by Paul Gilster | Nov 25, 2005 | Advanced Rocketry
According to this note from Out of the Cradle, the site will feature live blog coverage on the Falcon-1 launch, now scheduled for Saturday. Falcon-1 is the first all new orbital rocket in over a decade, and the first privately developed liquid fuel rocket to attempt orbit. Keep an eye as well on the SpaceX site for further information. If the Falcon-1 makes orbit, it’s good news for space agency budgets everywhere — priced at $6.7 million, the SpaceX rocket offers the lowest cost to orbit of any launch vehicle in the world, a significant step forward for the commercial space industry.
by Paul Gilster | Nov 24, 2005 | Breakthrough Propulsion, Missions |
Consider two hypothetical spacecraft. The Orion vehicle would have worked by setting off low-yield nuclear devices behind a massive pusher plate, driving forward a payload attached at a safe distance from the pusher (and protected by mind-boggling shock absorbers). Even if we had the nuclear devices at our disposal, agreed to use them for such a purpose, and found the political will to construct an Orion craft for deep space exploration, a problem still remains: most of the energy from the nuclear blasts is dissipated into space, and the craft thus requires a huge critical mass of fission explosives.
Orion, in short, is not efficient in using its energies. Now consider Project Daedalus, the hypothetical mission to Barnard’s Star designed by members of the British Interplanetary Society back in the 1970s. Daedalus was designed to use fusion microexplosions instead of fission. One of the reasons the Daedalus craft demanded as much fuel as it did is that the ignition apparatus, whether laser or particle beam, to ignite fusion is massive, adding unwanted heft to the vehicle. Daedalus would have massed an overwhelming 54,000 tons.
But there is a third option, discussed by Friedwardt Winterberg (University of Nevada/Reno) in a new paper in Acta Astronautica. Winterberg describes so-called ‘mini-nukes,’ which are devices in which the mass of the fission explosive is hugely reduced by a reflector in which a deuterium-tritium (DT) fusion reaction takes place — the fusion neutrons thereby increase the fission rate, and the increased fission rate, in turn, increases the fusion production rate. The implosive compression to ignite the process is provided by chemical high explosives.
We wind up with a fission-fusion assembly with serious advantages: 1) we eliminate the weight of a laser or particle beam generator to ignite fusion, and 2) we add to the specific impulse and thrust of the exhaust, which is composed of combustion products both from the nuclear and chemical reactions.
And no longer do we, Orion-style, lose the bulk of our energies into space. “With mini-nukes,” Winterberg writes, “the situation is much better because the explosions can take place there in the focus of a parabolic reflector positioned in close proximity to the spacecraft. Since still smaller mini-nukes appear possible, with their feasibility depending only on the technical perfection to focus the chemical energy for ignition, the mini-nukes can be detonated inside a large combustion chamber…”
The paper is Winterberg, F., “Mini-fission-fusion explosive devices (mini-nukes) for nuclear pulse propulsion,” Acta Astronautica Vol. 57 (2005), pp. 707-712. Some of Winterberg’s earlier work was studied, incidentally, by the Daedalus designers as they set about examining various ways of making an inertial confinement fusion system that could power their starprobe.
And incidentally, check this Fusion News Update at the Star Spangled Cosmos site for news of a possible development in inertial confinement fusion in South Korea.
by Paul Gilster | Nov 23, 2005 | Exoplanetary Science
If you’re going to have a conference on exoplanets, there is no better venue than l’Observatoire de Haute-Provence. It was here, just ten years ago, that Mayor and Queloz discovered the first planet orbiting a main sequence star outside our own Solar System. The star was 51 Pegasi, a name that will surely be recalled for generations as the first confirmation that planets exist around other stars. And attendees at a late August conference celebrating the discovery had much to say about the course of future exoplanetary developments.
