Aero 版 (精华区)
发信人: bage (网事如疯·春心萌动), 信区: AerospaceScience
标 题: SpaceViews -- 2000 October 2(转载)
发信站: 哈工大紫丁香 (2000年12月23日17:14:48 星期六), 转信
【 以下文字转载自 bage 的信箱 】
【 原文由 hitsma@0451.com 所发表 】
[To stop receiving SpaceViews, please follow the UPDATED
instructions at the end of this message.]
S P A C E V I E W S
Issue 2000.40
2000 October 2
http://www.spaceviews.com/2000/1002/
*** News ***
NASA and Lockheed Martin Reach X-33 Agreement
A Busy Week at Baikonur
Discovery Cleared for October 5 Launch
Beal Aerospace Lays Off Workers, Restructures Rocket Program
Boeing/Hughes Deal Clears Final Hurdle
Report: Progress Shortage Threatens Mir
NASA's Next Mars Mission to Be an "Odyssey"
Scientists Find Source of Sun's Coronal Heating
TRW Unveils New Low-Cost Rocket Engine
Blast Wave from Gamma-Ray Burst Observed
SpaceViews Event Horizon
Other News
*** Letters to the Editor ***
Another Viewpoint on SETI
-----------------------ADVERTISEMENT------------------------
The Space Frontier Foundation's Space Frontier Conference 9
"Odyssey's Horizon"
Los Angeles, California, October 19-22, 2000
Come join the most important gathering of space pioneers on
Earth. From rocket jocks to leading astronomers to the top
new space entrepreneurs and government policy makers - if
you are a Real Player in space, you need to be at this
event! Sessions include NEO's, Space Transportation,
Commercial Space Stations, Lunar and Mars exploration and
development, and our new X-Treme Space session, including
grant prizes for the best leading edge human/space research
ideas.
Register at: http://www.space-frontier.org
or call 800-78-SPACE
-----------------------ADVERTISEMENT------------------------
*** News ***
NASA and Lockheed Martin Reach X-33 Agreement
NASA and Lockheed Martin announced Friday that they have
reached an agreement regarding the future of the troubled X-33 program
that will delay the first flight of the vehicle until 2003 -- if ever.
The agreement, reached after many months of negotiations,
approves plans to use liquid hydrogen tanks made of aluminum, rather
than lightweight composites, and revises the schedule of payments NASA
will provide Lockheed Martin as work on the vehicle, designed to test
technologies for future reusable launch vehicles, progresses.
The agreement also sets a target date for the first suborbital
flight of the X-33 in 2003, a year later than the worst-case estimates
of delays that were circulated earlier this year and four years later
than the original launch date of 1999 announced when the X-33 design
was selected in July 1996.
Replacement of the vehicle's composite tanks became necessary
after a tank was damaged during load tests at NASA's Marshall Space
Flight Center last November. The inner and outer layers, or
"facesheets", of one of four lobes of the tank cracked and separated
when pressure built up between the two layers after liquid hydrogen
was pumped out of the tanks at the completion of one such test.
A report completed earlier this year, but only released in
August, concluded that several technical issues caused the facesheets
to crack and separate. That report also blamed poor communications
among the engineers and technicians working on the tank, and concluded
that a more incremental "building-block" approach to tank testing was
needed, rather than the full-up tests on the entire tank then being
performed.
Because of the problems with the composite tank, NASA and
Lockheed Martin have agreed to replace them with tanks made of
aluminum. The aluminum tanks will be heavier than the composite ones,
but will have far fewer technical challengers that would further slow
down the program.
"The switch to aluminum tanks recognizes that the X-33 program
is a commercial challenge as well as a technical challenge," said Gene
Austin, NASA X-33 program manager at Marshall. "While composite
technologies are a promising part of future space transportation, they
require further research. The aluminum tank design still permits us
to realize our near-term vision of demonstrating the technologies for
a reusable, single-stage next-generation launch vehicle."
The new agreement puts more of an emphasis on ground tests of
critical technologies, as recommended by the panel that investigated
the tank failure. Additionally, the agreement restructures NASA's
payments to Lockheed Martin, tying them to completed testing and
delivery of other hardware and software systems this year.
The agreement does not provide any additional money to
Lockheed Martin, however. Current funding for the X-33 project will
end next March, even though NASA said Friday that the project will
need additional funding to complete the program.
NASA said that Lockheed Martin will have to apply for extra
funds through the agency's new Space Launch Initiative, a multi-
billion dollar program to develop the technologies for next-generation
launch vehicles. This leaves open the possibility that Lockheed
Martin might not any competition for those funds, effectively killing
the program unless the company decided to pay for the rest of the
program itself.
In the statement about the announcement, though, the agency
seemed to hint that such an outcome would not be likely. "NASA and
Lockheed believe it is critical to continue work to solve the last
remaining barrier to low-cost, reliable access to space," the
statement read.
NASA has put nearly $1 billion into the X-33 program since
1996, although the General Accounting Office reported last year that
the government may have spent up to an additional $300 million based
on other costs, such as overhead and research reimbursements, not
directly accounted for. Lockheed Martin and its industry partners
have put in several hundred million more under a cooperative agreement
with the agency.
