November 2005 Newsletter

Stockton Astronomical Society

Valley Skies

Valley Skies - November 2005 Issue

Editor's Corner...

A most interesting evening...

Many thanks to Dr. Theresa McRae, Chair of the Science and Mathematics Division at Delta College for arranging the tour of the Microscopy Center for our October 13 SAS meeting.

About 35 people turned out for this special program. Following our usual brief session of introductions and announcements in the planetarium, Dr. McRae took the opportunity to fill us in on the latest prospects for the future of the Clever Planetarium.

A recent report in The Record had indicated that the Cunningham building - of which the planetarium is a part - is slated for demolition as part of the plans for campus redevelopment. However, Theresa pointed out that the infrastructure (plumbing and wiring, heating and a/c) of the planetarium is isolated from the rest of Cunningham, so the rest of the building could be razed and the planetarium preserved. She is very optimistic that that will be the case.

Theresa also reported that a study is under way to completely revamp the planetarium: retaining the Spitz projector but updating the controls, including a completely new console; replacing the existing seating; and adding a full-dome digital projection system.

If all this can be accomplished, it will give the Clever Planetarium a whole new lease on life as a community resource, providing the capability for state-of-the-art educational and entertainment programs for both school field trips and public shows. Hold a good thought for a positive outcome.

Dr. McRae took us through a twenty-minute PowerPoint presentation about nanotechnology, then led us across campus to the Microscopy Center. Our group of about 35 was split into three for a 45 minute tour of the Center.

Many thanks to Lab Manager Cathy Davis and students Edward Lewis and Ken Dunbar who generously gave their evening to be our guides through this most impressive facility.

* * *

Many of us have been building and using Dobsonian telescopes for years without ever meeting the man behind the concept. John Dobson revolutionized amateur astronomy several decades ago with the simple-to-build and simple-to-use telescope design that bears his name. John will make a personal appearance on November 19 at the Eastbay premiere showing of "A Sidewalk Astronomer" in the 700-seat El Campanil Theater in Antioch. (See page 8 of the newsletter for details.)

Thank you to Marshal Merriam for forwarding the information about this program. As Marshal points out, there won't be many more opportunities to meet with John Dobson.

...Trevor Atkinson

The Science Directorate at NASA's Marshall Space Flight Center sponsors the Science@NASA web sites. The mission of Science@NASA is to help the public understand how exciting NASA research is and to help NASA scientists fulfill their outreach responsibilities.

Building a Better Rocket Engine

by Patrick L. Barry

Engineers have found a way to boost the performance of liquid fueled rockets. Their secret: innovative plumbing.

October 14, 2005: When you think of future rocket technology, you probably think of ion propulsion, antimatter engines and other exotic concepts.

Not so fast! The final chapter in traditional liquid-fueled rockets has yet to be written. Research is underway into a new generation of liquid-fueled rocket designs that could double performance over today's designs while also improving reliability.

Robert Goddard and a 1920s-vintage liquid-fueled rocket.

Liquid-fueled rockets have been around for a long time: The first liquid-powered launch was performed in 1926 by Robert H. Goddard. That simple rocket produced roughly 20 pounds of thrust, enough to carry it about 40 feet into the air. Since then, designs have become sophisticated and powerful. The space shuttle's three liquid-fueled onboard engines, for instance, can exert more than 1.5 million pounds of combined thrust en route to Earth orbit.

You might assume that, by now, every conceivable refinement in liquid-fueled rocket designs must have been made. You'd be wrong. It turns out there's room for improvement.

Led by the US Air Force, a group consisting of NASA, the Department of Defense, and several industry partners are working on better engine designs. Their program is called Integrated High Payoff Rocket Propulsion Technologies, and they are looking at many possible improvements. One of the most promising so far is a new scheme for fuel flow: The basic idea behind a liquid-fueled rocket is rather simple. A fuel and an oxidizer, both in liquid form, are fed into a combustion chamber and ignited. For example, the shuttle uses liquid hydrogen as its fuel and liquid oxygen as the oxidizer. The hot gases produced by the combustion escape rapidly through the cone-shaped nozzle, thus producing thrust.

The details, of course, are much more complicated. For one, both the liquid fuel and the oxidizer must be fed into the chamber very rapidly and under great pressure. The shuttle's main engines would drain a swimming pool full of fuel in only 25 seconds!

This gushing torrent of fuel is driven by a turbopump. To power the turbopump, a small amount of fuel is "preburned", thus generating hot gases that drive the turbopump, which in turn pumps the rest of the fuel into the main combustion chamber. A similar process is used to pump the oxidizer.

Today's liquid-fueled rockets send only a small amount of fuel and oxidizer through the preburners. The bulk flows directly to the main combustion chamber, skipping the preburners entirely.

One of many innovations being tested by the Air Force and NASA is to send all of the fuel and oxidizer through their respective preburners. Only a small amount is consumed there--just enough to run the turbos; the rest flows through to the combustion chamber.

A rendering of the Integrated Powerhead Demonstrator, showing its innovative plumbing for routing fuel and oxidizer to the combustion chamber.