David Charbonneau (Harvard-Smithsonian Center for Astrophysics) summarizes the conference findings in his paper “Hot Jupiters: Lands of Plenty,” now available on the arXiv site. A major issue stands out: the huge leap in precision for radial velocity observations of the sort that bagged 51 Pegasi’s planet, allowing researchers to monitor a wider group of stars than the F, G, K and early M-class dwarfs that have been the focus heretofore. The new precision is energizing more finely targeted searches for planets around low-mass stars, young stars, evolved stars and binary systems, among other investigations.
We’re not yet up to the kind of Doppler precision that would allow detection of a terrestrial world in the habitable zone of a low-mass star, but Charbonneau says that data presented at the conference hints that still further improvements are close. Another major player in sharpening our exoplanetary focus: the role of space-based observatories like Spitzer and Hubble, the latter of which has been spectacularly effective in the study of planetary transits.
Charbonneau also reports on a poll he conducted at the conference. The paper breaks down the answers, two of which catch the eye:
Most participants believe that we’ll have detected 1000 exoplanets within ten years;
The majority of attendees believe extraterrestrial life will be detected before 2050, but a significant number believe it will only be detected later than that or not at all.
Centauri Dreams‘ take: Charbonneau’s final thought mirrors my own: “With the exciting discoveries of the previous decade as our guide, we can only assume that the prevailing wisdom will, once again, be proven wholly unjustified.” Which is probably the surest thing to be said about a survey of practitioners in a field this mutable– remember that ten years ago, the very idea of a ‘hot Jupiter’ seemed too fanciful for words. Exoplanetary detections continue to challenge everything we know about planet formation, and as the conference also made clear, we have nothing but guesswork to supply about the incidence of terrestrial worlds around other stars. It is, in short, an absolutely extraordinary time to be alive and practicing science.
by Paul Gilster | Nov 22, 2005 | Deep Sky Astronomy & Telescopes
Hubble’s recent findings about ‘Einstein rings’ remind us of the value of using gravitational lensing to observe distant objects. When light from a distant galaxy is bent by an intervening galaxy, the effect can be to create multiple separate images of the more distant source. But line up the two galaxies exactly and the gravitational bending causes the intriguing phenomenon called an Einstein ring, which is something like the pattern of a bull’s eye around the foreground galaxy.
Einstein rings are useful objects to astronomers, as witness this news release from the Harvard-Smithsonian Center for Astrophysics:
“An Einstein ring is one of the most dramatic demonstrations of the general theory of relativity in the cosmos,” said Adam Bolton of the Harvard-Smithsonian Center for Astrophysics (CfA). “It provides an unique opportunity to study the most massive galaxies in the universe.”
Interesting, too, from a mission point of view, for as Centauri Dreams continues to opine, a mission to the Sun’s gravity focus some 550 AU out would be a logical first step as we push into targeted interstellar missions. Such a mission, usually discussed under the FOCAL designation championed by Italian physicist Claudio Maccone, would provide unparalleled opportunities for astronomical observation and SETI research, and the chance to develop and fine-tune technologies ranging from solar sail to nuclear-electric propulsion.
Image: The thin blue bull’s-eye patterns in these six Hubble Space Telescope images are so-called “Einstein rings,” which are the most elegant manifestation of gravitational lensing. The yellowish-red blobs are giant elliptical galaxies roughly 2 to 4 billion light-years away. Einstein rings are created as the light from galaxies twice as far away is distorted into circular shapes by the gravity of the intervening giant elliptical galaxies. Gravitational lensing allows astronomers to study the distribution of unseen matter in the lensing galaxies, and to observe light from more distant galaxies that would otherwise remain undetectably faint. Credit: NASA / ESA / A. Bolton (CfA) / and the SLACS Team
But back to Hubble, and the combination of its assets with those of the Sloan Digital Sky Survey (SDSS). Astronomers have used data from the two to identify 19 new gravitational lens galaxies, bringing the known number of such lenses well above 100. Of the 19, eight involve Einstein rings. All this is part of the Sloan Lens ACS Survey, which draws its candidate objects from SDSS and then uses Hubble’s Advanced Camera for Surveys for closer scrutiny.