The X-33 was originally presented as a scaled-down version of
the VentureStar, a single-stage to orbit (SSTO) vehicle planned by
Lockheed Martin. However, the design of the VentureStar has changed
considerably since the X-33's selection, including the addition of
longer wings, an external payload module and, ironically enough, the
replacement of a composite liquid hydrogen tank with an aluminum one.
Despite the problems with the hydrogen tank, other aspects of
the X-33 design have been progressing. Officials say that assembly of
the vehicle is 75 percent complete, with 95 percent of the vehicle's
components fabricated. All the vehicle's hardware, with the exception
of the new hydrogen tanks, will be completed by the end of the year.
In addition, the X-33's aerospike engine, a key piece of
technology the vehicle was designed to test, completed its first round
of testing earlier this year. Tests are scheduled to resume in
October with two of the engines running in tandem.
"X-vehicle programs are about taking risks and pushing the
envelope," said Austin. "That is how we break through barriers that
previously held us back."
A Busy Week at Baikonur
In one of its busiest weeks in recent memory, the Baikonur
Cosmodrome in Kazakhstan hosted the launch of four different rockets
placing a variety of military, commercial, and scientific satellites
into orbit.
The week got underway Monday when a Zenit 2 lifted off on
schedule from Baikonur at 6:10 am EDT (1010 UT). Its payload,
designated only as Kosmos 2372, was placed into orbit ten minutes
after launch, according to Russian reports.
Russian officials declined to identify the payload, but
western experts believe it to be a new class of reconnaissance
satellites known as Enisei. It's believed to be a more advanced
version of the Orlets reconnaissance satellite that, unlike its
predecessors, is capable of transmitting its photos electronically
rather than returning them via film capsules.
The launch is the second this year for the Zenit 2, after the
February launch of another Russian military satellite. It's also the
fourth launch this year for the Zenit family, counting two Zenit 3SL
launches for the multinational Sea Launch consortium. Another Zenit
3SL launch is tentatively planned for mid-October.
The following day a Dnepr-1 lifted off at 6:05 am EDT (1005
UT) September 26 from an underground silo at Baikonur. It placed its
payload of five microsatellites from Italy, Malaysia, and Saudi Arabia
into a 650-kilometer (400-mile) orbit inclined 65 degrees to the
Equator about 15 minutes after launch.
The launch was previously scheduled for last month, but an
initial launch attempt August 25 was scrubbed because of a programming
error that caused an automatic shutdown moments before launch. The
launch was rescheduled for the following day, but delayed again when a
first-stage propellant tank failed to pressurize as planned.
Kosmotras, the Russian company that markets the booster, then decided
to delay the launch about a month so that the entire rocket could be
replaced.
Two of the five satellites launched Tuesday, SaudiSat 1A and
1B, are twin 10-kg (22-lb.) spacecraft built for Saudi Institute for
Space Research. A third 10-kg spacecraft, named UniSat, will be used
by the University of Rome La Sapienza to take images and study cosmic
dust.
A second Italian satellite, the 54-kg (119-lb.) MegSat 1, will
be used for store-and-forward communications for an Italian
communications company of the same name. MegSat 1 is based on MegSat
0, a smaller satellite launched on a Kosmos-3M booster last year. A
fifth satellite, the 54-kg TiungSat-1, was built by Surrey Satellite
Technology for the Malaysian company Astonautic Technology for remote
sensing work and also carries a cosmic-ray experiment.
The launch was be the second for the converted SS-18 "Satan"
ICBM, a missile being phased out under arms control treaties. A Dnepr-
1 launched the UoSAT-12 microsatellite for Britain's Surrey Satellite
Technology Limited in April of 1999.
On Friday, a Soyuz rocket lifted off at 5:30 am EDT (0930 UT)
September 28 from Baikonur. Ten minutes later it placed its payload,
known only as Kosmos-2373, into a low-Earth orbit.
While Russians officials did not identify the Soyuz's payload,
it's believed to be a reconnaissance satellite, possibly of the Yantar
class. If so it would be the second reconnaissance satellite launched
in a week, after the Monday launch of a Zenit 2 carrying what's
believed to be a next-generation imaging satellite.
Baikonur's busy week ended Sunday night with the launch of a
Proton at 6:00 pm EDT (2200 UT, 4:00 am October 2 Baikonur time). It
placed into a transfer orbit the GE-1A communications satellite, an
A2100AX model communications satellite built by Lockheed Martin, and
the Blok DM upper stage that will boost the satellite into
geosynchronous orbit.
The satellite will be operated by Americom Asia-Pacific LLC, a
joint venture of GE Americom and Lockheed Martin Global
Telecommunications. The company plans to use GE-1A's 28 Ku-band
transponders to provide broadcast and telecommunications services to
India, China, and Southeast Asia from its position at 108 degrees east
longitude.
The launch was the fourth commercial flight of the Proton this
year, and the 17th since the formation of International Launch
Services, the joint venture of Lockheed Martin and Khrunichev that
markets the Proton to commercial customers. The launch was the 11th
overall this year for the Proton, counting military and civilian
government missions.
The next launch from Baikonur is not planned until later this
month, when a Soyuz rocket will launch a Progress cargo spacecraft to
the Mir space station. Another commercial Proton launch, of the GE-6
communications satellite, is also scheduled for the latter half of
October.
