of from six months to two and one-half years. [6] (It would likely have operated for much longer than two and one-half years, as its sister probes Pioneer 6 – 9 demonstrated.)
Image: Artist’s conception of the Pioneer 6-9 spacecraft. Credit: NASA.
Orbit changes could be done using even less propellant (virtually none, in some cases) by employing Dr. Edward Belbruno’s principle of gravitational “Fuzzy Boundaries,” which involve the physics of chaos. [7, 8, and 9] This was first demonstrated in 1991 after Japan’s first lunar probe, the combined Hiten/Hagoromo spacecraft, ran into difficulties. Launched on January 24, 1990, the craft was injected into a highly-eccentric elliptical Earth orbit that passed beyond the Moon. The tiny Hagoromo lunar orbiter separated from Hiten during its first lunar swing-by and fired its solid propellant retro-rocket as the vehicles passed the Moon; while Hagoromo entered lunar orbit as intended, its radio transmitter failed when its retro-rocket fired (optical telescopic observation from Earth confirmed its entry into lunar orbit), which rendered it scientifically useless. [10] On March 19, 1991, Hiten performed the first-ever aerobraking maneuver, skimming the Earth’s atmosphere to change its orbit.
Having learned of Hagoromo’s transmitter failure, Edward Belbruno approached ISAS (the Institute of Space and Aeronautical Science) and offered to help them get their still-functioning Hiten lunar flyby spacecraft into lunar orbit. The probe, which was in a highly-eccentric Earth orbit, was moving much too fast during its lunar flybys to brake into lunar orbit using its onboard propellant. But by utilizing his “Fuzzy Boundaries” method, which involved using the combined gravity of the Moon and the Earth, on October 2, 1991 Hiten’s flight controllers were able to maneuver the probe into a preliminary, temporary lunar orbit using almost no propellant. After that, Hiten was targeted to fly through the Earth-Moon L4 and L5 points to collect data on any meteoric dust that was thought to possibly have accumulated there (none was detected). On February 15, 1993, Hiten was directed into a permanent lunar orbit, where it remained until it was deliberately crashed on the lunar surface on April 10. [11]
Image: An artist’s conception of the Hiten spacecraft. Credit: JAXA.
A Panoply of Applications
Stable horseshoe solar orbits and quasi-satellite solar orbits–entered and/or exited with the aid of Dr. Belbruno’s “Fuzzy Boundaries” method, making use of planetary as well as solar gravity–would be useful for Pioneer 6 – E type solar monitoring probes, which could observe portions of the Sun that cannot be seen (at any given time) from Earth. They could also, in concert with solar observations from Earth (or from Earth satellites), make stereo observations of solar features at many places along their horseshoe or quasi-satellite orbits. These same solar probes could also, as the Sun-orbiting Pioneer 7 interplanetary probe did, encounter and examine comets that pass through or near their orbits (flybys of asteroids that pass them would also be possible). If necessary, such probes could modify their horseshoe or quasi-satellite orbits (speeding up or slowing down, as needed) in order to make closer flybys of comets and asteroids (and later return to their original orbits) using very little propellant. Or, the probes could utilize solar sail propulsion (a simplified heliogyro sail should work nicely) to make such orbit changes, using no propellant at all.
Another application for horseshoe and quasi-satellite solar orbits would be to place NEO (Near-Earth Object) space telescopes in such orbits, much closer to the Sun than Earth’s distance. These locations would enable the spacecraft to see Earth-crossing NEOs whose orbits keep them mostly inside Earth’s orbit, and objects that could become dangerous to Earth in the future (via gravitational encounters with Venus and/or Mercury) would also be visible to these spacecraft. (To telescopes on or near the Earth, the sunlit sides of these small, often dark-colored objects face away from our planet, making them virtually impossible to see in the Sun’s glare, and Earth-based telescopes could never search for them in a truly dark sky because they would never be far from the Sun.) The B612 Foundation and its aerospace industry partner Ball Aerospace plan to send their NEO-seeking Sentinel space telescope to a Venus-like solar orbit for this reason. [12 and 13]. A horseshoe orbit or a quasi-satellite orbit “threaded around” Venus’ orbit about the Sun could reduce the necessary Delta-V (and thus the spacecraft’s launch vehicle and onboard propellant requirements) by utilizing Venus’ gravity to help establish–and later maintain by itself–either type of orbit for the Sentinel spacecraft.
Image: The Sentinel Space Telescope, being built by the B612 Foundation. Credit: B612Julie (Own work) [CC BY-SA 4.0 (http://creativecommons.org/licenses/by-sa/4.0)], via Wikimedia Commons.
Closer to home, Earth-centered horseshoe orbits–in which evenly-spaced communication, weather, or Earth resources satellites could “cycle” around the Earth as if on a circular conveyor belt (with two sets of spacecraft, on the inner and outer edges of the “belt”)–could provide global coverage not only of Earth, but they could also serve as communication relays for the lunar farside and for the Earth-Moon L2 point behind the Moon. (For circum-terrestrial horseshoe orbits, the Moon’s gravity would serve the same function that the Earth’s gravity does for Sun-centered horseshoe orbits that are “threaded around” Earth’s orbit about the Sun.) They could also provide close-up lunar observation to monitor time-variant lunar phenomena (the lunar “dustosphere’s” monthly cycling under the influence of Earth’s magnetotail, lunar meteorite impacts during meteor showers, TLP [the luminous Transient Lunar Phenomena], etc.).
Surprisingly, even low-cost suborbital interplanetary missions are possible. In addition to gathering data on the time-variant phenomena of the interplanetary environment, they could also collect dust, ice, and gas samples from comets that pass relatively close to Earth. NASA’s simple, inexpensive solid propellant Scout satellite launch vehicle, manufactured by LTV (Ling-Temco-Vought) using existing “off-the-shelf” rocket motors, was also used for several high-altitude suborbital probe missions that reached tens of thousands of kilometers into space. [14] (A rocket that ascends to an altitude of one Earth radius or higher is considered a space probe rather than a sounding rocket, because reaching one Earth radius requires a rocket velocity that is equal to Low Earth Orbit [LEO] orbital velocity.) The U.S. Air Force’s Blue Scout vehicles (which were similar to the NASA Scout vehicles for the most part, but were somewhat different because they were produced by a different contractor, the Ford Motor Company’s Aeronutronic Division) also flew numerous probe missions. [15 and 16] One in particular, a Blue Scout Junior launched from Cape Canaveral on August 17, 1961, reached an altitude of 225,000 kilometers (140,000 miles)–more than halfway to the Moon–on a suborbital flight lasting days. Unfortunately, the payload’s transmitter failed during the final (fourth) stage’s burn, rendering the flight scientifically useless. [17 and 18]
Image: The Blue Scout Junior. Credit: Peter Alway/Encyclopedia Astronautica: http://www.astronautix.com/index.html.
