Divers

Air Force Study Points To Reusable Orbiter

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Newly declassified details of the analysis behind the U.S. Air Force’s decision to opt for a next-generation Reusable Booster System (RBS) reveal a long-term preference for a rocket-based, combined-cycle upper-stage orbiter over the nearer-term expendable solution.
The RBS plan is in development to replace the Air Force’s existing Evolved Expendable Launch Vehicles (EELV) beyond 2025, and aims to cut launch costs by 50% by combining a reusable first stage with expendable upper stages. The booster would take off vertically and return to a runway landing at the launch site.
Details revealed in the joint U.S. Air Force Space and Missiles Systems Center/Aerospace Corp. study at the American Institute of Aeronautics and Astronautics Space 2010 conference in Anaheim, Calif., show that while expendable upper stages will provide the initial capability, “a rocket-based combined cycle (RBCC) orbiter is the preferred far-term solution.” The RBCC configurations would adapt to the RBS first stage for vertical launch but return for a horizontal landing.
Although the study held out some optimism for RBCC proponents in the long run, its findings could be a telling blow for supporters of air-breathing turbine-based combined-cycle (TBCC) hypersonic space launch concepts. Study officials say even though the TBCC performance indicates greater specific impulse than rockets, the reusable booster turned out to be smaller, lighter and less costly.
Design details of a new reusable rocket and air-breathing combined-cycle hypersonic vehicle aimed at the long-term orbiter role have also been unveiled at Space 2010 by Astrox, a Maryland-based research and development company. The design was developed after the company was commissioned to perform a comparative survey of eight alternative two-stage-to-orbit (TSTO) configurations by the Air Force Chief Scientist Office, says Astrox President Ajay Kothari. These included Lockheed Martin’s Blackswift design for the Defense Advanced Research Project Agency, as well as Boeing’s FAST concept.
The RBCC design is the focus for an ongoing comparative study into reusable launch systems by the Air Force and NASA. The Air Force is evaluating a vertical launch system, and NASA a horizontal takeoff system. “We are about 85% complete with the study now, but the design is pretty much done,” says Kothari. Measuring around 158 ft. in overall length, the vehicle would carry a 20,000-lb. payload to low Earth orbit. After staging from the RBS at around Mach 3.5-4 and 75,000 ft., the vehicle would be powered by dual-mode ram/scramjets to a rocket transition point around Mach 10 and 95,000 ft.
Kothari believes the concept works where so many have failed because of the vehicle’s comparatively low dry weight. This is driven primarily by the move to a vertical takeoff, which reduces landing gear weight as well as wing size. The reduced loading demand on the gear for the vertical-launched concept restricts gear weight to around 5,000 lb. versus an estimated 35,000 lb. for the beefed-up gear of the horizontal takeoff version. The selection of an RBCC propulsion system over the turbine-based alternative also helps the equation with an installed engine weight of around one-fifth that of the turbine-powered vehicle.
The weight factors “work systematically to kill horizontal takeoff concepts, and the same thing happened with Blackswift. It also explains why horizontal takeoff has killed the possibilities that hypersonic technology could bring to this country, and that’s why we need to change the paradigm,” he adds.
The Air Force’s main focus remains for now on replacing the Atlas V and Delta IV with two versions of the RBS: a single reusable first stage and expendable cryogenic upper stage for medium-lift missions; and two reusable boosters and cryogenic core and upper stages for heavy-lift and growth missions. Initial operational capability is set for 2025, with EELVs being phased out in 2030.
Planning is underway to begin technology development for the reusable booster through two Air Force Research Laboratory demonstrators, more details of which were also revealed at Space 2010. The first is the RBS Pathfinder, already in initial planning and due to fly in 2013. A larger follow-on demonstrator, the RBX, is set to enter development in Fiscal 2012 and will be flight tested in 2016-17.
Although program officials say a solid concept demonstrator has yet to be completed, the outline Pathfinder is baselined with an NK-33 liquid oxygen (LOX)/kerosene rocket engine and will demonstrate the preferred “rocket-back” return-to-launch-site maneuver. The RBX, currently with a 60-ft. overall length, 34-ft. span and 9-ft.-dia. body, is designed as a demonstrator representative of the operational system. The vehicle is outlined with a gross liftoff weight around 230,000 lb. and will be powered by a LOX/kerosene RD-180 EELV engine. Another AFRL demonstration program—Hydrocarbon Boost—is developing a large LOX/kerosene rocket engine for the full-size booster.
As well as testing the rocket/fly-back maneuver, Pathfinder will help refine operational and rapid turnaround procedures and autonomous operations. RBX will test propulsion, avionics and airframe components to verify reusability.