Discovery Cleared for October 5 Launch
NASA managers gave their approval Thursday for a planned
October 5 launch of the space shuttle Discovery on a mission to add a
major new component to the International Space Station.
After a flight readiness review Thursday, shuttle managers
concluded Discovery was ready for launch next week on mission STS-92.
Launch time is scheduled for Thursday, October 5 at approximately 9:38
pm EDT (0138 UT October 6) at Pad 39A of the Kennedy Space Center.
There have been few problems during the preparations for
launch since the shuttle was rolled out to the launch pad on September
11. A helium pressure test last week revealed a small leak in the
shuttle's main propulsion system, but the leak was repaired and the
shuttle passed a similar test on Tuesday.
Earlier in the week the online publication SpaceRef reported
that a defective O-ring in a solenoid in a power drive unit that
operates the rudder/speed brake in the shuttle's tail. A similar O-
ring is used as part of the actuator for Discovery's center main
engine, but an inspection of the actuator turned up no evidence of O-
ring damage, and the O-ring was considered acceptable for flight.
STS-92 will be one of the more ambitious shuttle missions
during the early assembly phase of ISS. The shuttle will deliver to
the station the Z1 truss, a component attached to the Unity module
that be the base for what will eventually be a lattice-work structure
that will serve as the station's backbone.
The Z1 truss will be attached to Unity using the shuttle's
robot arm. That will be followed by four consecutive days of EVAs, as
two pairs of astronauts -- Leroy Chiao and Bill McArthur as well as
Jeff Wisoff and Mike Lopez-Alegria -- attach power and data cables
between the truss and Unity. The spacewalkers will also attach a
third Pressurized Mating Adapter to Unity's exterior that will serve
as a docking port for future shuttle missions to the station after
modules occupy the port the shuttle currently uses.
The four spacewalks combined will last nearly 30 hours, longer
than any previous ISS mission and longer than any ISS assembly mission
in the near future. The crew will also briefly spend some time within
the station, offloading some final supplies for the first long-term
crew, scheduled to arrive in early November.
In addition to the four spacewalkers, the crew includes
commander Brian Duffy and pilot Pamela Melroy. Japanese astronaut
Koichi Wakata will serve as a mission specialist and operate the
shuttle's robot arm during the mission.
STS-92 will also mark a major milestone for NASA, as it will
be the 100th mission in the history of the shuttle program, dating
back to STS-1 in April 1981.
Assuming an on-time launch October 5 the 11-day STS-92 mission
would wrap up with a shuttle landing back at the Kennedy Space Center
at about 4:50 pm EDT (2050 UT) Monday, October 16.
Beal Aerospace Lays Off Workers, Restructures Rocket Program
Facing mounting cost and schedule problems, Texas rocket
company Beal Aerospace restructured its rocket development program
last week, resulting in the layoff of over half its workforce.
A Beal spokesman confirmed Thursday that the company laid off
about 80 employees September 22, leaving approximately 70 employees
with the Dallas-based company. The layoffs were part of an overhaul
of the company's plans to develop a large expendable rocket booster.
"Basically, the program is over budget and behind schedule,"
said spokesman David Spoede, "so we decided to refocus our efforts."
Instead of developing the various components of its BA-2
rocket in parallel, the company now plans to work on them in series,
starting with the rocket engines and tanks and moving on to other
components later.
The company has already made some progress on engines. In
March the company successfully tested the BA-810, the engine that will
power the booster's second stage. Capable of generating up to 3.6
million newtons (810,000 lbs.) of thrust, the BA-810 is the third most
powerful liquid-propellant engine ever developed, after the F-1 engine
used on the Saturn V's first stage and the RD-170 used on the Soviet
Union's Energia.
The company is currently working on an even more powerful
engine that will power the booster's first stage. Spoede said that
the company had planned to test that engine in April or May of next
year, but that it may now be delayed in the wake of the company's
restructuring.
The layoffs took many company employees by surprise. "It was
a shock to everyone," said one laid off Beal worker who asked not to
be identified. He noted that the company had been hiring new people
earlier that week, just days before the layoffs were announced.
"We were all pretty positive about the company" before the
layoffs, that worker added, but said that for those still working
there, "morale is pretty low right now."
Beal Aerospace was founded in 1997 by Andrew Beal, a Texas
banker who saw an opportunity to enter what promised to be a rapidly-
growing satellite launch market. Unlike a number of reusable launch
vehicle (RLV) companies that started up around the same time, Beal
focused on developing a powerful but simpler, and hence less
expensive, expendable rocket that would go after the lucrative
geosynchronous communications satellite market.
After considering and then rejecting a smaller booster, the
BA-1, the company focused on a large expendable booster, the BA-2.
Capable of placing 6,000 kg (13,200 lbs.) into geosynchronous orbit,
the booster would compete with the largest expendable boosters
currently available, such as the Ariane 5. The company planned to
launch the first BA-2 from Cape Canaveral in 2002, a date now subject
to delay.
Beal also set itself apart from other entrepreneurial launch
companies through its funding. Rather than seek venture capital, as
RLV companies did with limited success, Andrew Beal funded Beal
Aerospace using the profits from Beal Bank, of which he owns 99
percent.
Beal Aerospace has also encountered its share of controversy.
The company originally planned to develop a launch site on Sombrero
Island, a small, uninhabited island in the Caribbean near Anguilla.