This "full-flow staged cycle" design has an important advantage: with more mass passing through the turbine that drives the turbopump, the turbopump is driven harder, thus reaching higher pressures. Higher pressures equal greater performance from the rocket.

Such a design has never been used in a liquid-fueled rocket in the U.S. before, according to Gary Genge at NASA's Marshall Space Flight Center. Genge is the Deputy Project Manager for the Integrated Powerhead Demonstrator (IPD)--a test-engine for these concepts.

"These designs we're exploring could boost performance in many ways," says Genge. "We're hoping for better fuel efficiency, higher thrust-to-weight ratio, improved reliability--all at a lower cost."

"At this phase of the project, however, we're just trying to get this alternate flow pattern working correctly," he notes.

Already they've achieved one key goal: a cooler-running engine. "Turbopumps using traditional flow patterns can heat up to 1800 C," says Genge. That's a lot of thermal stress on the engine. The "full flow" turbopump is cooler, because with more mass running through it, lower temperatures can be used and still achieve good performance. "We've lowered the temperature by several hundred degrees," he says.

IPD is meant only as a testbed for new ideas, notes Genge. The demonstrator itself will never fly to space. But if the project is successful, some of IPD's improvements could find their way into the launch vehicles of the future.

Almost a hundred years and thousands of launches after Goddard, the best liquid-fueled rockets may be yet to come.

A Wrinkle in Space-Time

By Trudy E. Bell

When a massive star reaches the end of its life, it can explode into a supernova rivaling the brilliance of an entire galaxy. What's left of the star fades in weeks, but its outer layers expand through space as a turbulent cloud of gases. Astronomers see beautiful remnants from past supernovas all around the sky, one of the most famous being the Crab Nebula in Taurus.

When a star throws off nine-tenths of its mass in a supernova, however, it also throws off nine-tenths of its gravitational field.

Astronomers see the light from supernovas. Can they also somehow sense the sudden and dramatic change in the exploding star's gravitational field?

Yes, they believe they can. According to Einstein's general theory of relativity, changes in the star's gravitational field should propagate outward, just like light-indeed, at the speed of light.

Those propagating changes would be a gravitational wave.

Einstein said what we feel as a gravitational field arises from the fact that huge masses curve space and time. The more massive an object, the more it bends the three dimensions of space and the fourth dimension of time. And if a massive object's gravitational field changes suddenly-say, when a star explodes-it should kink or wrinkle the very geometry of space-time. Moreover, that wrinkle should propagate outward like ripples radiating outward in a pond from a thrown stone.

LISA's three spacecraft will be positioned at the corners of a triangle 5 million kilometers on a side and will be able to detect gravitational wave induced changes in their separation distance of as little as one billionth of a centimeter.

The frequency and timing of gravitational waves should reveal what's happening deep inside a supernova, in contrast to light, which is radiated from the surface. Thus, gravitational waves allow astronomers to peer inside the universe's most violent events-like doctors peer at patients' internal organs using CAT scans. The technique is not limited to supernovas: colliding neutron stars, black holes and other exotic objects may be revealed, too.

NASA and the European Space Agency are now building prototype equipment for the first space experiment to measure gravitational waves: the Laser Interferometer Space Antenna, or LISA.

LISA will look for patterns of compression and stretching in space-time that signal the passage of a gravitational wave. Three small spacecraft will fly in a triangular formation behind the Earth, each beaming a laser at the other two, continuously measuring their mutual separation. Although the three 'craft will be 5 million kilometers apart, they will monitor their separation to one billionth of a centimeter, smaller than an atom's diameter, which is the kind of precision needed to sense these elusive waves.

LISA is slated for launch around 2015.

To learn more about LISA, go to http://lisa.jpl.nasa.gov. Kids can learn about LISA and do a gravitational wave interactive crossword at http://spaceplace.nasa.gov/en/kids/lisaxword/lisaxword.shtml.

This article was provided by the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.

Opportunity Lost?

10-15-05: "I am writing about the Springfield telescope owned by Dr. Custer.

Photo from September 1986 issue of the San Joaquin Medical Society newsletter.

Recently I was talking with the curator of the Space Museum at the Smithsonian Institution. It turns out that he, and some of his colleagues, had admired Dr. Custer's account of the telescope, as well as the published photos of M31 in "Sky & Telescope."

As it happens, Dr. Custer's telescope is a historic instrument -- probably the finest Springfield used for photography.

In short, the Smithsonian would like to acquire it for exhibition!

It is very interesting, but that Springfield is actually fairly widely known in the (restricted) circle of lovers of astronomical instruments, and a number of people have wanted to know about its fate. I think it would be a real coup to have a Stockton instrument on display at our national museum of science!"

With best wishes, Rudi Paul Lindner -
Practice Limited to History - University of Michigan.

Dr. Custer's telescope was dismantled and removed from his back yard, at his request, about 10-12 years ago. We still have the mirror at the planetarium. Unfortunately, the Springfield mount was subsequently disassembled, and some parts were used in another telescope.