In his 1957 book The Making of a Moon: The Story of the Earth Satellite Program (and in its 1958 post-Sputnik revised second edition), Arthur C. Clarke pointed out that by launching suborbital vehicles at velocities approaching Earth’s escape velocity, their payloads could reach altitudes of millions of miles before falling back to Earth. [19] Interestingly, the altitudes achieved begin to increase dramatically at only 35,000 kilometers per hour (22,000 miles per hour), significantly below Earth’s escape velocity. As he wrote: “A rocket launched vertically at 22,000 miles an hour–or four thousand miles an hour faster than a satellite–would reach an altitude of about fifteen thousand miles before gravity checked its speed and it fell back to Earth. Slight further increases in velocity would give altitudes of millions of miles, until at the critical speed of 25,000 miles an hour the rocket never came back at all.”
Such vehicles could be very small–the 7.3-meter (24-foot) long, balloon-launched Project Farside probe rockets of the late 1950s, which reached nearly orbital velocity and rose to altitudes of between 3,200 and 5,000 kilometers (2,000 and 3,100 miles) with 1.4 to 3.3 kilogram (3 to 5 pound) payloads, could have reached the vicinity of the Moon with the addition of a fifth stage, which was proposed. [20] But this proposal was not proceeded with, possibly because the electronics technology of those days likely wouldn’t have enabled such small payloads to return meaningful data from the Moon’s distance (the frequent failures of the Farside vehicles’ payload transmitters also didn’t encourage much confidence in more ambitious ventures). But today a full suite of instruments, an S-band or X-band telemetry transmitter, and their solar cell or battery power supply could be accommodated in payloads of that mass range.
Image: Working on Project Farside. Credit: Parsch, Directory of U.S. Military Rockets and Missiles: http://www.designation-systems.net/dusrm/app4/farside.html.
Existing high-performance multi-stage sounding rockets could, if topped with multiple high-velocity stages, boost heavier payloads to such velocities (similar vehicles have boosted artificial meteors to velocities far in excess of escape velocity, beginning in 1957). [21 and 22] Such “souped-up” sounding rockets, or small–particularly air-launched satellite launch vehicles with additional upper stages, such as Orbital Sciences Corporation’s Pegasus XL and the upcoming Boeing ALASA (Airborne Launch Assist Space Access) system–could loft small suborbital interplanetary probes. [23 and 24] This capability would make possible low-cost, rapid comet sample return missions to “targets of opportunity,” comets such as IRAS-Araki-Alcock and Hyakutake that pass within a few million kilometers of Earth.
Image: The Pegasus XL launch vehicle operated by Orbital Sciences Corporation. Credit: NASA.
The recoverable portion of the spacecraft could use a deployable aerogel particle collector that would be housed in a small, blunt re-entry heat shield similar to that of the Pioneer Venus Small Probes or the Japanese Hayabusa and Hayabusa 2 asteroid sample return probes. The expendable section of the spacecraft, which would burn up upon re-entry into the Earth’s atmosphere, would carry fields and particles instruments and an imaging system. At other times, such suborbital probes could collect intact meteoroids from meteor shower streams for return to Earth, and/or they could gather data on the far regions of Earth’s magnetosphere and magnetotail, including their interactions with the solar wind and the solar magnetic field. Since the parent bodies of many meteor shower streams are now known (most originate from comets–a few are from asteroids), suborbital probes would offer inexpensive, frequent, and regular opportunities for collecting samples of these objects.
By substituting subtlety and cleverness for brute force, and by letting some mission targets come to their probes more than vice-versa, many new, scientifically useful, and inexpensive space missions would become practical and affordable. In addition to garnering new knowledge, such missions would also provide more frequent opportunities for young scientists, engineers, and orbital dynamicists to gain hands-on experience in designing and executing deep space missions–experience that would be of great help to them when the time comes to tackle the more ambitious outer solar system and observatory missions that NASA hopes to fly in the coming decades.
——-
References
1. Pioneer Venus Project Information, National Space Science Data Center website: http://nssdc.gsfc.nasa.gov/planetary/pioneer_venus.html
2. Pioneer 6, 7, 8, and 9, Wikipedia article: https://en.wikipedia.org/wiki/Pioneer_6,_7,_8,_and_9
3. Stable Orbit for a Newly Discovered Companion, Centauri Dreams article: https://centauri-dreams.org/?p=17484
4. Horseshoe orbit, Wikipedia article: https://en.wikipedia.org/wiki/Horseshoe_orbit
5. Quasi-satellite, Wikipedia article: https://en.wikipedia.org/wiki/Quasi-satellite
6. TRW Space Log, Winter 1969-70, Vol. 9, No. 4, Pioneer E, TETR C entry on pages 40 – 43.
The National Space Science Data Center http://nssdc.gsfc.nasa.gov/ has a Pioneer E mission page at http://nssdc.gsfc.nasa.gov/nmc/spacecraftDisplay.do?id=PIONE.