Those plans have been put on indefinite hold by the company after
environmentalists helped delay a report assessing the impact the
launch facility would have on the desolate island. Plans to build a
rocket manufacturing facility in the Virgin Islands were similarly
blocked.
Earlier this year the company announced an agreement with the
government of Guyana, a small country on the northeast coast of South
America, to build a spaceport there. That agreement has not been
without controversy, either, since the launch site would be located in
a region of the country that neighboring Venezuela claims as its own.
The Venezuelan government has raised concerns about the spaceport,
claiming at times that the facility may be a cover for a U.S. military
base.
Boeing/Hughes Deal Clears Final Hurdle
Boeing's plan to buy the satellite division of Hughes
Electronics was approved by American and European regulators
Wednesday, cleared the way for the $3.75-billion deal to be completed.
The U.S. Federal Trade Commission (FTC) and the European
Commission (EC) both issued consent agreements Wednesday that will
allow Boeing to acquire Hughes Space and Communications (HSC), a
branch of Hughes Electronics -- itself a subsidiary of automaker
General Motors -- that is one of the leading manufacturers of
communications satellites in the world.
The agreement required regulatory consent by the two bodies
because of concerns that the acquisition of the satellite maker by
Boeing, one of the world's leading launch vehicle providers, could
create an anti-competitive environment by allowing the exchange of
information about competing satellite and launch vehicle companies.
Under the agreements, a "firewall" will be established between
Boeing's launch vehicle division and Boeing Satellite Systems (BSS),
as HSC will be known after the acquisition, that will prevent the
satellite division from sending private information about other
companies' boosters to the launch vehicle division. Likewise, the
launch vehicle division will be prohibited from exchanging private
information about other companies' satellites with BSS.
In addition, the FTC agreement prohibits Boeing from providing
"systems engineering and technical assistance" for a classified
military program after Pentagon officials raised concerns that the
deal could lead to increased costs of the unspecified program. The
FTC also appointed Sheila Widnall, former Secretary of the Air Force,
as a monitor to make sure the terms of the agreement are followed.
"This consent agreement will ensure that competition in the
highly specialized markets for satellites and launch vehicles will be
maintained," Richard Parker, director of the FTC's Bureau of
Competition, said in a statement.
Because Boeing does not currently have a major commercial
satellite business, European regulators were convinced that the
acquisition would not adversely impact other commercial satellite
firms, such as Lockheed Martin, SS/Loral, Astrium, and Alcatel.
"Following the results of the Commission's detailed
investigation, it appears that HSC is and will remain subject to the
competition from other large satellite prime contractors," the EC said
in a statement.
With the regulators' approvals, Boeing plans to quickly
complete the acquisition of HSC and two other smaller companies owned
by Hughes. "We plan to close the purchase of Hughes Space and
Communications company, Electron Dynamics and Spectrolab from Hughes
Electronics Corporation on October 6, 2000," said Boeing president
Harry Stonecipher.
Hughes will retain its satellite services business, which
includes DirectTV as well as a majority stake in PanAmSat. Hughes
will continue to use satellites built by the former HSC, but will also
be able to purchase satellites from other manufacturers, something the
EC noted in its decision to approve to the deal.
"It appears that HSC's [position] will probably not be
significantly strengthened as a result of the transaction since HSC's
severance from the Hughes group will not create new major
opportunities for HSC, and might instead cause HSC to lose the custom
of Hughes' satellite operating companies, which represented
approximately 45% of HSC's satellite orders between 1997 and 1999,"
the EC noted.
Boeing and Hughes first announced the acquisition in January,
noting at the time that it was subject to regulatory approval.
Report: Progress Shortage Threatens Mir
A potential lack of Progress resupply spacecraft, coupled with
a higher-than-expected decay rate, poses a new danger for the Russian
space station Mir according to a report published Friday.
AviationNow.com reported that officials with MirCorp, the
company leasing the station, now expect to use more Progress
spacecraft than originally planned to reboost the station's orbit.
The station's orbit is decaying faster than predicted because of
increased atmospheric drag as increased solar activity expands the
tenuous upper atmosphere.
MirCorp president Jeffrey Manber told the publication that if
no Progress spacecraft were launched before December, the spacecraft's
orbit would dip low enough that it could no longer be controlled.
That is not expected to happen, however, since MirCorp has funded the
launch of a Progress currently scheduled for the middle of this month.
The company said it will need to fund more Progress flights
than originally planned to maintain the station's orbit. This may put
a strain on the company's finances, particularly since it has had
difficulty attracting new investors, but Manber told AviationNow that
current investors plan to pump tens of millions of dollars into then
company to make up for the current shortfall.
The funding shortfall has also forced MirCorp to scale back
its plans for upcoming missions to the station. The next crew
scheduled to launch to Mir was to spend several months on the station,
but that mission has been scaled back to two weeks. That flight will
largely be supported by Dennis Tito, a California businessman who is
paying approximately $20 million to be the first "citizen explorer",
or commercial space tourist, to visit the station.
This requirement for additional Progress flights also opens
the question of whether RSC Energia, the Russian company than
manufactures the spacecraft, will be able to meet the requirements of
Mir and the International Space Station, which will also use Progress
spacecraft to transfer supplies and help reboost its orbit.
