Four space shuttle veterans were inducted into the Astronaut Hall of Fame at Florida’s Kennedy Space Center Visitor Complex on Saturday. The newest entrants were Daniel Brandenstein, Robert Gibson, Story Musgrave and Sally Ride (the first American woman in space). The event drew hundreds of people – many were tourists – and actor Lance Henriksen (“The Right Stuff” and “Aliens”) presided over the event. They join 48 astronauts already enshrined at the hall.
Image credit: NASA
NASA announced today that it has awarded an $825 million contract to aerospace firm TRW to build the replacement for the Hubble Space Telescope: The James Webb Space Telescope. Named for NASA’s second administrator, this new observatory will launch in 2010 and operate 1.5 million km away from the Earth (Hubble is in low-Earth orbit). If all goes as planned, the observatory’s 6 metre mirror will offer a tremendous leap in resolution over Hubble.
NASA today selected TRW, Redondo Beach, Calif., to build a next-generation successor to the Hubble Space Telescope in honor of the man who led NASA in the early days of the fledgling aerospace agency.
The space-based observatory will be known as the James Webb Space Telescope, named after James E. Webb, NASA’s second administrator. While Webb is best known for leading Apollo and a series of lunar exploration programs that landed the first humans on the Moon, he also initiated a vigorous space science program, responsible for more than 75 launches during his tenure, including America’s first interplanetary explorers.
“It is fitting that Hubble’s successor be named in honor of James Webb. Thanks to his efforts, we got our first glimpses at the dramatic landscapes of outer space,” said NASA Administrator Sean O’Keefe. “He took our nation on its first voyages of exploration, turning our imagination into reality. Indeed, he laid the foundations at NASA for one of the most successful periods of astronomical discovery. As a result, we’re rewriting the textbooks today with the help of the Hubble Space Telescope, the Chandra X-ray Observatory and, in 2010, the James Webb Telescope.”
The James Webb Space Telescope is scheduled for launch in 2010 aboard an expendable launch vehicle. It will take about three months for the spacecraft to reach its destination, an orbit 940,000 miles or 1.5 million kilometers in space, called the second Lagrange Point or L2, where the spacecraft is balanced between the gravity of the Sun and the Earth.
Unlike Hubble, space shuttle astronauts will not service the James Webb Space Telescope because it will be too far away.
The most important advantage of this L2 orbit is that a single-sided sun shield on only one side of the observatory can protect Webb from the light and heat of both the Sun and Earth. As a result, the observatory can be cooled to very low temperatures without the use of complicated refrigeration equipment. These low temperatures are required to prevent the Webb’s own heat radiation from exceeding the brightness of the distant cool astronomical objects.
Before and during launch, the mirror will be folded up. Once the telescope is placed in its orbit, ground controllers will send a message telling the telescope to unfold its high-tech mirror petals.
To see into the depths of space, the James Webb Space Telescope is currently planned to carry instruments that are sensitive to the infrared wavelengths of the electromagnetic spectrum. The new telescope will carry a near-infrared camera, a multi-object spectrometer and a mid-infrared
The James Webb Space Telescope will be able to look deeper into the universe than Hubble because of the increased light- collecting power of its larger mirror and the extraordinary sensitivity of its instruments to infrared light. Webb’s primary mirror will be at least 20 feet in diameter, providing much more light gathering capability than Hubble’s eight-foot primary mirror.
The telescope’s infrared capabilities are required to help astronomers understand how galaxies first emerged out of the darkness that followed the rapid expansion and cooling of the universe just a few hundred million years after the big bang. The light from the youngest galaxies is seen in the infrared due to the universe’s expansion.
Looking closer to home, the James Webb Space Telescope will probe the formation of planets in disks around young stars, and study supermassive black holes in other galaxies.
Under the terms of the contract valued at $824.8 million, TRW will design and fabricate the observatory’s primary mirror and spacecraft. TRW also will be responsible for integrating the science instrument module into the spacecraft as well as performing the pre-flight testing and on-orbit checkout of the observatory.
The Goddard Space Flight Center, Greenbelt, Md., manages the James Webb Space Telescope for the Office of Space Science at NASA Headquarters in Washington. The program has a number of industry, academic and government partners, as well as the European Space Agency and the Canadian Space Agency.