7. Edward Belbruno, Wikipedia article: https://en.wikipedia.org/wiki/Edward_Belbruno
8. Edward Belbruno : Mathematics, Astrophysics, Aerospace Engineering (Edward Belbruno’s Official Website): www.edbelbruno.com
9. SpaceRoutes.com website: http://www.spaceroutes.com/intro.html
10. Hiten (Muses-A) JAXA webpage: http://www.isas.jaxa.jp/e/enterp/missions/hiten.shtml
11. Hiten, Wikipedia article: https://en.wikipedia.org/wiki/Hiten
12. Sentinel Space Telescope, Wikipedia article: https://en.wikipedia.org/wiki/Sentinel_Space_Telescope
13. Sentinel Mission website (mission overview page): http://sentinelmission.org/sentinel-mission/overview/
14. LTV (Vought) SLV-1 Scout, Designation Systems article: http://www.designation-systems.net/dusrm/app3/lv-1.html
15. Ford RM-89 Blue Scout I, Designation Systems article: http://www.designation-systems.net/dusrm/app1/rm-89.html
16. Ford RM-90 Blue Scout II, Designation Systems article: http://www.designation-systems.net/dusrm/app1/rm-90.html
17. Ford RM-91 Blue Scout Junior, Designation Systems article: http://www.designation-systems.net/dusrm/app1/rm-91.html
18. Blue Scout Jr, Encyclopedia Astronautica article (with launch chronology): http://www.astronautix.com/lvs/bluoutjr.htm
19. The Making of a Moon: The Story of the Earth Satellite Program by Arthur C. Clarke, pages 149 – 150 (First Edition, Published 1957 by Harper & Brothers Publishers, New York, NY, Library of Congress catalog card number: 57-8187 [a post-Sputnik revised edition, the same book with that update, was published in 1958])
20. Aeronutronics Farside, Designation Systems article: http://www.designation-systems.net/dusrm/app4/farside.html
21. Possible Challenge to Sputnik on Unmanned Spaceflight website: http://www.unmannedspaceflight.com/lofiversion/index.php/t1955.html
22. The First Shots Into Interplanetary Space by Professor Fritz Zwicky, California Institute of Technology Library website: http://calteches.library.caltech.edu/181/1/zwicky.pdf
23. Boeing to Design DARPA Airborne Satellite Launch Vehicle, Boeing.com website: http://www.boeing.com/features/2014/03/bds-darpa-contract-03-27-14.page
24. DARPA’s ALASA space launch system from airplane, wordlessTech.com website: http://wordlesstech.com/darpas-alasa-space-launch-system-from-airplane/
One of my Fav Astrodynamics papers
https://yellowdragonblogdotcom.files.wordpress.com/2015/08/okutsu_cassini_saturn_escape.pdf
dual planet missions are possible
Reducing energy requirements reminds me of my old British geography text books where we learned wind and ocean current patterns. Yes, that was to explain climate, but also this knowledge was needed when the British Empire had sailing ships and needed to find the fastest routes to her foreign ports. How much of that knowledge was no longer needed in the age of steamships.
Space travel today is still in the early stages, and like those early steam ship experiments where clipper ships were still faster, it may be that clever use of gravity and solar electric/sail propulsion will prove the best way to get to distant targets , rather than the brute force of chemical rockets, especially when fuel dumps have yet to be created.
I’d like to learn more about this, especially when coupled with high Isp, low thrust propulsion systems, that can have low mass ratios to deliver useful payloads.
Dancing in the dark redux: Recent Russian rendezvous and proximity operations in space
In the last few years, Russia has carried out a number of missions to test rendezvous and proximity operations, both in low Earth orbit and geosynchronous orbit. Brian Weeden describes what is known about these efforts, and the policy implications of such tests given similar missions by American spacecraft in the past.
Monday, October 5, 2015
http://www.thespacereview.com/article/2839/1
Earth Moon Lagrange 2 (EML2) is a very interesting location. I devoted a blog post to EML2: http://hopsblog-hop.blogspot.com/2015/05/eml2.html
In terms of delta V, EML2 is .9 km/s from Trans Mars Injection (TMI) using the Farquhar route. If using a fuzzy route, EML2 can be within .6 km/s of TMI. EML2 is about 2.5 km/s from the moon. EML2 is less than .2 km/s from many Near Earth Asteroids.
In the blog post I portray a 74 day path from Low Earth Orbit (LEO) to EML2 than takes about 3.1 km/s. The Farquhar route from LEO to EML2 takes about 9 days and costs about 3.5 km/s. In both cases the lion’s share of delta V is achieving a high apogee — this takes about 3.1 km/s. Compared to the Farquhar route, only .4 km/s is saved by exploiting weak stability boundaries from EML2 for ballistic capture.
In 3 body mechanics, the mass parameter ? is an important quantity (not to be confused with G*mass central body, the more usual use of ?). The 3 body ? is (mass orbiting body)/(mass orbiting body + mass central body). A big ? makes for dramatic Weak Stability Boundaries (WSBs) emanating from the L1 or L2 necks. I talk about this at http://hopsblog-hop.blogspot.com/2015/06/mass-parameter-and-itn.html.
A big ? is what makes the L1 and L2 necks of the earth-moon system interesting. Other big ?’s: sun-Jupiter, Pluto-Charon, Jupiter-Ganymede as well as other gas giant-big moon pairs.
But the ? for sun-small rocky planets is tiny. WSBs aren’t useful for getting us from sun-Earth Lagrange 2 to sun-Mars Lagrange 1. Belbruno’s co-author Toppotu has admitted this. Also Shane Ross, one of the architects of the Interplanetary Superhighway. See http://hopsblog-hop.blogspot.com/2015/04/potholes-on-interplanetary-superhighway.html
There was an article about 10 years ago in “Discover” magazine on the problems concerning high fuel usage in space travel. It looked at the problem of going to the moon without much fuel. Someone figured out at JPL labs that if you sent the vehicle toward the sun, it would reach a point where it would began to return toward the earth fly by the earth and reach the moon’s orbit with just enough impetus to allow it to achieve orbit around the moon with virtually no fuel. Quite an interesting concept.
A very interesting post but I an not serious but Sirius this evening I will tell you people about my new pet theory :
Maybe the game of throne’s planet is in a kind of lissajous orbit around the L4 or L5 point of a Jupiter like big planet ! A troyan planet where the seasons are unpredictable because they are not caused by the inclinaison of the Axis of the world but by the variable distance from the sun. As these seasons are years long it must orbit longer orbits around a sun brighter than ours , so why not around Sirius !
Writen under the influence of green tea !
I love this stuff. I want to be reincarnated as a starship navigator.
Dear Jason
A very nice review of interesting possibilities. If humanity is ever to break free from the Earth-Moon system, understanding of these interesting orbits and the ways to exploit them will be most useful.
Regards, Greg
Charlie wrote: “Someone figured out at JPL labs that if you sent the vehicle toward the sun, it would reach a point where it would began to return toward the earth fly by the earth and reach the moon’s orbit with just enough impetus to allow it to achieve orbit around the moon with virtually no fuel. ”
Yes, firing a payload to the edge of earth’s Hill sphere at the right time can exploit the sun’s tidal influence at apogee to raise perigee to the moon’s neighborhood for ballistic lunar capture.
However getting a high apogee from LEO takes 3.1 km/s. True for Hiten as well as Apollo. The apogee burn saved by ballistic capture is in the neighorhood of .5 km/s.
David S. F. Portree writes:
Music to my ears. You’re speaking to someone who cut his teeth on Starman Jones and thought ‘astrogator’ was the job description of choice!