Energia officials have said in the past that they have the
capacity to meet the needs of both stations, but funding is a larger
issue. AviationNow reported that MirCorp is about two weeks behind on
its payments to Energia, which is also MirCorp's majority shareholder.
MirCorp said it should have the funds soon to pay for the October
Progress flight.
Energia officials have also said that the Russian government
has been slow to pay for the Progress and Soyuz flights to ISS, to the
point where the company has been forced to pay for those flights
themselves. A meeting between officials of Energia, MirCorp, the
Russian government, and other organizations is reportedly planned for
later this week to discuss the current situation.
"The agenda of this meeting is: given the solar flare
activity, given the requirements of ISS, given the requirements of
MirCorp, given the presumed level of funding possible for MirCorp,
given the apparent inability of the Russian government to support us -
what can we do next year," Manber told AviationNow.
NASA's Next Mars Mission to Be an "Odyssey"
In recognition of one of the classics of the science-fiction
genre, NASA officials announced Thursday that the agency's next
mission to Mars will be named "2001 Mars Odyssey".
NASA confirmed a number of rumors circulating on the Internet
on Thursday when it said the spacecraft, formerly known as the "Mars
Surveyor 2001 Orbiter" would be renamed in part to recognize the
famous movie and the novel upon which it was based.
"The year 2001 has a special significance to many of us who
recall the thrill of reading the book and watching the movie '2001: A
Space Odyssey,'" said Scott Hubbard, NASA's Mars program director.
"We looked forward to the exciting future of space exploration that
the year 2001 promised."
The spacecraft, the only one NASA is sending to Mars during
the next launch opportunity, is scheduled for launch on April 7, 2001,
on a Delta 2 from Cape Canaveral, Florida. It will enter a temporary
orbit around the Red Planet six months later and spend two months
aerobraking to achieve its final orbit.
2001 Mars Odyssey will carry three primary instruments. The
Thermal Emission Imaging System (THEMIS) will use a camera and
infrared spectrometer to determine the mineral composition of the
Martian surface and its morphology. A Gamma Ray Spectrometer (GRS)
will study the elemental composition of the surface and subsurface,
looking in particular for traces of hydrogen that could be evidence of
past or present water. The Mars Radiation Environment Experiment
(MARIE) will study the radiation environment in orbit and how it might
affect future human missions to the planet.
The mission will be the first to Mars for NASA since the twin
failures of the Mars Polar Lander and Mars Climate Orbiter missions
last year. Those failures led to a near-complete revision of NASA's
Mars exploration plans: 2001 Mars Odyssey is the only mission planned
before those failures that is still being carried out on its original
schedule.
The orbiter was to be one of two missions to Mars launched
next year, as NASA planned to launch a lander mission as well.
However, the lander was canceled earlier this year in wake of last
year's failures, in part because the design of the lander was closely
based on Mars Polar Lander. Review panels also recommended some
changes in the orbiter mission, which project officials said have been
implemented.
"We have done several things in response to the NASA review
board recommendations to ensure mission success, like adding
additional staff and transitioning development personnel to
operations," said 2001 Mars Odyssey project manager George Pace. "I'm
confident we have a solid mission."
The 2001 orbiter will be followed at the next launch
opportunity in 2003 with twin rovers that will land in separate
regions of the planet. At the same time ESA will be launching its
first Mars mission, Mars Express, an orbiter that will also carry the
British-built Beagle 2 lander.
"NASA's next mission to Mars, launching in the year 2001,
represents the start of a new wave of exploration at the Red Planet,"
said Hubbard. "It seemed fitting to name the mission 2001 Mars
Odyssey not only in honor of the story and the movie, but also to
herald the start of our new long-term journey to explore Mars."
Hubbard noted that Arthur C. Clarke, who wrote the novel
"2001: A Space Odyssey" in 1968 and worked with the late filmmaker
Stanley Kubrick on the movie based on it, has "enthusiastically
endorsed" the new name for the Mars mission.
Scientists Find Source of Sun's Coronal Heating
Scientists said Tuesday that studies of giant loops of
superheated gas have revealed the likely source of the energy that
heats the Sun's corona to temperatures of millions of degrees.
The researchers used data from NASA's Transition Region and
Coronal Explorer (TRACE) spacecraft to conclude that the heating in
the lower regions of the corona provided the energy to heat the gas in
the corona, although they have yet to identify the mechanism that
heats it.
"The mysterious energy source that makes the Sun's atmosphere
so incredibly hot has been an enigma for more than 70 years, and
before we discover what it is, we needed to learn where it is," said
Markus Aschwanden of the Lockheed Martin Solar Astrophysics Laboratory
(LMSAL) in Palo Alto, California.
The discovery came from studies of coronal loops, streams of
gas that rise hundreds of thousands of kilometers high -- large enough
to encompass 30 Earths -- before falling back to the solar photosphere
at speeds of 100 kilometers per second (60 miles per second).
Astronomers had thought that the loops were heated evenly
throughout, and would thus be hotter at their tops, where the gas is
thinner and thus does not radiate away its heat as effectively.
Instead, the TRACE data revealed that the loops are actually composed
of a number of individual loops bundled together, and that, on
average, the temperature of the individual loops varies much less than
predicted by uniform heating hypotheses.
