[ti:New Rocket Engine Could Cut Travel Time to Mars from Years to Months]
[by:www.21voa.com]
[00:00.00]更多听力请访问21VOA.COM
[00:00.04]A private company is working with
[00:02.84]the American space agency NASA
[00:06.04]to develop a new rocket
[00:08.56]that could greatly reduce space travel times.
[00:13.32]The engine for such a rocket will be designed
[00:17.48]to sharply increase the amount of thrust
[00:21.04]to speed up space travel
[00:23.40]and improve rocket efficiency.
[00:26.96]Thrust is the force
[00:29.16]that pushes a spacecraft through the air.
[00:32.48]It is produced by a propulsion system.
[00:36.24]Generally, a gas or liquid fuel
[00:39.84]is burned to produce thrust
[00:42.36]from the back of a spacecraft
[00:44.72]to propel it forward at high-speed.
[00:48.20]The new design,
[00:50.00]called Pulsed Plasma Rocket (PPR),
[00:54.28]is being developed by Arizona-based company
[00:57.96]Howe Industries.
[00:59.96]The company is currently in the early stages
[01:04.12]of studying the technology
[01:06.60]before building working engine models.
[01:10.08]In a recent statement, Howe Industries said
[01:14.52]such rocket technology will be needed
[01:18.12]to support NASA's plans to return humans
[01:21.92]to the moon and after that, possibly Mars.
[01:26.60]The space agency has also set a goal
[01:30.64]to build a long-term base in space.
[01:34.04]But one barrier to all these plans
[01:37.68]is the long travel times necessary
[01:41.08]with current spacecraft systems.
[01:44.40]NASA estimates the moon sits an average
[01:48.56]of about 382,500 kilometers from Earth.
[01:54.52]The exact distance changes
[01:57.92]because of the moon's orbit around Earth.
[02:00.68]The average distance from Earth to Mars
[02:04.72]is 225 million kilometers.
[02:08.56]NASA says a trip to Mars
[02:11.64]with existing spacecraft
[02:13.84]would take at least 200 days each way.
[02:17.88]Developers of the proposed Pulsed Plasma Rocket
[02:22.56]have said it could reduce travel time
[02:25.76]to the Red Planet to about two months each way.
[02:30.08]Howe Industries said its new design
[02:34.32]gives the rocket the ability
[02:36.52]to reach extremely high speeds
[02:39.64]to complete "reasonable" space travel times.
[02:43.60]The development team estimates its PPR system
[02:48.20]could produce up to 100,000 N of thrust.
[02:53.16]The ‘N' at the end of the number stands
[02:56.08]for Newtons, a unit of measurement for thrust.
[03:00.40]NASA has described its Space Launch System (SLS)
[03:06.64]as the most powerful ever built.
[03:09.76]The agency has said the SLS rocket system
[03:14.04]is expected to provide nearly
[03:16.60]53 N of thrust during space travel.
[03:20.96]Developers of PPR say that in addition
[03:25.08]to a huge increase in thrust,
[03:28.04]the new design also provides
[03:30.88]a "specific impulse" rate of 5,000.
[03:35.48]Specific impulse is a method for measuring
[03:39.52]– in seconds –thrust
[03:41.72]and efficiency levels of rocket engines.
[03:45.16]The higher this rate is,
[03:48.00]the more efficient the rocket system is.
[03:51.36]By comparison, the SLS rocket
[03:54.88]has specific impulse rates below 500.
[03:59.16]Officials at Howe have said the PPR
[04:03.68]is based on another plasma-based technology
[04:07.60]known as pulsed fission fusion.
[04:10.80]NASA says this process involves
[04:13.96]quickly pressing plasmas
[04:16.16]into high pressures to produce thrust.
[04:19.40]But the developers
[04:21.40]say the PPR system is smaller,
[04:24.68]simpler and costs less to operate.
[04:28.44]Howe's statement introducing the technology
[04:32.68]said the combination of extremely high thrust
[04:36.68]and higher specific impulse rate
[04:39.68]"holds the potential to revolutionize
[04:43.12]space exploration."