I’ll be pleased to awaken one day soon and stand up–tentatively at first–on four cloven hooves, while drinking in the sensations from my single horn…and I won’t need a spaceship to explore any world (or realm) that attracts my interest… Having had no fewer than three medical appointments today, it was so nice to come home to find not only the article, but all of your comments and compliments–Thank You! The links are very interesting, and I hope the ideas in them will be implemented; we need to learn to use the “currents and winds” of space, to save money and effort. Also:
Alex Tolley’s description is spot-on. Hugo Eckener, who headed the Zeppelin company after Count Ferdinand von Zeppelin died, was also a Zeppelin (rigid airship) captain, and he flew in seemingly random directions. But his courses weren’t random at all–he was flying toward storms and other cyclonic formations, to pick up fuel- and time-saving tailwinds by passing them on the appropriate side. In fact, the requirements of the passenger Zeppelin service led to the first embryonic weather forecasting service. Likewise:
Minimum-cost space missions that utilize rather similar gravitationally-advantageous pathways may lead to high-precision mapping services for charting the various bodies’ gravitational fields (including their harmonics, mascon effects, etc.) and their ever-shifting interactions.
Paul, David, maybe you’d enjoy The Astrogator’s Guild: http://astrogatorsguild.com/
Speaking of unusual orbits and missions that could utilize them, the “figure eight” Earth-Moon orbit, which the Soviet Union’s Luna 3 spacecraft used in October of 1959 (after it fell silent, not long after photographing the lunar farside, it followed that path without any trajectory adjustments for about six months before it finally re-entered the Earth’s atmosphere), could have multiple applications today:
JPL is developing the INSPIRE CubeSat-based (3U CubeSat, if memory serves) lunar mission, to demonstrate these very small spacecraft’s utility for deep-space missions. As Arthur C. Clarke pointed out on page 149 of “The Making of a Moon: The Story of the Earth Satellite Program,” a lunar probe in such a figure eight orbit could store its lunar data and images and transmit them when it was only about a thousand miles from Earth, which would require only *half a millionth* of the power needed to send the same information all the way back from the Moon! This would greatly reduce the probe’s power supply and transmitter output power requirements. Also:
Since such figure eight orbits can be semi-permanent (as Luna 3 demonstrated), a propellant-less propulsion system such as a solar sail, a magnetic sail, or an electrostatic tether could maintain such an orbit indefinitely. Therefore, not only probes, but translunar space stations in such figure eight Earth-Moon orbits should be practical, providing ready access to and from the surfaces of both bodies. (Plus, unmanned and manned interplanetary missions could depart from and return to such stations using relatively little Delta-V.) By selecting the figure eight orbit’s parameters carefully and utilizing Dr. Edward Belbruno’s “Fuzzy Boundaries” (Weak Stability Boundaries) maneuvers, the propellant requirements for all missions to and from translunar space stations could be further minimized. In addition:
Another 1950s concept–which has been employed only once, to my knowledge, in ESA’s ion propulsion Gravity Field and Steady-State Ocean Circulation Explorer satellite (GOCE, see: http://search.lycos.com/images/?q=GOCE+satellite&keyvol=00f6bab5fd194ce8e457 )–would also be useful for some planetary missions. Many space flight books of that era (including Arthur C. Clarke’s “The Making of a Moon,” in its 12th chapter–Erik Bergaust’s and William Beller’s book “Satellite!” was another) discussed Kraft Ehricke’s concept of the “satelloid,” a ‘forced-orbit’ vehicle–usually envisioned as being a winged rocket plane–that would circle the Earth at altitudes of between 90 miles and 150 miles or so, after being lofted by a conventional multi-stage launch vehicle. A satelloid would use either a tiny rocket engine (which would consume only about seven pounds of propellant per orbit, even for a multi-ton manned satelloid), ion propulsion (as GOCE did), or an ionospheric “ramjet” that would use an electrically-catalyzed O + O –> O2 reaction, using the monatomic oxygen of the Earth’s exosphere as a fuel and working “fluid” to produce the tiny thrust needed to maintain the satelloid’s orbit. Now:
For missions in which it would be desirable (as was the case with the Pioneer Venus Orbiter mission) to sample the upper atmosphere of the target planet, a satelloid probe would be ideal. Unlike the Pioneer Venus Orbiter, which dipped into Venus’ upper atmosphere only at the periapsis of each of its highly-eccentric 24-hour elliptical orbits, a satelloid could sample Venus’ atmosphere–and probably down to lower altitudes–during entire orbits around both the day and night sides of the planet. This would provide a greater breadth and volume of data on Venus’ ionosphere, whose parameters vary greatly from day to night (and even more so than Earth’s ionosphere, because Venus lacks a magnetic field). *Any* planet or moon with an atmosphere could be investigated in this way using satelloids, which could also conduct normal orbiter-type imaging and fields & particles measurements. In addition:
If a landing on the surface, or even just an examination of the atmosphere at lower altitudes (possibly with a return to orbit afterward) is desired, a winged satelloid could also perform these mission profiles. (For simpler, upper atmosphere-sampling missions, wingless satelloids [GOCE was of this configuration; its solar panels were shaped like fins, to provide aerodynamic stability in the upper atmosphere] would suffice.)
Here is an interesting YouTube clip of the interplanetary freeway, provided you are prepared to spend more time the amount of fuel needed to move between celestial objects is much smaller. Perhaps we can have large space hotels moving along these freeways and all you need to do is get transport to them for food, drink and protection and then jump off again at your destination.
https://www.youtube.com/watch?v=c00f1DiHygI
@Hop David
can you tell me, is the Astrogator guide that you pointed to in your link, is that tool based upon REALISTIC navigation software or is it a program which is merely used to emulate what navigation would be supposedly like in space ? Do you happen to know ?
@Michael – good clip. Thanks.
@Jason – using this approach, what would be a low energy cost source of water? Would Jupiter or Saturn be better than Ceres?
These low energy pathways seem ideal for low thrust electric engines or sails, allowing small sails or engines to apply the gentle push to move between the gravity tubes. Where time is not so important, I’m wondering if this is the best way to set up water depots at EML1 or EML2 or even LEO for propulsion and life support.
Hop David, thanks for the tip about the Astrogator’s Guild!
Charlie, not sure which tool you’re talking about. Mike and John plan trajectories. They worked on the LADEE mission.
Alex, the closest water in terms of delta V are carbonaceous ivuna asteroids in earth like orbits. Then the lunar cold traps.
Given the tiny mass parameter for sun-earth, there aren’t useful interplanetary WSBs emanating from Sun Earth Lagrange 1 or Sun Earth Lagrange 2.
There can be interesting interactions between the sun earth L1/2 and the earth moon L1/L2 that would be helpful in sending payloads on their way.
But there aren’t any “tubes” from earth to Mars. Or from earth to Jupiter. Or from earth to Saturn.
Given Ceres’ fast spin (a 9 hour sidereal day) and shallow gravity well, Ceres would be very amenable to space elevators. This might be a way Ceres could export water should water become a Ceres commodity.