"Since a loop loses heat most rapidly from its bases, most of
the heat must also be going in at the bases for the loop to be at a
uniform temperature," said Karel Schrijver of LMSAL. "If this were
not so, the lower parts would have been much cooler than the tops,
which do not lose heat as quickly."
The extremely high temperature of the corona, the tenuous
atmosphere that extends for millions of kilometers from the Sun, has
been one of the biggest mysteries of solar science. Astronomers have
spent decades trying to understand why the corona can reach
temperatures of millions of degrees, while the photosphere, or solar
"surface", is far cooler, at less than 6,000 degrees Celsius (11,000
degrees Fahrenheit).
Discovering that the heating of the corona is taking place at
relatively low altitudes is the first step towards understanding the
mechanism that heats the corona. "Locating the source of coronal
heating is a key piece of this puzzle, and we are excited that solar
observatories like TRACE are allowing us to resolve the hidden events
occurring in the atmospheres of stars," said Aschwanden.
Some scientists believe that the Sun's magnetic field is
involved with the heating of the corona. In 1997 scientists found
that electrical currents travelling along magnetic loops extending
high into the corona provided more than enough energy to heat the
corona, but were unable to describe both how the magnetic loops formed
and how the energy would be transferred from the current loops to the
gas.
TRACE, an Small Explorer-class spacecraft launched in April
1998 on a Pegasus XL, is designed to study the "transition region"
between the photosphere and corona in an effort. The small spacecraft
studies the Sun at ultraviolet wavelengths from a polar low-Earth
orbit using a 30-cm (12-in.) telescope.
TRW Unveils New Low-Cost Rocket Engine
Aerospace company TRW announced Monday it had successfully
test-fired a large rocket engine that could significantly reduce the
cost of future launch vehicles.
The liquid hydrogen-liquid oxygen Low Cost Pintle Engine
(LCPE) completed test firings recently at NASA's Stennis Space Center
in Mississippi that reached 65 to 100 percent of its rated thrust, 2.9
million newtons (650,000 lbs.)
LCPE differentiates itself from the handful of other new
rocket engines developed in the U.S. in the post-Apollo era through
its low-cost design. "Most engines are designed for maximum
performance and minimum weight, but we deliberately set out to develop
an engine that minimizes cost while retaining excellent performance,"
said Al Frew, vice president and general manager of TRW's Space and
Technology Division.
Several factors contribute to the engine's low cost. The
engine uses common steel alloys that are cheaper than the lightweight
high-performance alloys used in other engines. The engine also uses a
simple ablative cooling design, rather than a more complex
regenerative cooling technique used in other engines.
Another key to the engine's design is the engine's simple
injector system. The engine features a single injector that allows
fuel and oxidizer to enter the engine and mix. The injector uses a
central pin -- a pintle -- that even spreads out the oxidizer and can
also be used to throttle the engine.
This simple system, which requires only five major parts,
stands in contrast to propellent injectors in other engines, which
usually require a number of injection points distributed evenly around
the diameter of the top of the engine's combustion chamber.
Pintle injectors are not new, having been developed in the
mid-1950s, but have not been widely used. A pintle injector was used
in the descent engine of the Apollo Lunar Module, and more recently
small versions of it were tested for Brilliant Pebbles, a proposed
missile defense system.
"We believe this engine will cost 50 to 75 percent less than
comparable liquid hydrogen boosters," said Frew. "By reducing engine
costs, which make up almost half of the cost of a launch vehicle, we
will reduce the cost of launch vehicles and access to space for
government and commercial customers."
To date there are no launch vehicles currently planning to use
the LCPE. TRW hopes to entice launch vehicle designers, though, with
the engine's low cost and scalability: versions of the LCPE could be
easily designed to power anything from small to very large launch
vehicles, according to the company.
Tests of the LCPE are scheduled to continue through the end of
the year at Stennis under a cooperative agreement with NASA. "This
testing is an important first step in validating that a low-cost
pintle engine can substantially lower the cost of future launch
vehicles," said LCPE program manager Kathy Gavitt.
LCPE is not the only new engine that has been tested recently.
In March Texas-based Beal Aerospace test-fired its BA-810 engine, an
engine capable of 3.6 million newtons (810,000 lbs.) of thrust. That
engine will be used on the second stage of the company's BA-2
expendable booster the company is currently developing.
Testing is also slated to resume in October on Rocketdyne's
XRS-2200 aerospike engine, which will be eventually used on NASA's X-
33 reusable launch vehicle technology demonstrator. The engine
completed a first set of tests in May in a single-engine
configuration; the October tests will investigate firing two engines
in tandem.
Blast Wave from Gamma-Ray Burst Observed
Astronomers announced this week that they have, for the first
time, observed the blast wave emanating from a powerful gamma-ray
burst (GRB).
In a paper to be published in the journal Astrophysical
Journal Letters, researchers from Notre Dame University and the
Harvard-Smithsonian Center for Astrophysics described how they were
able to serendipitously resolve the blast wave of the distant GRB.
Astronomers used a technique called "gravitational
microlensing", where the gravity of an intermediate object -- in this
case a small star half the mass of our Sun -- bends light from the
more distant object like a lens, magnifying the appearance of the
distant body.
The observations of GRB 000301C, conducted in March at the
Smithsonian's Whipple Observatory in Arizona, showed that the blast
wave appeared as a rapidly-expanding ring, in accordance with
theoretical predictions. Because of a quirk in special relativity,
the ring appears to expand faster than the speed of light, although no
element of the ring is exceeding light speed.