Team reports most earthlike planet yet outside solar system

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A team from the University of California Santa Cruz and the Carnegie Institution of Washington Wednesday announced the discovery of what could be the first planet outside of the Solar System that makes a strong case for potentially being habitable.
"Our findings offer a very compelling case for a potentially habitable planet," Steven Vogt, a professor of astronomy and astrophysics at UC Santa Cruz and co-leader of the Lick-Carnegie Exoplanet Survey, said in a news release. "The fact that we were able to detect this planet so quickly and so nearby tells us that planets like this must be really common."
This discovery resulted from 11 years of observations of the nearby red dwarf star Gliese 581 using the HIRES spectrometer at the W. M. Keck Observatory in Hawaii. The instrument provided precise measurement of wobbles in the star's motion, allowing detection of orbiting planets.
A paper published in the Astrophysical Journal reported two planets around Gliese 581, bringing the the total known to orbit the start to six, the most discovered in a system outside of our own.
One of the planets, designated Gliese 581g, is in the middle of an area where liquid water could exist on the surface, has a mass three to four times that of Earth and orbits its star in just under 37 days, according to the researchers, who said its mass indicates that it is probably rocky, with a definite surface and enough gravity to hold an atmosphere. One side always faces the star.
Gliese 581 is 20 light years away from Earth in the constellation Libra and has about 30 percent of the mass of our sun. Two previously detected planets lie at the inner and outer edges of the habitable zone.

La création d'un moteur nucléaire spatial demanderait 6 à 9 ans (Roskosmos)

Il faudrait six à neuf ans pour concevoir un moteur nucléaire destiné aux expéditions interplanétaires, a annoncé mardi aux journalistes le directeur de l'Agence spatiale russe, Anatoli Perminov.
Grâce à un tel propulseur, "trois mois suffiraient pour effectuer un vol vers Mars et revenir sur la Terre après avoir passé 30 jours sur la planète rouge", a-t-il affirmé.
Selon le directeur de Roskosmos, un vaisseau doté d'un moteur de ce type pourrait atteindre Mars en un mois. Il faudra encore un mois à l'équipage pour y remplir sa mission et un mois pour regagner la Terre, a-t-il précisé.
Prié d'indiquer à quel stade se trouvait la conception du propulseur nucléaire spatial, M.Perminov a répondu: "Au stade de l'esquisse du projet".
D'après lui, cette idée a retenu l'attention de plusieurs pays, si bien que Roskosmos étudie actuellement la possibilité d'engager une coopération internationale dans ce domaine.

Lanceur russe Rockot

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Le lanceur léger Rockot sert à placer des satellites de moins de 2 t sur des orbites basses.

EADS : un projet de lanceur "low cost" pour la NASA !

EADS s'attaque au marché de l'espace américain ! Le groupe aéronautique européen, via sa filiale Astrium, a ainsi conclu un accord avec l'américain Alliant Techsystems, un des principaux fournisseurs de la NASA pour ses navettes spatiales, en vue de développer un lanceur commercial à bas coût, capable d'emporter des astronautes dans l'espace, écrit le 'Wall Street Journal' sur son site Internet.

L'accord devrait être officialisé dès ce mardi, précise encore le quotidien américain, qui souligne que l'initiative risque toutefois de se heurter à de vives oppositions politiques aux Etats-Unis, ainsi qu'à une forte concurrence de projets rivaux...

La course s'annonce en effet très disputée pour remplacer les navettes spatiales de la NASA, qui pa rtent en ce moment à la retraite. La NASA dispose d'un budget de 200 Milliards de Dollars pour les remplacer et souhaite se doter de lanceurs commerciaux capables à la fois de transporter du matériel et des astronautes dans l'espace, notamment vers la station spatiale internationale.

Selon le vice-président d'Alliant, Charlie Precourt, interviewé par le 'WSJ', le consortium américano-européen propose de réutiliser des parties de systèmes pré-existants pour élaborer sa fusée, et promet ainsi d'en accélérer le développement et d'en minimiser les coûts.

Le futur lanceur de 100 mètres de haut, pesant plus de 22 tonnes et doté de deux étages, aurait une puissance équivalente aux plus puissants lanceurs commerciaux actuels américains et européens. Le coût d'un lancement serait inférieur à 180 Millions de Dollars, un montant inférieur de 40% aux vols les plus chers proposés par une société commune Boeing-Lockheed Martin, a précisé M. Precourt.