Michael wrote:
“Here is an interesting YouTube clip of the interplanetary freeway, provided you are prepared to spend more time the amount of fuel needed to move between celestial objects is much smaller. Perhaps we can have large space hotels moving along these freeways and all you need to do is get transport to them for food, drink and protection and then jump off again at your destination.
https://www.youtube.com/watch?v=c00f1DiHygI ”
Thank you! Wikipedia also has an article on the Interplanetary Transport Network (ITN, see: https://en.wikipedia.org/wiki/Interplanetary_transport_network ). Also (to answer Alex’s question):
Depending on the Delta-V and the trip durations to and from it, I’d go after a comet (or an extinct comet “asteroid”) before Ceres, Jupiter, or Saturn. In addition:
Dr. Edward Belbruno and his colleagues have found a new fuel-less Mars ballistic capture trajectory that allows launches to Mars at *any* time (no more launch windows!) and cuts the total propellant requirement by about 25%! Like the horseshoe or quasi-satellite orbit solar orbiting monitor probe/comet flyby probe spacecraft that I mentioned in the article, Ed Belbruno’s and his colleagues’ new Mars transfer trajectory (which could be used to reach *any* planet or moon, including our Moon) “lets Mars do most of the moving” to capture an orbiter. Below is a link to a “Scientific American” article on this:
“A New Way to Reach Mars Safely, Anytime and on the Cheap” http://www.scientificamerican.com/article/a-new-way-to-reach-mars-safely-anytime-and-on-the-cheap/
I hope this information will be helpful.
I forgot to add before (in response to what Alex Tolley wrote, in part):
“These low energy pathways seem ideal for low thrust electric engines or sails, allowing small sails or engines to apply the gentle push to move between the gravity tubes. Where time is not so important, I’m wondering if this is the best way to set up water depots at EML1 or EML2 or even LEO for propulsion and life support.”
By using lunar space elevators originating from the Moon’s polar regions (the elevators could be made of existing high-strength fibers such as Kevlar or Spectra, and they would curve down [or up] to the Moon’s equatorial plane), the Moon’s permanently-shadowed polar craters could be used as cryogenic storage areas for cometary and asteroidal water, which could be brought to the Earth-Moon L1 and/or L2 point and “winched down” the elevators to the surface. Also:
A Falcon 9 could carry a rolled-up lunar space elevator (a company–whose name escapes me at the moment–is planning this), which would extend beyond the Earth-Moon L1 or L2 point (for mass counter-balancing) from near either lunar pole. Spacecoaches and/or other low-thrust interplanetary spacecraft could rendezvous at L1 or L2 depots to drop off ice they’d extracted elsewhere, or to take on water, LOX/LH2, and other ice-derived commodities (ammonia, methane, etc.) from cometary or asteroidal ice that had been stored in shadowed lunar craters earlier (or that had been made from the “native” lunar polar ice).
This Pdf explain a little more about the interplanetary highway,
http://www.gg.caltech.edu/~mwl/publications/papers/IPSAndOrigins.pdf
If we had small magsails or solar sails attached to spacecraft we could use these highways for little or no propellant usage.
Jason wrote “Dr. Edward Belbruno and his colleagues have found a new fuel-less Mars ballistic capture trajectory that allows launches to Mars at *any* time (no more launch windows!) and cuts the total propellant requirement by about 25%! ”
Belbruno has done so such thing.
See http://hopsblog-hop.blogspot.com/2015/04/potholes-on-interplanetary-superhighway.html There’s a section titled “Mars ballistic capture by Belbruno & Toppotu”.
Shane Ross commented. He acknowledges that the Interplanetary Super Highway is not practical for travel to Mars.
It is possible that at the EL1 and EL2 positions a fleet of equally spaced telescopes communicating to a central craft could orbit around the Lagrange points at such a distance from its centre that they could start to use the gravitational lens effect of the sun to amplify the light signal, not a lot mind you. However adding more scopes over time would increase the light gathering power substantially.
@Hop David, you wrote below the following:
“Charlie, not sure which tool you’re talking about. Mike and John plan trajectories. They worked on the LADEE mission.”
Your reply served only to open several NEW QUESTIONS that I now have. You said the above, the following: “Paul, David, maybe you’d enjoy The Astrogator’s Guild: http://astrogatorsguild.com/”
THAT’S the tool that I’m speaking about that you just mentioned in the above reply.
I had asked ‘can you tell me, is the Astrogator guide that you pointed to in your link, is that tool based upon REALISTIC navigation software or is it a program which is merely used to emulate what navigation would be supposedly like in space ? Do you happen to know ?’ What I meant when I said that comment was is the Astrogator guide an ACTUAL computational device that is used in REAL space navigation OR is it just meant to be a simulation of what it would be to perform a faux calculation of an orbit ? That’s what I meant by my question.
The NEW info that you provided concerns what you said here: ‘Mike and John plan trajectories. They worked on the LADEE mission.’ WHO is Mike and John ? I haven’t read all the comments so I don’t know who you were referring to, and also how do you happen to know these gentlemen and know that they worked on the trajectories on the LADEE mission ? Not doubting you here. I’m just trying to catch up in the comments sections and learn a little bit more about these two gentlemen that you mentioned and their connection to this area of trajectory determinations. I don’t read every comment, so forgive me that if I happen to miss something here or there in the welter of information that’s on this site.
Hop David – forgot to ask, are YOU involved in the determination of space trajectories ? If you are, I would like to address certain questions to you if you would be available to answer some inquiries. Appreciate your time.
Charley,
Astrogator’s Guild is a blog by Mike Loucks and John Carrico, two professional orbital dynamics guys. At the moment I can’t find their C.V.s or resumes.
In their blog they talk about different orbits and orbital mechanics.
If I remember right, they use STK/astrogrator for their software, which is for professionals.
Myself, I am just an amateur. I love geometry and space exploration and have been studying orbital mechanics for a few years. The tools I use are Microsoft Excel, Adobe Illustrator and pencil and paper to help me visualize. If you want to ask me questions my email is hop4143 at gmail dot com
Hop David wrote:
“Jason wrote “Dr. Edward Belbruno and his colleagues have found a new fuel-less Mars ballistic capture trajectory that allows launches to Mars at *any* time (no more launch windows!) and cuts the total propellant requirement by about 25%! ”
Belbruno has done so such thing.
See http://hopsblog-hop.blogspot.com/2015/04/potholes-on-interplanetary-superhighway.html There’s a section titled “Mars ballistic capture by Belbruno & Toppotu”.
Shane Ross commented. He acknowledges that the Interplanetary Super Highway is not practical for travel to Mars.”