Resolving the blast wave of a GRB has never been done before
because such objects are thought to be very distant, and the rings too
small to be resolved with even the best telescopes. Astronomers
compared observing the ring to trying to resolve the letter "o",
printed in an ordinary type size, on the surface of the Moon.
"This discovery really confirms what we thought a gamma-ray
burst shock should look like," said Peter Garnavich of Notre Dame.
"To be able to resolve an explosion so far away is really quite
astounding."
What generates GRBs remains a mystery to astronomers, however.
A wide variety of hypotheses have been put forward to explain their
existence, from colliding black holes to "hypernova" explosions of
massive stars.
SpaceViews Event Horizon
Note: You can now add these events to your Palm handheld by clicking
on, or copying and pasting into a Web browswer, the URL below each
event. Visit Coola's Web site at http://www.coola.com/ for more
information about this free service.
October 3 Rally for Mars Exploration, Univ. of Massachusetts
Boston
http://www.coola.com/cgi-bin/addinfo.cgi?pid=10003&rid=969882294&type=D
October 4-10 World Space Week 2000
http://www.coola.com/cgi-bin/addinfo.cgi?pid=10003&rid=969880188&type=D
October 5 Launch of the shuttle Discovery on mission STS-92 from
the Kennedy Space Center, Florida, at 9:39 pm EDT
(0139 UT Oct. 6)
http://www.coola.com/cgi-bin/addinfo.cgi?pid=10003&rid=969879626&type=D
October 6 Ariane 4 launch of the Japanese N-SAT-110
communications satellite, from Kourou, French Guiana
http://www.coola.com/cgi-bin/addinfo.cgi?pid=10003&rid=969880023&type=D
October 7 Pegasus XL launch of NASA's High Energy Transient
Explorer 2 (HETE-2) spacecraft from an L-1011
aircraft based out of Kwajalein Missile Range in the
Pacific Ocean at 1:35 am EDT (0535 UT).
http://www.coola.com/cgi-bin/addinfo.cgi?pid=10003&rid=969879878&type=D
October 12 Atlas 2A launch of a DSCS military communications
satellite from Cape Canaveral, Florida at 7:33 pm EDT
(2333 UT).
http://www.coola.com/cgi-bin/addinfo.cgi?pid=10003&rid=970442592&type=D
October 19-22 Space Frontier Conference 9, Manhattan Beach,
http://www.coola.com/cgi-bin/addinfo.cgi?pid=10003&rid=968079287&type=D
October 20-22 Mars Week 2000, MIT, Cambridge, Massachusetts
http://www.coola.com/cgi-bin/addinfo.cgi?pid=10003&rid=969270315&type=D
October 23-27 32nd Annual American Astronomical Society Division for
Planetary Sciences Meeting, Pasadena, California
http://www.coola.com/cgi-bin/addinfo.cgi?pid=10003&rid=968079363&type=D
Other News
Calibrating a Cosmic Yardstick: A new measurement of the distance to
a relatively nearby star may be the first step towards a better
understanding of the size and nature of the universe, astronomers at
JPL and Caltech said last week. Reporting in the September 28 issue
of the journal Nature, scientists said they used the Palomar Testbed
Interferometer, a pair of 40-centimeter (16-inch) telescopes located
110 meters (360 feet) apart atop Palomar Mountain in southern
California, to accurately measure the angular size of the star Zeta
Geminorum, a Cepheid variable. This, coupled with other data, allowed
them to determine the star was 1,100 light-years from the Earth with a
precision much higher than past measurements. Cepheids have a known
relationship between their period and luminosity that makes them "cosmic
yardsticks" for measuring the distance to more distant galaxies;
astronomers believe work like this will help them better calibrate
those distances, and in turn refine measurements of the Hubble
Constant, a measure of the expansion rate of the universe.
Galaxy 8-i Satellite Problems: PanAmSat announced last week it is
working on a backup plan in the wake of an apparent failure of
stationkeeping thrusters on its Galaxy 8-i spacecraft. While a backup
system on the Hughes HS 601HP spacecraft should continue to work
through the end of 2002, the company said Galaxy 3C, another satellite
scheduled for launch next year, will take over for Galaxy 8-i, while
the company also works out a deal to build another satellite, Galaxy
8-iR. The problem with the spacecraft's xenon ion propulsion system
(XIPS), a small ion thruster system, is believed to be isolated to
that spacecraft and should not pose a problem for similar systems on
other HS 601HP and HS 702 spacecraft. Galaxy 8-i was launched in
December 1997 and was designed to last 15 years in orbit. The
spacecraft is used by Galaxy Latin America to provide DIRECTV
broadcasts throughout Latin America.
Milestones for New Large Telescopes: The first of twin 6.5-meter
(256-inch) Magellan telescopes in Chile marked "first light" on
September 15 when it took an image of NGC 6809, a star cluster 20,000
light-years away. Astronomers at Carnegie and the project's other
universities -- the University of Arizona, Harvard University, MIT,
and the University of Michigan -- plan to use the telescopes atop
Cerro Las Campanas to provide them with access to southern hemisphere
skies for studies ranging from observations of distant, high-redshift
objects to research into the large-scale structure of the universe.
