#科技头条#【美“猎户座”载人飞船今日试飞!】

#科技头条#【美“猎户座”载人飞船今日试飞!】美宇航局消息,猎户座载人飞船定于美国东部时间5日07:05发射。昨日的尝试因为船只驶入、风力过大、助推器阀门故障等原因推迟。猎户座是美新一代载人航天工具,未来将搭载人类去火星。此次飞行高度将达5800千米,是国际空间站飞行高度的15倍。

http://www.dailymail.co.uk/sciencetech/article-2860511/Countdown-Orion-s-lift-Spacecraft-embark-historic-test-flight-usher-new-age-space-exploration.html

Nasa's historic Orion craft gets green light for Friday morning blast off: Space agency 'very confident' it has fixed valve flaw that scuppered first attempt at launch

The maiden launch of the Orion spacecraft has been postponed until 12.05 GMT (07:05 ET) on Friday, after a series of delays hampered efforts to blast in into space early on Wednesday morning..

Wind gusts and a sticky valve forced the Cape Canaveral team to call off today's test flight, which would have marked a new era in space exploration.

Instead, Nasa said crew had spent the day re-testing the systems - and said they were 'very confident' they would work perfectly at the second attempt 

Adding to the delays, a rogue boat strayed into the danger zone around the launchpad preventing the unmanned rocket from making its scheduled early morning lift-off.

If all goes to plan, Orion will tomorrow be catapulted around the Earth twice in a 4.5 hour journey, before re-entering the atmosphere at 20,000 mph (32,000 km/h).

The mission is unmanned, but in the future Nasa hopes to use the spacecraft to send astronauts to an asteroid in the 2020s and ultimately take them to Mars in the 2030s. 

Nasa crew worked late into the night to ensure fill-and-drain valves on the Delta IV Heavy were tested thoroughly before a second launch window opens on Friday morning. 'Our plan is to fly tomorrow,' said Mark Geyer, Orion program manager.

Friday's launch window will be 2 hours, 39 minutes, officials said in a briefing today.

'Our plan is to fly tomorrow,' said Mark Geyer, Orion program manager.

Fill-and-drain valves on the Delta IV Heavy have been tested throughout the day so the launch team can prevent a mechanical problem like one that came up Thursday.

 'We're very confident we're going to be able to exonerate the equipment,' said Dan Collins, chief operating officer of United Launch Alliance.  

Experts said the delay had taught them more about the craft, as it switched to internal battery power and saw other changes through the lead-up to launch and then through the three attempts at different points in the launch window.

'The spacecraft worked extremely well,' said Mike Hawes, Lockheed Martin's program manager for Orion, part of the team that built Orion for NASA and is operating this mission. 

'The systems did just like the simulators told us they'd do.'  

Experts told MailOnlne the delay was a major blow for the hundreds who has travelled to see the spectacle. 

'It's a little bit sad, it came quite unexpected,' space expert Remco Timmermans of World Space Week, who was out at the launch site, told MailOnline.

'It was a very long launch window, we've been here for a few hours, so it's a big disappointment.

'People are deciding whether to come back tomorrow. Some will, and some can't. We're a little bit depressed.

'The Delta IV has always been a very reliable launcher, so this is rather unusual for a launcher that is so well proven. I'd say we have a 50:50 chance of launching tomorrow, at a wild guess.'

One of the issues with launching tomorrow is that the weather is expected to be worse than today - which means ground winds could again be a problem. 

The weather for Friday is forecast to be a bit worse than Thursday, though still favorable, Nasa said.

Meteorologists are calling for a 60 percent chance of acceptable conditions. 

Dr Nigel Bannister, an expert in rocket propulsion at Leicester University, said: 'The weather is not looking that great for tomorrow and Nasa will want to wait until the weather conditions are right.

'Although there are specific windows in which they can launch, they will not want to risk it in the wrong environmental conditions.