Original Source: NASA News Release
Image credit: NASA
As everybody knows, chemical rockets are too slow for space exploration. So, to speed up voyages around our Solar System, NASA is working on some new kinds of propulsion: ion engines, solar and plasma sails. Perhaps the most efficient will be hybrid systems, with different kinds of propulsion used at different points of a journey. This article gives you a breakdown of the technologies NASA’s currently working on.
“Mom, are we there yet?”
Every parent has heard that cry from the back seat of the car. It usually begins about 15 minutes after the start of any family trip. Good thing we rarely travel more than a few hundred or a few thousand miles from home.
But what if you were traveling to, say, Mars? Even at its closest approach to Earth every couple years, the red planet is always at least 35 million miles away. Six months there and six months back–at best.
“Houston, are we there yet?”
“Chemical rockets are just too slow,” laments Les Johnson, manager for in-space transportation technologies at NASA’s Marshall Space Flight Center. “They burn all their propellant at the beginning of a flight and then the spacecraft just coasts the rest of the way.” Although spacecraft can be sped up by gravity assist–a celestial crack-the-whip around planets, such as the one around Saturn that flung Voyager 1 to the edge of the solar system–round-trip travel times between planets are still measured in years to decades. And a journey to the nearest star would take centuries if not millennia.
Worse yet, chemical rockets are just too fuel-inefficient. Think of driving in a gas guzzler across a country with no gas stations. You’d have to carry boatloads of gas and not much else. In space missions, what you can carry on your trip that isn’t fuel (or tanks for fuel) is called the payload mass–e.g., people, sensors, samplers, communications gear and food. Just as gas mileage is a useful figure of merit for the fuel efficiency of a car, the “payload mass fraction”–the ratio of a mission’s payload mass to its total mass–is a useful figure of merit for the efficiency of propulsion systems.
With today’s chemical rockets, payload mass fraction is low. “Even using a minimum-energy trajectory to send a six-person crew from Earth to Mars, with chemical rockets alone the total launch mass would top 1,000 metric tons–of which some 90 percent would be fuel,” said Bret G. Drake, manager for space launch analysis and integration at Johnson Space Center. The fuel alone would weigh twice as much as the completed International Space Station.
A single Mars expedition with today’s chemical propulsion technology would require dozens of launches–most of which most would simply be launching chemical fuel. It’s as if your 1-ton compact car needed 9 tons of gasoline to drive from New York City to San Francisco because it averaged only a mile per gallon.
In other words, low-performance propulsion systems is one major reason why humans have not yet set foot on Mars.
More efficient propulsion systems increase the payload mass fraction by giving better “gas mileage” in space. Since you don’t need as much propellant, you can carry more stuff, go in a smaller vehicle, and/or get there faster and cheaper. “The key message is: we need advanced propulsion technologies to enable a low-cost mission to Mars,” Drake declared.
Thus, NASA is now developing ion drives, solar sails, and other exotic propulsion technologies that for decades have whooshed humans to other planets and stars–but only in the pages of science fiction.
From tortoise to hare
What are the science-fact options?
NASA is hard at work on two basic approaches. The first is to develop radically new rockets that have an order-of-magnitude better fuel economy than chemical propulsion. The second is to develop “propellant-free” systems that are powered by resources abundant in the vacuum of deep space.
All these technologies share one key characteristic: they start slowly, like the proverbial tortoise, but over time turn into a hare that actually wins a race to Mars–or wherever. They rely on the fact that a small continuous acceleration over months can ultimately propel a spacecraft far faster than one enormous initial kick followed by a long period of coasting.
Above: This low-thrust spaceship (an artist’s concept) is propelled by an ion engine and powered by solar electricity. Eventually the craft will pick up speed–a result of relentless acceleration–and race along at many miles per second. Image credit: John Frassanito & Associates, Inc.
Technically speaking, they’re all systems with low thrust (meaning you would barely feel the oh-so-gentle acceleration, equivalent to that of the weight of a piece of paper lying on your palm) but long operating times. After months of continuing small acceleration, you’d be clipping along at many miles per second! In contrast, chemical propulsion systems are high thrust and short operating times. You’re crushed back into the seat cushions while the engines are firing, but only briefly. After that the tank is empty.