International Asteroid Defense Plans Form

further step has been taken toward forming an international body that could plan for and respond to the threat of an asteroid impacting Earth.

The late August meeting in Pasadena, Calif., involved NASA, the European Space Agency and national space agencies from Germany and France. These are members of the United Nation’s Action Team-14, co-organizer of the workshop along with the Secure World Foundation (SWF) and the Association of Space Explorers.

Drawing on meetings last year in Germany and Mexico to discuss the threat of near-Earth objects (NEOs), the Pasadena workshop focused on plans to mitigate the effects of an asteroid strike, as well as developing an international model for the response to these threats.

“How should we respond to the threat of NEOs?” asks SWF Executive Director Ray Williamson. “How shall the space agencies organize themselves to deal with the response side of it? How do we generate the information and do the analysis that will lead to a warning at the appropriate time? What are the steps? There are very serious policy and legal issues about how to deal with these things internationally, and we’re not there yet. So these are first steps to thinking through a lot of those issues.”

Another key task will involve setting up a NEO Mission Planning and Operations Group (MPOG) that will plan, organize and conduct missions to threatening asteroids. The MPOG will be modeled along the lines of the inter-space agency group established to monitor space debris, Williamson says.

Action Team-14, part of the United Nations Committee on the Peaceful Uses of Outer Space Scientific and Technical Subcommittee, will present recommendations to the U.N. working group at a NEO-mitigation working group meeting in Vienna next February. The group’s report will then be passed on for review by a full committee meeting in June 2012, prior to completion of a set of recommendations on which the U.N. can act in February 2013.

In the meantime, Williamson says the group also will help get the MPOG started so that when the report to the U.N. is delivered there will be a structure in place to help execute the proposals.

The plan also includes widening the group to involve space agencies from China, Russia, India and others to contribute ideas and hardware. Chinese space officials were invited to the Pasadena meeting but were unable to attend because of visa issues.

The bottom line, Williamson says, is: “If a threat is detected, who actually says ‘Go forth and deal with it?’ It’s an international issue. Maybe we detect an asteroid that’s coming toward the U.S. but if we move it, we want to make sure we’re reducing the risk of dropping it on Europe, for example.” To help the group plan responses to various contingencies, it is running different NEO scenario simulations, as well as examining a range of potential missions to asteroids that would make safe candidates for experiments in techniques for altering orbital paths.

The group also was briefed on the latest results from NASA’s ongoing NEO survey, and in particular the alarming number of very small objects measuring less than 140 meters (460 ft.) that are being detected. “We’ve known they’re probably out there, but now suddenly — oh, gee. It’s like going down the highway blind, and suddenly the blinders come off and you see there’s another highway beside you with traffic coming in the other direction,” Williamson says.

Even this raises an issue. “How do you deal with the information should we discover one is heading to Earth? How do you handle that?”

Reusable Successor To EELV Moving Ahead

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A truly reusable, quick-response launch system has been an elusive dream of the U.S. Air Force since the dawn of the space age, but now the service is taking the first steps toward a real capability as plans for a reusable booster system (RBS) come together.

Dubbed Pathfinder, the demonstrator is a subscale vehicle aimed at proving the concept of a vertical-launch-and-horizontal-landing first stage. Researchers hope to show that by returning to an aircraft-like landing and being fully reusable, the system could cost up to 50% less to launch than the Air Force's current Evolved Expendable Launch Vehicle (EELV) family.

As all missions take place from coastal locations, the vehicle can only be recovered if it returns to land after launching the second-stage payload at a point somewhere above Mach 5.5 and 150,000 ft. altitude. For such a concept to be feasible, it must therefore be capable of executing a demanding about-turn or “rocket-back” maneuver, which has never been demonstrated before, and returning from downrange using its own rockets.

The Pathfinder vehicle—which is being developed under the Air Force Research Laboratory's (AFRL) RBS Flight and Ground Experiments (RBS-FGE) program—is designed to prove the concept. Pathfinder is expected to lead to a larger-scale demonstrator and, ultimately, a full-scale reusable successor to the current EELV family, which is being retired in 2030.

“The big driver is the rocket-back mission,” says Bruce Thieman, leader of AFRL's Affordable and Responsive Space Access Technology Transition effort. “Every launch you do has to go out over the water, so everybody has to be able to get back to land. So we have the problem of what to do at the staging point around Mach 5.5. How do we flip it back while still firing the engine and how to control the propellant inside the vehicle? So Pathfinder is going to help us understand the aero-thermal issues and guidance-and-control problems of doing that flip,” he says.