Unless “Scientific American’s” editorial standards have declined precipitously (they published the Mars transfer article), I’ll go with their judgement on the matter. And Shane Ross’ categorical comment that the Interplanetary Super Highway is not practical for travel to Mars (Arthur C. Clarke would have smiled indulgently at that, having found that such statements usually turn out to be wrong) reminds me of Buzz Aldrin’s Mars Cycler orbits, which many in the field said wouldn’t work…until he found and demonstrated mathematically that they would… This doesn’t mean, of course, that Belbruno et al’s new Mars transfer trajectory *has* to work (even the best minds come up with a “dry hole” from time to time), but given his track record, I wouldn’t bet against him.
So what I gather from Hop’s comment and his blog post is that the IPS doesn’t really exist for the many locations claimed. Is that correct? This argument is bolstered by the Astrogator’s Guild authors. Is that correct?
OTOH the Lo paper is making the claim that many bodies can be reached by the IPS.
Is there any way to resolve this issue?
From my perspective, what we are looking for is ways to significantly reduce the energy requirements of interplanetary travel, especially for robotic instruments and cargo payloads. This is desirable while our propulsion methods are still relatively low energy, although this may change with high energy propulsion, rather like the transition from sail to steam ships.
The IPS also reminds me of how living organisms use similar approaches, for example birds can fly long distances using coastal updrafts to almost eliminate flapping, an approach mimicked by glider pilots. It is elegant.
Although there may not be a practical route to Mars via a IPS tube it does not mean the concept is dead. I mean there are plenty of other uses for the technic for instance communication systems and observation instruments. Both will be vital to our expansion into the cosmos and could be used for the trip to Mars so not as much equipment would be needed at Mars reducing fuel requirements.
Alex, these pro- and anti-IPS arguments remind me of the “Gold Dust Theory” affair (regarding astronomer Thomas Gold’s warnings that lunar landing spacecraft would sink out of sight, into a thick layer of dust). Patrick Moore and many other lunar observers gave Gold’s idea no credence, and they advanced sensible counter-arguments based upon their telescopic observations of the Moon’s surface, but Moore wrote that there was only one way to find out for sure–send a soft-landing probe. Also:
I would suggest that the various IPS trajectories be tested as well, by sending probes along them. Simple 3U or 6U CubeSat-based spacecraft, fitted with either onboard main propulsion chemical or electric thrusters (these are in development for CubeSat-based probes) or solar sails, would make their missions to the various inner solar system bodies scientifically worthwhile even if some of the IPS trajectories don’t “work as advertised.”
Belbruno’s ballistic Mars capture uses the standard Trans Mars Injection burn (read the paper).
For Mars rendezvous, Belbruno does a 2 km/s burn at ~1.5 A.U. aphelion.
Doing the burn deep in Mars gravity well, Mars capture can be achieved with .7 km/s. Belbruno evidently hasn’t heard of the Oberth benefit.
From Shane Ross’ comment: “I suspect that gravitational corridors which naturally connect Earth-bound orbits with Mars-bound orbits using no-fuel do exist, but might take a long time to achieve (I’m thinking thousands of years of flight time between the two planets)”
Did you get that? He *suspects* they exist. But if they do it’ll take thousands of years.
Low thrust trajectories using ion engines are often conflated with the Interplanetary Transportation Network. Traveling using ion engines also takes lots of delta V. But mass fraction is better because of higher exhaust velocity. Not the same as ITN at all.
Same with solar sails. Pressure from sunlight can accomplish a lot of delta V. The use of solar sails doesn’t mean you’re riding a delta V free route along tubes emanating from L1 or L2 necks.
Jason, regarding your defense of the ITN: I see no math in your wall of text.
Alex, Lo is correct. Under some circumstances WSBs from L1 and L2 necks are useful. But not between earth and Mars.
It depends on the mass parameter. See http://hopsblog-hop.blogspot.com/2015/06/mass-parameter-and-itn.html
Jason, do you think Shane Ross is an addled naysayer of the ITN? Shane Ross is one of the *architects* of the ITN. Along with Marsden and Lo.
By all means, test the ITN with a cube sat. Send a cube sat along one of these pathways to Mars.
If you can find such a pathway, Ross, Lo and Marsden will love you. Folks have been tryng. The best I’ve seen is the Belbruno and Toppotu paper which actually takes more delta V than Mars capture exploiting the Oberth effect.
Hop David,
I am puzzled as to why this vexes you so much. I never questioned Shane Ross’s or anyone else’s intelligence, but only pointed out that what many say is impossible very often turns out not to be, which is why no such assertions should be accepted by researchers. Many “impossible” things that we take for granted today would never have come about had everyone listened to the “null-sayers” (Marconi’s development of inter-oceanic and inter-continental radio is just one example–the experts of his day told him that radio waves, like like waves, wouldn’t bend over the horizon). Also:
I want the solar system to become accessible–to humans as well as to robotic spacecraft (and I think all of us here do)–by the least expensive means that can be found, and engaging in uncalled-for tirades isn’t an effective way to get closer to that goal. Dr. Theodore Von Karman once lamented the *lack* of controversy at a space technology symposium, saying “How can we have progress without controversy?” But as rocket engineer G. Harry Stine (who provided that Von Karman quotation in his “Handbook of Model Rocketry”) pointed out, such controversy must be mannered (free from ad hominem attacks) if any progress is to come from it; otherwise, only personal enmity and division will result, which retards scientific and technological progress.
Wow! So many detailed and interesting post that it makes my head swim. It’s hard for me to follow every nuance of what everybody says. The best I can do to save myself here is to try to pick one or two posts and tried to get some more information. It was mentioned by J. Jason Wentworth that:
Jason wrote “Dr. Edward Belbruno and his colleagues have found a new fuel-less Mars ballistic capture trajectory that allows launches to Mars at *any* time (no more launch windows!) and cuts the total propellant requirement by about 25%! ”
Belbruno has done so such thing.
Did you mean to say, ‘Belbruno has done NO such thing.’? And as I just stated I haven’t been able to read all the back and forth post in detail. So is this no launch window scenario in actuality, or is it something that has to be the finessed to finally get it resolved?
One important question that I wanted to ask and I just remembered. While all these complicated and energy-saving trajectories are a desirable aspect to this particular subject, isn’t it also true that they might not be of such great use if were talking about human spaceflight ?
For example, a lot of these trajectories require a great deal of time to make full use of their energy savings and that would seem to have a tremendous negative impact on human passengers. I’m thinking here of boredom and also such things as resource conservation to accomplish a particular mission. It’s all good and well for our robot to make a voyage such as this, but it might strain the patience of humans far such a lengthy excursion.