“A rocket is anything that throws something overboard to propel itself forward,” Johnson pointed out. (Don’t believe that definition? Sit on a skateboard with a high-pressure hose pointed one way, and you will be propelled in the opposite way).
Leading candidates for the advanced rocket are variants of ion engines. In current ion engines, the propellant is a colorless, tasteless, odorless inert gas, such as xenon. The gas fills a magnet-ringed chamber through which runs an electron beam. The electrons strike the gaseous atoms, knocking away an outer electron and turning neutral atoms into positively-charged ions. Electrified grids with many holes (15,000 in today’s versions) focus the ions toward the spaceship’s exhaust. The ions shoot past the grids at speeds of up to more than 100,000 miles per hour (compare that to an Indianapolis 500 racecar at 225 mph)–accelerating out the engine into space, so producing thrust.
Where does the electricity come from to ionize the gas and charge the engine? Either from solar panels (so-called solar electric propulsion) or from fission or fusion (so-called nuclear electric propulsion). Solar electric propulsion engines would be most effective for robotic missions between the sun and Mars, and nuclear electric propulsion for robotic missions beyond Mars where sunlight is weak or for human missions where speed is of the essence.
Ion drives work. They’ve proven their mettle not only in tests on Earth, but in working spacecraft–the best-known being Deep Space 1, a small technology-testing mission powered by solar electric propulsion that flew by and took pictures of Comet Borrelly in September, 2001. Ion drives like the one that propelled Deep Space 1 are about 10 times as efficient as chemical rockets.
The lowest-mass propulsion systems, however, may be those that carry no on-board propellant at all. In fact, they’re not even rockets. Instead, in true pioneer style, they “live off the land”–relying for energy on natural resources abundant in space, much as pioneers of yore relied for food on trapping animals and finding roots and berries on the frontier.
The two leading candidates are solar sails and plasma sails. Although the effect is similar, the operating mechanisms are very different.
A solar sail consists of an enormous area of gossamer, highly reflective material that is unfurled in deep space to capture light from the sun (or from a microwave or laser beam from Earth). For very ambitious missions, sails could range up to many square kilometers in area.
Solar sails take advantage of the fact that solar photons, although having no mass, do have momentum–several micronewtons (about the weight of a coin) per square meter at the distance of Earth. This gentle radiation pressure will slowly but surely accelerate the sail and its payload away from the sun, reaching speeds of up to 150,000 miles per hour, or more than 40 miles per second.
A common misconception is that solar sails catch the solar wind, a stream of energetic electrons and protons that boil away from the Sun’s outer atmosphere. Not so. Solar sails get their momentum from sunlight itself. It is possible, however, to tap the momentum of the solar wind using so-called “plasma sails.”
Plasma sails are modeled on Earth’s own magnetic field. Powerful on-board electromagnets would surround a spacecraft with a magnetic bubble 15 or 20 kilometers across. High-speed charged particles in the solar wind would push the magnetic bubble, just as they do Earth’s magnetic field. Earth doesn’t move when it’s pushed in this way–our planet is too massive. But a spacecraft would be gradually shoved away from the Sun. (An added bonus: just as Earth’s magnetic field shields our planet from solar explosions and radiation storms, so would a magnetic plasma sail protect the occupants of a spacecraft.)
Above: An artist’s concept of a space probe inside a magnetic bubble (or “plasma sail”). Charged particles in the solar wind hit the bubble, apply pressure, and propel the spacecraft. [more]
Of course, the original, tried-and-true propellant-free technology is gravity assist. When a spacecraft swings by a planet, it can steal some of the planet’s orbital momentum. This hardly makes a difference to a massive planet, but it can impressively boost the velocity of a spacecraft. For example, when Galileo swung by Earth in 1990, the speed of the spacecraft increased by 11,620 mph; meanwhile Earth slowed down in its orbit by an amount less than 5 billionths of an inch per year. Such gravity assists are valuable in supplementing any form of propulsion system.