'Rockets are not like aircraft - once they are moving and the bolts holding it to the launch pad have been released, there is no going back.

Delayed: Orion was set to launch at 12.05 GMT (07:05 local time) today, but wind gusts temporarily delayed lift-off with less than four minutes left in the countdown. Nasa now plans to attempt launch at the same time tomorrow

'Weather is a big issue for them. A rocket leaves behind a plume of gas that is extremely electrically conductive, and that turns a rocket into a giant lightning rod, so they will never risk launching if there are thunder clouds in the area.

'Wind shear can create extremely high stresses that need to be corrected very quickly so it is safer not to launch than risk losing a spacecraft that cost millions of pounds to build.' 

But if the faulty valve can be fixed, mission controllers will be hopeful of getting at least a brief period of calm weather in the two-hour launch window within which they can launch the rocket.  

High winds twice halted this morning's countdown with less than four minutes remaining. 

'A wind gust will put aerodynamic loads on the rocket which if big enough could push it off course or even crash,' Dr Jon Marchant, an astrophysics at Liverpool John Moores University told MailOnline.

'So the engines angle automatically to change the thrust angle to compensate. It's a bit like balancing a broom on your finger, you make constant corrections to keep the broom balanced,' 

'Obviously too big a gust will be beyond the capabilities of this 'engine-angling' (correct term is 'gimballing') to compensate and it'll crash.' 

Then a valve in the unmanned Delta IV rocket malfunctioned at the three-minute mark. Launch controllers scrambled to check all of these so-called 'fill and drain' valves in the three first-stage booster engines, but time ran out.

The valves control the flow of the liquid oxygen and liquid hydrogen in the three first-stage booster engines. The propellants combine to ignite with the explosive force needed to thrust the rocket toward space. 

Today's mission is unmanned, but in the future Nasa hopes to use Orion to put astronauts back on the moon by 2020 and take them to Mars in the 2030s

Ambition: The earliest Orion might carry passengers is 2021; a mission to an asteroid is on the space agency's radar sometime in the 2020s and Mars, the grand prize, in the 2030s

If the launch is successful tomorrow, this will be the first mission since the Apollo moon landings to take a spacecraft built for manned flight into deep space, beyond the limit of orbiting satellites. 

Orion is being developed alongside the world's most powerful rocket, the Space Launch System (SLS), which is due to make its maiden launch in 2018 or 2019.

Together, SLS and Orion will allow Nasa to send humans into deep space to destinations such as Mars.

For this launch, Orion has been strapped to a Delta IV-Heavy rocket - currently the largest launch system in the world. Three RS-68 engines will produce about two million pounds of thrust at lift-off.

Five and a half minutes after launch, at an altitude of around 200 miles (320km), fuel will have run out on both the Delta IV's main and booster engines.

A couple of seconds later, the entire bottom end - or the 'first stage' of the rocket - will detach, while the second stage engine will ignite to take Orion to a higher orbit.

The upper stage's protective fairings will then be jettisoned, along with the launch abort system, which is designed to protect the astronauts in the case of an emergency during launch by carrying the capsule to safety.

After two hours, and one orbit of Earth, the second-stage rocket will be ignited again, moving Orion up to an altitude of 3,600 miles (5,800 km).

This is 15 times the distance to the ISS and will cause Orion to travel through the high-radiation Van Allen Belts.

At three hours after lift-off, Orion will hit its peak altitude and then slowly start its descent back to Earth

The flight program has been loaded into Orion's computers well in advance, allowing the spacecraft to fly essentially on autopilot.

It should give engineers the opportunity to check the performance of Orion's critical heat shield, which is likely to experience temperatures in excess of 2,000ºC (4,000°F).

Its re-entry speed into the atmosphere will be close to 20,000mph (32,000km/h) - similar to the speed of the Apollo capsules that returned from the moon in the 1960s and 1970s.

The dry run, if all goes well, will end with a Pacific splashdown off Mexico's Baja coast and Navy ships will recover the capsule for future use.