Jason,
I fervently desire that humanity break free of the restraints that keep us chained to Cradle Earth. I’ve spent a great deal of time and effort looking for plausible ways this might happen.
Is an idea worthwhile? If so, how to bring it fruition? To this end, a thoughtful Devil’s Advocate is more helpful than a hundred mindless cheerleaders.
If an idea is found to be a waste of time, that allows us to invest our time and effort in notions with a better chance of success.
I welcome you to look at my arguments. I sometimes make errors. If you find a flaw in my math, I will be delighted. It would be wonderful if the ITN were the revolutionary tool many think it is.
But have you offered a thoughtful critique of my math? No.
So far you’ve painted a picture of Arthur C. Clarke smiling indulgently at naysayers. You suggest that since Thomas Gold’s “Gold Dust Theory” turned out to be wrong, my criticism of the ITN is also invalid.
I find your arguments to be insulting and condescending. Worse, having no math, they are a waste of my time. And time is becoming an increasingly precious commodity for me.
Charley, below–for you, and for anyone who might not have caught the link amongst all of the postings above–is the article that started all of the excitement (and for completeness’ sake, here is a link to it: http://www.scientificamerican.com/article/a-new-way-to-reach-mars-safely-anytime-and-on-the-cheap/ ). Now:
Since Dr. Edward Belbruno has demonstrated his celestial mechanics expertise by devising WSB (Weak Stability Boundary, also called “Fuzzy Boundaries”) low-energy trajectories that have been used successfully by spacecraft, I see no reason to doubt him–or “Scientific American,” who published the article–when he speaks about the new Mars transfer trajectory that the article is about (just as Burt Rutan, who has many aeronautical engineering achievements to his credit, was taken seriously when he said he would develop a reusable suborbital manned spacecraft, and his SpaceShipOne worked, just as he said it would). I certainly don’t think Dr. Belbruno or Mr. Rutan are infallible (even Einstein wasn’t able to get to a Grand Unification Theory), but given their track records, when they say that a given thing they’re working on *will* work, the odds are that they’re right. Here is the article:
“A New Way to Reach Mars Safely, Anytime and on the Cheap”
Ballistic capture, a low-energy method that has coasted spacecraft into lunar orbit, could help humanity visit the Red Planet much more often
By Adam Hadhazy | December 22, 2014
Getting spacecraft to Mars is quite a hassle. Transportation costs can soar into the hundreds of millions of dollars, even when blasting off during “launch windows”—the optimal orbital alignments of Earth and Mars that roll around only every 26 months. A huge contributor to that bottom line? The hair-raising arrivals at the Red Planet. Spacecraft screaming along at many thousands of kilometers per hour have to hit the brakes hard, firing retrorockets to swing into orbit. The burn can require hundreds of pounds of extra fuel, lugged expensively off Earth, and comes with some risk of failure that could send the craft careening past or even right into Mars.
This brute force approach to attaining orbit, called a Hohmann transfer, has served historically deep-pocketed space agencies well enough. But in an era of shrinking science budgets the Hohmann transfer’s price tag and inherent riskiness look limiting.
Now new research lays out a smoother, safer way to achieve Martian orbit without being restricted by launch windows or busting the bank. Called ballistic capture, it could help open the Martian frontier for more robotic missions, future manned expeditions and even colonization efforts. “It’s an eye-opener,” says James Green, director of NASA’s Planetary Science Division. “It could be a pretty big step for us and really save us resources and capability, which is always what we’re looking for.”
The premise of a ballistic capture: Instead of shooting for the location Mars will be in its orbit where the spacecraft will meet it, as is conventionally done with Hohmann transfers, a spacecraft is casually lobbed into a Mars-like orbit so that it flies ahead of the planet. Although launch and cruise costs remain the same, the big burn to slow down and hit the Martian bull’s-eye—as in the Hohmann scenario—is done away with. For ballistic capture, the spacecraft cruises a bit slower than Mars itself as the planet runs its orbital lap around the sun. Mars eventually creeps up on the spacecraft, gravitationally snagging it into a planetary orbit. “That’s the magic of ballistic capture—it’s like flying in formation,” says Edward Belbruno, a visiting associated researcher at Princeton University and co-author, with Francesco Topputo of the Polytechnic University of Milan, of a paper detailing the new path to Mars and the physics behind it. The paper, posted on arXiv, has been submitted to the journal Celestial Mechanics and Dynamical Astronomy.
“A delicate dance”
Ballistic capture, also called a low-energy transfer, is not in of itself a new idea. While at NASA’s Jet Propulsion Laboratory a quarter century ago, Belbruno laid out the fuel-saving, cost-shaving orbital insertion method for coasting probes to the Moon. A Japanese vessel, called Hiten, first took advantage in 1991, as did NASA’s GRAIL mission, launched in 2011.
Belbruno worked out how to let the competing gravities of Earth, the sun and moon gently pull a spacecraft into a desired lunar orbit. All three bodies can be thought of as creating bowl-like depressions in spacetime. By lining up the trajectory of a spacecraft through those bowls, such that momentum slackens along the route, a spacecraft can just “roll” down at the end into the moon’s small bowl, easing into orbit fuel-free. “It’s a delicate dance,” Belbruno says.
Unfortunately, pulling off a similar maneuver at Mars (or anywhere else) seemed impossible because the Red Planet’s velocity is much higher than the Moon’s. There appeared no way to get a spacecraft to slow down enough to glide into Mars’ gravitational spacetime depression because the “bowl,” not that deep to begin with, was itself a too-rapidly moving target. “I gave up on it,” Belbruno says.
However, while recently consulting for the Boeing Corp., the major contractor for NASA’s Space Launch System, which is intended to take humankind to Mars, Belbruno, Topputo and colleagues stumbled on an idea: Why not go with the flow near Mars? Sailing a spacecraft into an orbital path anywhere from a million to even tens of millions of kilometers ahead of the Red Planet would make it possible for Mars (and its spacetime bowl) to ease into the spacecraft’s vicinity, thus subsequently letting the spacecraft be ballistically captured. Boeing, intrigued by this novel avenue to Mars, funded the study, in which the authors crunched some numbers and developed models for the capture.
Expanding our Martian horizons
Ballistic capture is not the only fuel-saving technique for entering orbit. In another approach, called aerocapture, an arriving spacecraft dives into the Martian atmosphere and lets friction eat away at some of its excess velocity, rather than relying solely on a big fuel burn to do the trick. That method, however, requires a heavy heat shield, which adds extra mass and thus costs to liftoff, offsetting the penny-pinching on fuel for a Hohmann transfer burn on arrival. Ballistic capture, Topputo says, is “slower and gentler.”