Okay, now that you’ve zipping through interplanetary space, how do you slow down at your destination enough to go into a parking orbit and prepare for landing? With chemical propulsion, the usual technique is to fire retrorockets–once again, requiring large masses of onboard fuel.
A far more economical option is promised by aerocapture–braking the spacecraft by friction with the destination planet’s own atmosphere. The trick, of course, is not to let a high-speed interplanetary spacecraft burn up. But NASA scientists feel that, with an appropriately designed heat shield, it would be possible for many missions to be captured into orbit around a destination planet with just one pass through its upper atmosphere.
“No single propulsion technology will do everything for everybody,” Johnson cautioned. Indeed, solar sails and plasma sails would likely be useful primarily for propelling cargo rather than humans from Earth to Mars, because “it takes too long for those technologies to get up to escape velocity,” Drake added.
Nonetheless, a hybrid of several technologies could prove to be very economical indeed in getting a manned mission to Mars. In fact, a combination of chemical propulsion, ion propulsion, and aerocapture could reduce the launch mass of a 6-person Mars mission to below 450 metric tons (requiring only six launches)–less than half that attainable with chemical propulsion alone.
Such a hybrid mission might go like this: Chemical rockets, as usual, would get the spacecraft off the ground. Once in low-Earth orbit, ion drive modules would ignite, or ground controllers might deploy a solar or plasma sail. For 6 to 12 months, the spaceship–temporarily unmanned to avoid exposing the crew to large doses of radiation in Earth’s Van Allen radiation belts–would spiral away, gradually accelerating up to a final high Earth-departure orbit. The crew would then be ferried out to the Mars vehicle in a high-speed taxi; a small chemical stage would then kick the vehicle up to escape velocity, and it would head onward to Mars.
As Earth and Mars revolve in their respective orbits, the relative geometry between the two planets is constantly changing. Although launch opportunities to Mars occur every 26 months, the optimal alignments for the cheapest, fastest possible trips happen every 15 years–the next one coming in 2018.
Perhaps by then we’ll have a different answer to the question, “Houston, are we there yet?”
Original Source: NASA Science Story
Image credit: NASA
NASA has selected two new concepts to advance the search for extrasolar planets; one of the technologies will eventually be selected for the Terrestrial Planet Finder mission. The first choice involves the use of an Infrared Interferometer, where multiple spacecraft will simulate a much larger observatory and search for the infrared signature of a planet around a distant star. The other concept is a Visible Light Coronagraph; a telescope 4 times as large and 10 times as powerful as Hubble, capable of imaging distant planets directly. NASA will choose one path in 2005-2006.
As part of its quest to find Earth-sized planets around stars and look for telltale chemical signatures of life, NASA has chosen two mission architecture concepts for further study and technology development.
The two architectures are being explored for the Terrestrial Planet Finder mission. Each would use a different means to achieve the same goal ? to block the light from a parent star in order to see its much smaller, dimmer planets. That technology challenge has been likened to finding a firefly near the beam of a brilliant searchlight from far away. Additional goals of the mission would include characterizing the surfaces and atmospheres of newfound planets, and looking for the chemical signatures of life.
The two candidate architectures are:
— Infrared Interferometer: Multiple small telescopes on a fixed structure or on separated spacecraft flying in precision formation would simulate a much larger, very powerful telescope. The interferometer would utilize a technique called nulling to reduce the starlight by a factor of one million, thus enabling the detection of the very dim infrared emission from the planets.
— Visible Light Coronagraph: A large optical telescope, with a mirror three to four times bigger and at least 10 times more precise than the Hubble Space Telescope, would collect starlight and the very dim reflected light from the planets. The telescope would have special optics to reduce the starlight by a factor of one billion, thus enabling astronomers to detect the faint planets.
The Terrestrial Planet Finder project at NASA?s Jet Propulsion Laboratory, Pasadena, Calif., selected the two candidates based on results from four industrial-academic teams that conducted a 2-1/2 year study of more than 60 possible designs. The two architectures were determined to be sufficiently realistic to warrant further study and technological development in support of a launch of Terrestrial Planet Finder by the middle of the next decade.