Meanwhile, the MMT Observatory, a near twin of the Magellan telescope
thousands of kilometers to the north in Arizona, made another step
towards completion with a successful test earlier in the month of a
wide-field camera. Originally the Multiple Mirror Telescope, the
observatory's six 1.8-meter (72-inch) mirrors have been replaced with
a single 6.5-meter mirror from the same University of Arizona lab that
made the Magellan mirror.
Cameron to Mir? Famed director James Cameron is reportedly
negotiating with Russian officials for a flight to Mir or the
International Space Station, SPACE.com reported Friday. Cameron
reportedly spent several weeks in Russia talking with officials and
undergoing some physical examinations in preparation for a possible
future spaceflight. A spokesperson for Lightstorm Entertainment,
Cameron's production company, said his trip to Russia was for
"research" only, but Cameron in the past has expressed an interest in
traveling into space. Cameron, who won an Oscar for the movie
Titanic, is currently working on a number of Mars-related projects,
including a miniseries based on Kim Stanley Robinson's "Red Mars"
trilogy.
Apollo Award Bill Passes House: The house of Representatives approved
legislation last week that would give each Apollo astronaut an award
that features a small lunar sample. H.R. 2572, the Apollo Exploration
Award Act of 2000, would direct NASA to design a provide an award for
each astronaut (or surviving family) that flew Apollo missions between
1968 and 1972. A central feature of the award, as specified in the
legislation, would be a small lunar rock sample that could be removed
and examined. The legislation would prohibit the award from being
sold or otherwise transferred, expect to a family member. While NASA
has expressed some resistance to the legislation, the bill passed the
House by a margin of 419-0. The bill has yet to be considered by the
Senate, however, and Congress plans to adjourn in a week.
Briefly: For those interested in NBC's "Destination Mir" program, the
network has set up a web site at http://www.nbci.com/mir where you can
sign up for a mailing list to be informed of the latest updates about
the program. Note that to sign up, you must be an "NBCi member",
which is free save for the demographic information you have to
provide... Project Voyager, the new media startup cofounded by Carl
Sagan's widow Ann Druyan and Internet entrepreneur Joe Firmage, has
officially changed its name to OneCosmos. The site plans to launch on
January 1; a beta version of the site is currently online at
http://www.onecosmos.net as basically a set of links to science news
articles on other sites... SPACE.com announced a restructuring last
week that resulted in the layoffs of 22 of its 108 employees. Company
president Sally Ride also stepped down earlier in the week to pursue
science education opportunities elsewhere. [Editor's Note: SpaceViews
was acquired last year by Starport.com, which in turn was acquired by
SPACE.com earlier this year. This current restructuring should have
no immediate impact on SpaceViews, however.]
*** Letters to the Editor ***
Editor's Note: Letters to the editor on any article published in
SpaceViews can be sent to letters@spaceviews.com.
Another Viewpoint on SETI
In your article on SETI ("SETI Comes of (Middle) Age",
http://www.spaceviews.com/2000/09/article2a.html), you stated, "...and
dozens of extrasolar planets have all raised awareness within the
scientific community as well as the general public that life --
including potentially intelligent life -- may be widespread within the
universe."
I don't think that this is scientifically accurate. Extrasolar
planets, all of which are in zones or have properties inhospitable to
life, do not add to a belief that life may be widespread. Quite the
opposite, lifeless planets are just that, lifeless.
Astronomers are well aware that we can eliminate millions of
star systems for life just based on properties such as star size, age,
luminosity, or from multiple stars in the system. Millions more can
be eliminated because of proximity to other systems, galactic centers,
or ones that are too far from the galactic center. More and more
limitations on life are being found causing the probability of
widespread life to plummet.
I'm not saying there isn't any life out there. But the facts
of science are telling us it is quite rare. The old statistical
argument of "there are billions of stars so there must be billions of
beings" has given way to reality. I think the mindset in the SETI
community isn't as "positive" as some think because of these facts.
For example, the mood at the International Society for the
Study of the Origin of Life (ISSOL) 1999 conference has been described
as "grim." Report after report at the conference questioned our
understanding of origins and revealed that "widespread life" is quite
unlikely.
Understand that I write this as someone whom wanted to see the
universe filled with life. But logic and the related scientific
method dictate we follow the facts where they lead. They lead to a
rather lifeless universe.
Darrick A. Dean
New Castle, PA
========
This has been the October 2, 2000, issue of SpaceViews.
SpaceViews is also available on the Web at:
http://www.spaceviews.com/
or via anonymous FTP from ftp.seds.org:
ftp://ftp.seds.org/pub/info/newsletters/spaceviews/text/20001002.txt
*** UPDATED ***
To unsubscribe from SpaceViews, send mail to:
listserv@listserv.space.com
In the body (not subject) of the message, type:
unsubscribe spaceviews
*** UPDATED ***
For editorial questions and article submissions for SpaceViews,
including letters to the editor, contact the editor, Jeff Foust, at
jeff@spaceviews.com
For questions about the SpaceViews mailing list, please contact
jeff@spaceviews.com.
--
※ 转载:．哈工大紫丁香 bbs.hit.edu.cn．[FROM: es.hit.edu.cn]
Powered by KBS BBS 2.0 (http://dev.kcn.cn)
页面执行时间：610.007毫秒