Ballistic capture therefore offers many advantages over current approaches for heading to Mars. Beyond avoiding the fuel-guzzling of a Hohmann transfer, for instance, it reduces danger to the craft because the vessel no longer must decelerate on a dime in a tight window near Mars, risking over- or undershooting its mark. The approach also drops fuel needs for the overall journey by 25 percent, Belbruno says, in a rough estimate. That reduction could be used to save money but it could also, instead, allow for bigger payloads at comparable prices. Delivering more mass to Martian orbit can then mean getting more robotic rovers, supplies or what have you to the surface. “What we want to do is leverage [ballistic capture] to put more mass on the ground,” Green says. “That’s the dream.”
Avoiding the need to send the rocket up during rare launch windows would also be a big deal because launch delays are notoriously frequent. Missing a window can mean grounding a Mars mission for two years, plus wasted launch prep costs.
For ‘bots, as well as bodies?
Ballistic capture does come with plenty of caveats, of course. A straight shot with abrupt braking at Mars takes about six months whereas a trip relying on ballistic capture would take an additional several months. The burn-free, capture altitude is also quite high—some 20,000 kilometers above Mars, far beyond where science satellites set up shop to scrutinize the planet up close. But taking along just a little extra fuel can then gently lower a ballistically captured spacecraft into scientifically valuable, standard orbits of around 100 to 200 kilometers like those achieved with Hohmann transfers—or even onward to the Martian surface for a landing.
For manned missions, ballistic transfer would be a mixed blessing. On one hand, its longer journeys would add to the challenges of ferrying people to Mars. We’re already worried about Mars-bound explorers driving each other crazy stuck in a tin can for six months, not to mention soaking up unacceptably high space radiation doses. For that reason, robotic missions look to be the first potential beneficiaries of Belbruno and Topputo’s new low-energy transfers.
On the other hand, because the need for launch windows would go away, ballistic capture could maintain a steady stream of supplies to the planet. Any extended Mars habitation effort would probably depend on Earth for materiel, at least until the establishment of self-sufficient farming and manufacturing. “Ballistic capture would be a good way to send supplies to Mars in advance of a manned mission,” Belbruno says, “or as part of one.”
NASA’s Green agrees. “This [ballistic capture technique] could not only apply here to the robotic end of it but also the human exploration end,” he says. Accordingly, Green arranged for Belbruno to speak with the agency’s Johnson Space Center staff back in October about how manned missions might exploit the concept.
Even further down the road, ballistic capture would be perfect, Belbruno says, for placing satellites into “areostationary” orbits—the same as geostationary, except at Mars (aka Ares). The upshot: Martian Internet and cell phone networks, anyone? If the new low-energy transfer works at Mars, it could, in theory, also be extended to deliver matter in bulk to any world in the solar system.
This potential breakthrough research is admittedly still in an early, theoretical phase. Ongoing work includes reworking the calculations of the physics by factoring in smaller influences on a Mars-bound spacecraft than the pull of gravity from Mars itself, such as Jupiter’s gravitational pull. NASA’s Green said he envisions the agency wanting to test ballistic capture transfers at Mars in the 2020s.
Belbruno has his fingers crossed. “The route to the moon I found in 1991 was thought to be perhaps the only application of my theory,” he says. “I am very excited about this Mars result.”
We have plenty of disagreement about the ITN and tempers are clearly getting frayed, which is never a good thing. So how about this: Let me see if I can get Ed Belbruno to do a piece for Centauri Dreams on these ideas and engage him in the discussion. I checked in with him last week and he was traveling, but let me see what might be possible. Dealing with the source seems the best way forward.
Here is the paper by Belbruno & Toppotu: http://arxiv.org/pdf/1410.8856v1.pdf
On page 15 is a chart showing aphelion burns. The are all a little more than 2 km/s.
If the burn is done at a 300 km altitude periaerion, .7 km/s suffices for Mars Capture.
Ballistic Mars capture is more expensive by 1.3 km/s.
Regarding Hiten, an apogee of ~300,000 km had already been attained. From LEO, this apogee takes about 3.1 km/s to achieve.
The Farquhar route from LEO to EML2 takes 3.5 km/s. If a temporary orbit in the Moon’s upper Hill Sphere is the goal, ballistic lunar capture only saves .4 km/s.
@J. Jason Wentworth October 8, 2015 at 1:56
‘By using lunar space elevators originating from the Moon’s polar regions (the elevators could be made of existing high-strength fibers such as Kevlar or Spectra, and they would curve down [or up] to the Moon’s equatorial plane)…’
The cables can be draped over the poles from ML1 to ML2 and over any where on the Earth facing terminator as well as to anywhere on the surface of the moon. It would be better to use a tube and then gases including water vapour can be moved up or down with little or no energy required and it would even allow the weight of the tube to be supported by the up pressure allowing a much larger load on the outside of the tube.
‘..and other ice-derived commodities (ammonia, methane, etc.) from cometary or asteroidal ice that had been stored in shadowed lunar craters earlier (or that had been made from the “native” lunar polar ice).’
http://www.americaspace.com/?p=60048
Interesting is the amount of organics from which we can make plastics.
This is an interesting article on how it all started,
https://medium.com/@jbenson/interplanetary-superhighway-8e3e734346ed
@Paul
‘Let me see if I can get Ed Belbruno to do a piece for Centauri Dreams on these ideas and engage him in the discussion. I checked in with him last week and he was traveling, but let me see what might be possible. Dealing with the source seems the best way forward.’
Thanks Paul
All of us look forward to any discussions.
From the article Charley linked to:
“What’s more, the trajectory Belbruno had designed used a fraction of the fuel that a direct launch to the Moon would use, a trajectory called the Hohmann transfer.”
Wrong.
Hiten had already invested 3.1 km/s to get a high apogee.
Farquhar’s route is basically a Hohmann path to the moon with a lunar capture burn at perilune and a parking burn at an EML2 apolune. His route from LEO to EML2 totals 3.5 km/s.
Let’s see, 3.1/3.5 = .886. Well, technically 88.6% could be called a fraction. But that’s not the connotation I’m picking up from Benson’s account.
Sorry Michael and Charley. I should have written “the article Michael had linked to”.
Sorry to interject this again, but did anyone read my comments concerning the impact of the long time trajectories to various celestial bodies and their impact on human travelers ? Did anybody comment to that particular observation that I made?
Charlie, I’ll throw this in: If we found long-haul trajectories that could save fuel, etc. but took a great deal of time, they would doubtless be used not for human missions but for things like robotic re-supply. To a colony on Mars, for example.