NASA and JPL will issue calls for proposals seeking input on the development and demonstration of technologies to implement the two architectures, and on scientific research relevant to planet finding. It is anticipated that one of the two architectures will be selected in 2005 or 2006 to be implemented for the mission, which may include international collaboration.
Terrestrial Planet Finder is part of NASA?s Origins Program, a series of missions to study the formation of galaxies, stars and planets, and to search for life. The program seeks to answers the questions: Where did we come from? Are we alone?
More information on the Terrestrial Planet Finder is available at http://tpf.jpl.nasa.gov/ .
More information on the Origins Program is available at http://origins.jpl.nasa.gov . Additional information on JPL?s planet-finding missions is available at http://planetquest.jpl.nasa.gov/ .
JPL manages the Terrestrial Planet Finder mission and the Origins Program for NASA’s Office of Space Science, Washington, D.C. JPL is a division of the California Institute of Technology in Pasadena.
Original Source: NASA News Release
Image credit: Boeing
NASA believes it’s one step closer to replacing the aging space shuttle fleet. After analyzing hundreds of potential vehicle concepts, the Space Launch Initiative (SLI) has short listed the potential suppliers down to three teams: Boeing, Lockheed Martin, and Orbital Sciences/Northrop Grumman. Each team has provided several ideas that fulfill the requirements of the SLI: carry humans and satellites into orbit; carry government or commercial payloads; be operated by the private industry; and launch at a fraction of the cost of the space shuttle.
NASA is another step closer to defining the next-generation reusable space transportation system and successor to the Space Shuttle.
The Space Launch Initiative (SLI), a NASA-wide effort defining the future of human space flight, has completed its first milestone review ? resulting in a narrower field of potential candidates for the nation’s second-generation reusable space transportation system.
“To use the resources afforded by space, it’s critical to increase reliability and safety while at the same time reducing the cost of space transportation,” said Art Stephenson, director of NASA’s Marshall Space Flight Center, Huntsville, Ala., which manages the SLI for the Office of Aerospace Technology. “The Space Launch Initiative is doing the groundwork to accomplish these goals and create a second-generation launch system.”
“We’re not just designing a launch vehicle,” added Dennis Smith, also of Marshall, program manager of the Space Launch Initiative. “We’re designing the complete system.”
The recent review, called the Initial Architecture Technology Review, analyzed and evaluated competing second-generation reusable space transportation architectures and technologies against NASA and commercial mission requirements, as well as safety and cost goals.
Architecture refers to the complete transportation system design ? that is, the vehicles and their components that fly into space, as well as the ground operations needed for launch. The transportation system design includes an Earth-to-orbit reusable launch vehicle (the Space Shuttle is the first-generation reusable launch vehicle); on-orbit transfer vehicles and upper stages to put satellites into orbits; mission planning; ground and flight operations; and support infrastructure, both on orbit and on the ground.
Three contractor architecture teams ? The Boeing Company of Seal Beach, Calif.; Lockheed Martin Corp. of Denver; and a team including Orbital Sciences Corp. of Dulles, Va., and Northrop Grumman of El Segundo, Calif. ? presented dozens of potential architectures for review. Following the review, each retained a handful of possible candidates for the nation’s next-generation reusable space launch system.
The review allows the Space Launch Initiative to target investments and support what the program manager called the “up-front, homework part of the program” ? furthering technologies to aid in the development of a second-generation reusable launch vehicle. Another review will be held in November to further narrow potential space transportation architectures to two or three choices.
“We’re going to seek the final and best ideas from industry, academia and government,” said Smith. With the final selection of an architecture, full-scale development of a reusable launch vehicle could begin around the middle of this decade.
Since propulsion systems require a long lead-time to design, develop, test and evaluate, it isn’t surprising that propulsion analysis was a chief driver through the recently completed review activity.
“We spent a lot of time analyzing propulsion technologies,” said Smith. “Among the outcomes is a focus on kerosene-fueled main engines.” This focus is based on studies, conducted by the architecture contractors that examine performance of competing technologies in safety, reliability, cost and operability. Studies indicated that kerosene main engines have excellent potential to meet government and commercial needs. The second-generation vehicle will have a two-stage-to-orbit propulsion system based on engines fueled by all kerosene, all hydrogen or a combination of kerosene and hydrogen.