The spacecraft is rigged with 1,200 sensors to gauge everything from heat to vibration to radiation.

Programme manager Mark Geyer said: 'We're going to test the riskiest parts of the mission. Ascent, entry and things like fairing separations, Launch Abort System jettison, the parachute, plus the navigation and guidance - all those things are going to be tested.

'Plus, we'll fly into deep space and test the radiation effects on those systems.'

A crucial test will come when Orion flies through the Van Allen belts, which are two layers of charged particles orbiting around Earth.

'The ISS would not have to deal with radiation but we will, and so will every vehicle that goes to the moon,' Geyer told the BBC.

'That's a big issue for the computers. These processors that are now so small - they're great for speed but they're more susceptible to radiation.

'That's something we have to design for and see how it all behaves.'

Another key test will be on the heat shield on Orion's base, designed to protect the craft from the searing temperatures of atmospheric re-entry.

It is 16.5ft (five metres) across and is the biggest, most advanced of its kind ever made.

Test flight: Orion will make two big laps around Earth before re-entering the atmosphere at 20,000 mph (32,200 km/h). Pictured is an artist's impression of the Orion craft in orbit

On this flight, Orion will reach close to 2,000ºC (4,000°F), not quite the 2,800ºC (5,000ºF) that was generated from the moon missions, but close enough for a good test of the technology.

That's why Orion will aim for a 3,600 miles (5,800 km) peak altitude to pick up enough speed to come back fast and hot with this mission, officially called Exploration Flight Test 1 (EFT-1).

Even though bears a strong resemblance to the Apollo command module that carried astronauts to the moon in the 1960s, it is bristling with the latest technology that makes it markedly different.

'There's an obvious comparison to draw between this first Orion launch and the first unmanned flight of the Apollo spacecraft on Apollo 4 [in 1967], but there are more differences than similarities,' space historian Amy Teitel told MailOnline.

'Apollo 4 flew a nearly lunar-ready command and service module, was the first flight of the Saturn V rocket, and demonstrated that both the S-IVB rocket stage and the spacecraft's own engine could ignite in a vacuum.

'The EFT-1 flight is only testing a spacecraft; it doesn't even have its service module!

'With Apollo 4, we knew we were going to the moon and it was clear this mission was putting us firmly back on that path after the major setback of the Apollo 1 fire. With Orion, we don't have a clear goal and a firm timeline for this new spacecraft.'

But at 11ft (3.6 metres) tall with a 16.5ft (5 metres) base, Orion is much larger than the old-time Apollo capsules, and is designed to carry four astronauts rather than three.

The earliest Orion might carry passengers is 2021; a mission to an asteroid is on the space agency's radar sometime in the 2020s and Mars, the grand prize, in the 2030s.

'We're approaching this as pioneers,' said William Hill of Nasa's exploration systems development office.

'We're going out to stay eventually. ... It's many, many decades away, but that's our intent.'

However, Nasa has yet to develop the technology to carry out manned surface operations on Mars. 

By comparison, it took eight years from the time President John Kennedy announced his intentions of landing a man on the moon - before John Glenn even became the first American to orbit Earth - to Neil Armstrong and Buzz Aldrin's lunar bootprints in 1969.

Given the present budget situation, 'it is what it is,' said Kennedy Space Center's director Robert Cabana, a former astronaut. And the presidential election ahead could bring further delays and uncertainties.

Lockheed Martin is handling the £236 million ($370 million) test flight, and Nasa will be overseeing its operation.

Nasa's last trip beyond low-Earth orbit in a vessel built for people was Apollo 17 in December 1972.

'This is just the first of what will be a long line of exploration missions beyond low Earth orbit,' said Bill Hill, deputy associate administrator for Exploration Systems Development.

'In a few years we will be sending our astronauts to destinations humans have never experienced. It's thrilling to be a part of the journey now, at the beginning.'

 


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