The project emerges from the Air Force's Strategic Master Plan for a range of satellite and counter-space launch capabilities. These include responsive spacelift; the ability to reposition, recover and service on-orbit assets; transport of objects from one terrestrial location to another using space; and the regeneration of satellite constellations. The RBS builds on the groundwork of the AFRL-led Future Responsive Access to Space Technologies (FAST) program, which focused on a series of ground experiments of airframe, structural health-monitoring and ground developments. FAST is now coming to an end, and the emphasis is shifting to the flight demonstrator.

AFRL expects to select a winning concept in the September-November period from the three designs submitted by Andrews Space, Boeing and Lockheed Martin. The first phase of the flight experiment in 2014 will be a vertical takeoff and a horizontal landing and probably going downrange at a little more than Mach 1 for an operational concept demonstration, says Thieman. “The next phase is to go downrange at higher speeds and go to higher altitudes. Flight-envelope expansion will take place in 2015.”



Testing will likely be conducted at either Edwards AFB, Calif., or White Sands Missile Range, N.M. “Each team will tell us what they plan to do, and it is part of their proposal,” he says. All are aimed at concepts similar to the 15-ft.-long reference Pathfinder revealed by AFRL in 2010, and are expected to test different profiles and gather data to map out a matrix for future flights.

More details of the three concepts are also emerging. The Andrews system resembles a simple, stub-winged version of a SpaceX-like Falcon booster, while the Boeing concept features a cranked delta wing with tip-mounted rudders. The Lockheed Martin concept is also delta-winged but is differentiated by the addition of canards. For propulsion, Lockheed Martin is developing a 20,000-lb.-thrust liquid oxygen/kerosene engine, while both Boeing and Andrews are believed to be studying the use of growth versions of XCOR engines.

Lockheed Martin is just beginning engine runs using a reactivated test site at its Space Systems Waterton facility near Denver. The rocket is already proving “very stable” during initial tests, says John Karas, vice president for human spaceflight and general manager. Although only running for 1-sec. bursts up until now, the plan is to extend run time until “we do full-duration firings by the end of the year.” The requirement for Pathfinder is an 80-sec. burn, he adds.

Lockheed's plan appears to be ahead of the schedule set by AFRL, which calls for engines to be up and running by February 2013. “We have to have an engine firing before we continue to go anywhere,” says Thieman. Individual proposals will also detail how they plan to boost and perform the rocket-back maneuver. “We've done it subsonically with the [McDonnell Douglas] DC-X at altitudes around 10,000 ft.—but that didn't involve the aerodynamic problems you are dealing with at these higher speeds and altitudes.”

Evaluation will also include “looking at how small the vehicle can be and still make it really traceable.” Teams must provide detailed analysis showing that their designs would represent a vehicle that could be sized up to the staging point of between Mach 5 and 6, and 150,000-200,000 ft. “So they're going to have to figure out a Pathfinder that's scalable,” says Thieman. The design must also be capable of cruising back at Mach 2-2.5 and be gliding back at sufficient speed and altitude when the fuel is exhausted.

The next stage beyond Pathfinder will be determined by the outcome of several studies now underway. The National Research Council is conducting an independent review that will be published in August. A commercial options study is also underway involving industry.

“The original plan was a large demonstrator in the $70-80 million range. The Rocketback Demonstrator [RBD] was going to do a Pathfinder function, and a decision was made to break it into two. So the decision is, should it be F-16-sized or bigger—around the size of the [F-15] Strike Eagle?” asks Thieman.

Payload or separation demonstrations will be performed by the larger variant and not by the Pathfinder. “The question is, can you save money by doing this? But there's no real hard data—this will be jointly done by AFRL and Space and Missile Systems Center [SMC] because the large demonstrator impacts what the prototype will look like. SMC has money in both, regardless of whether it's a Pathfinder followed by a small demonstrator or one that goes directly from a Pathfinder to a full-up vehicle,” says Thieman.

A large-liquid-engine group comprising the Air Force Space Command, propulsion researchers from AFRL and SMC's launch systems program office is also meeting to discuss engine options. The group will consider whether to focus on developing oxygen-rich, staged combustion engines like the Air Force's long-running Hydrocarbon Boost program, use an existing design or evolve a newer engine such as Pratt & Whitney Rocketdyne's J-2X. Whatever path is chosen would result in building a full-up “brassboard” engine capable of roughly 250,000 lb. thrust by 2020. The technology readiness level would be in the TRL 5 to 6 range at this stage, requiring several years of additional development to raise it to production-ready hardware readiness.