An Einstein ring can help astronomers estimate the mass of the intervening galaxies and can also be a source of good information about the distribution of dark matter in elliptical galaxies. This is potent stuff: dark matter seems to make up the bulk of the total mass of the universe, and plays a huge role in the formation of the familar galactic shapes we know from visible light photographs. From the release, quoting Leon Koopmans of the Kapteyn Astronomical Institute in the Netherlands:
“Being able to study these and other gravitational lenses as far back in time as several billions years allows us to directly see whether the distribution of dark and visible mass changes with cosmic time,” said Koopmans. “With this information, we can test the commonly held idea that galaxies form from collision and mergers of smaller galaxies.”
Initial survey findings are to appear in early 2006 in The Astrophysical Journal. You can see a preprint of the paper “The Sloan Lens ACS Survey. I. A Large Spectroscopically Selected Sample of Massive Early-Type Lens Galaxies” here.
by Paul Gilster | Nov 21, 2005 | Advanced Rocketry, Missions |
The Japanese Hayabusa spacecraft has always seemed to have a couple of strikes against it, at least in terms of media coverage. Never much in the spotlight, the ambitious attempt to explore and bring back samples from the asteroid Itokawa has been all but eclipsed by China’s recent manned orbital ventures. And Centauri Dreams suspects that’s a primary problem: robotic missions don’t draw the public eye the way risky manned flights do, even if the scientific payback from the former is often immeasurably greater.
Now Hayabusa is encountering a different set of problems. The Minerva robot was to have landed on Itokawa last week, but disappeared after its release. A lower profile issue has been solar flare damage to the spacecraft’s solar panels and continuing problems with its positioning control system. And now we have word of a mission-endangering glitch: Hayabusa failed to touch down on the tiny asteroid when the attempt was made on Sunday. “I don’t think it landed,” project leader Junichiro Kawaguchi told a news conference, although it’s clear Hayabusa came close.
Image: Hayabusa casts a shadow of its own, dramatically backlit by the Sun. Credit: JAXA.
A second attempt will be made this Friday and is vital to the mission’s success, as the reason for landing was to fire a metal pellet into the surface to collect material from the asteroid for return to Earth. Let us hope the Friday attempt goes well, for this is a remarkable, pioneering mission. Centauri Dreams celebrates the Japan Aerospace Exploration Agency’s work on ion thrusters, those highly fuel-efficient, low thrust engines so suited to deep space exploration. The Hayabusa engines use microwave-ionized xenon gas pushed through a strong magnetic field to propel the craft. As they did with Deep Space 1, the thrusters aboard Hayabusa provided outstanding service. And let us hope that enough data can be reconstructed from the Minerva attempt to teach us valuable lessons on robotics to go along with Hayabusa’s already impressive achievements in autonomous navigation.
Perhaps a sucess on Friday will get Hayabusa into the media spotlight. Until then, Centauri Dreams tends to agree with these remarks on the Pausanias weblog:
The Japanese Hayabusa probe, ignored by the world media, is using ion power to travel to an earth-crrossing asteroid, dance around it, and in the next few days, to touch down on its surface, leave a surface probe, blast off some regolith, and then return it to the Australian desert. This should be awesome stuff for a public that lined up around the block to see Armageddon and Deep Impact. But ‘nary a peep, and only a one-page garbled write-up in Aviation Week. Maybe instead of using government employees for publicity, JAXA/NASA/ESA/RAKA could get together and hire some Hollywood producers to handle their public relations (Spielberg, Hanks, Lucas should fund it for free, considering their debt to the space program for making the public ready to accept sci-fi cinema). Short public service films in theatres or on cable channels between the programs with the latest utterly awesome pix from around the solar system might go a lot farther than lame press conferences…
For background information and updates, the Hayabusa home page is here.