Dependable, long-life engines, along with crew escape and survival systems, and long-life, lightweight integrated airframes are among the Space Launch Initiative’s highest priorities. Each greatly impacts the program’s bottom line of increased safety, reliability and cost effectiveness.
Original Source: NASA News Release
Image credit: NASA
It was a bit of a rough ride, but Pathfinder arrived on the surface of Mars back in 1997 in perfect condition. It was the innovative (and unproven) airbag system that helped slow the lander’s descent, so NASA is planning to employ the system again for the 2003 Mars Exploration Rover missions. These rovers have a different mass than Pathfinder, so NASA engineers have gone back to the drawing board to figure out how to make airbags that inflate seconds before touchdown and can withstand an impact at freeway speeds.
Just one of the many problems in landing on another planet, after it’s been determined where to land and the method to get there, is landing safely. For JPL, a safe landing is “the name of the game,” as engineers work to prepare two rovers for the journey to Mars.
The Mars Exploration Rovers scheduled for launch in 2003 are using the same type airbag landing system that Mars Pathfinder used in 1997. The airbags must be strong enough to cushion the spacecraft if it lands on rocks or rough terrain and allow it to bounce across Mars’ surface at freeway speeds after landing. To add to the complexity, the airbags must be inflated seconds before touchdown and deflated once safely on the ground.
“The 2003 rovers have a different mass [than Sojourner, the Pathfinder rover], so we’ve made changes in the airbag design,” said John Carson, cognizant engineer. “Our requirement is to be able to land safely on a rock extending about a half-meter (about 18 inches) above the surface. Extensive testing gives us a process for trial and error before the final design.”
How to Build a Better Airbag
While most new automobiles now come with airbags, spacecraft don’t. The fabric being used for the new Mars airbags is a synthetic material called Vectran that was also used on Mars Pathfinder. Vectran has almost twice the strength of other synthetic materials, such as Kevlar, and performs better at cold temperatures.
Denier is a term that measures the diameter of the thread used in the product. There will be six 100-denier layers of the light but tough Vectran protecting one or two inner bladders of the same material in 200-denier, according to Dara Sabahi, mechanical systems architect. Using the 100-denier means there is more actual fabric in the outer layers where it is needed, because there are more threads in the weave.
Each rover uses four airbags with six lobes each, which are all connected. Connection is important, since it helps abate some of the landing forces by keeping the bag system flexible and responsive to ground pressure. The fabric of the airbags is not attached directly to the rover; ropes that crisscross the bags hold the fabric to the rover. The ropes give the bags shape, which makes inflation easier. While in flight, the bags are stowed along with three gas generators that are used for inflation.
Testing, Testing, Testing
Since the airbags are composed of many layers, some tearing in the outer layers is acceptable and even expected. Engineers test the bags to make sure there will be no catastrophic problems that would prevent a safe landing.
Mars airbag testing is done in world’s largest vacuum chamber at the Plum Brook Station of NASA’s Glenn Research Center in Ohio. “The Plum Brook facility is pretty impressive, along with all the people who operate it,” said Carson.
The test chamber used for the tests is a little over 30 meters (100 feet) across and about 37 meters (120 feet) high — big enough that three railroad tracks go through it. A test spacecraft and airbag system weighing about 535 kilograms (about 1,180 pounds) are accelerated with a bungee cord system onto a platform with rocks that approximate the Mars surface. The drop is at landing speed, about 20 to 24 meters (yards) per second.
Tests are documented thoroughly with high-speed and video cameras, in addition to visual inspections. Engineers even built a clear dome, studded with rocks, that has a camera that documents tests from a rock’s-eye view. During testing, a crew from ILC Dover, the airbag’s manufacturer, stands by to make quick repairs and to note any changes required.
“We do extensive testing,” said Tom Rivellini, deputy mechanical systems architect. “We want to break the bag on Earth, not on Mars. If we see a tear that is unexpected or goes too deep, we can make changes now [before the final design].”
Carson added, “We’ll go over all the data we’ve accumulated so far, do some more testing, and decide on a design configuration.”
And then on to Mars in 2003!