[04:45.60]The team said such a system
[04:48.64]should be able to propel much heavier spacecraft
[04:53.12]and support much longer trips
[04:55.88]to more distant areas of space.
[04:58.92]The planned system
[05:00.96]could also make it easier for spacecraft
[05:04.16]to be equipped with heavy shields
[05:06.80]to protect traveling astronauts
[05:09.44]from Galactic Cosmic Rays.
[05:13.00]These are highly energetic particles
[05:16.48]that move through space
[05:18.28]at nearly the speed of light.
[05:20.72]The rays can be harmful to humans in large amounts.
[05:25.48]The PPR project is one
[05:28.12]in a series of NASA development projects
[05:31.60]that recently received additional
[05:34.08]financial assistance to keep running.
[05:37.48]The projects are part of a NASA program
[05:41.08]called Innovative Advanced Concepts (NIAC).
[05:46.60]PPR is currently in Phase I of development.
[05:51.76]The team said if chosen by NASA
[05:54.60]to continue with Phase II,
[05:56.96]it will be centered on improving
[05:59.20]the performance of the proposed engine,
[06:02.32]as well as carrying out experiments
[06:05.24]on major engine systems.
[06:07.60]The last phase will involve
[06:10.20]completing a spaceship design
[06:13.00]for carrying humans to Mars.
[06:16.36]I'm Bryan Lynn. 更多听力请访问21VOA.COM
END OF TRACK. "END OF TRACK." The two men bowed. "Whoever was that person you were talking to?" she enquired, as soon as they stood together. The took of triumph faded from her eyes, she had grown worn and weary. The roses were wilting on the walls, the lights were mostly down now. Hetty, looking in to see if anything was wanted, found herself driven away almost fiercely. I only saw Master Jervie once when he called at tea time, The year 1747 was opened by measures of restriction. The House of Lords, offended at the publication of the proceedings of the trial of Lord Lovat, summoned the parties to their bar, committed them to prison, and refused to liberate them till they had pledged themselves not to repeat the offence, and had paid very heavy fees. The consequence of this was that the transactions of the Peers were almost entirely suppressed for nearly thirty years from this time, and we draw our knowledge of them chiefly from notes taken by Horace Walpole and Lord Chancellor Hardwicke. What is still more remarkable, the reports of the House of Commons, being taken by stealth, and on the merest sufferance, are of the most meagre kind, sometimes altogether wanting, and the speeches are given uniformly under fictitious names; for to have attributed to Pitt or Pelham their[112] speeches by name would have brought down on the printers the summary vengeance of the House. Many of the members complained bitterly of this breach of the privileges of Parliament, and of "being put into print by low fellows"; but Pelham had the sense to tolerate them, saying, "Let them alone; they make better speeches for us than we can make for ourselves." Altogether, the House of Commons exhibited the most deplorable aspect that can be conceived. The Ministry had pursued Walpole's system of buying up opponents by place, or pension, or secret service money, till there was no life left in the House. Ministers passed their measures without troubling themselves to say much in their behalf; and the opposition dwindled to Sir John Hinde Cotton, now dismissed from office, and a feeble remnant of Jacobites raised but miserable resistance. In vain the Prince of Wales and the secret instigations of Bolingbroke and Doddington stimulated the spirit of discontent; both Houses had degenerated into most silent and insignificant arenas of very commonplace business. "It certainly will be. Miss Widgeon," answered Maria, with strictly "company manners." "One who has never had a brother exposed to the constant dangers of army life can hardly understand how glad we all feel to have Si snatched from the very jaws of death and brung back to us." "Just plug at 'em as you would at a crow, and then go on your way whistlin'?" persisted Harry. "Hurroo!" echoed Hennessey; "that's the ticket." "Come forward, keeper," continued the baron, "and state how these arrows came into your hands!" "Yes." HoMEJULIA京香2018下载
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