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J-2X engine  (Source:
NASA plans to test the J-2X engine throughout the rest of this year

NASA announced that its next-generation J-2X engine will begin its second round of tests starting today.

The J-2X engine is a redesign of the J-2 engine that carried astronauts to the moon during the 1960s and 1970s. It was developed by Pratt and Whitney Rocketdyne, which were awarded a $1.2 billion NASA contract.

The J-2X is the first new liquid oxygen and liquid hydrogen rocket engine made in 40 years that will be able to send humans into space again. In fact, the J-2X engine is designed to power deep space missions and will be used for NASA's Space Launch System (SLS), which is a heavy-lift rocket intended for deep space missions.

Last year, NASA conducted the first round of testing on the J-2X engine, which resulted in successful test firings. In that particular round of sea-level tests, the J-2X engine was fired 10 times total for 1,040 seconds, reaching 100 percent power in just four tests. It also met a full flight-duration firing of 500 seconds in the eighth test, which proved to be quicker than any other U.S. engine.

Now, the J-2X is on to its second round of testing starting today. NASA will now simulate high-altitude conditions where there is lower atmospheric pressure. According to Tom Byrd, J-2X engine lead from NASA's Marshall Space Flight Center in Huntsville, Alabama, J-2X engines will be tested in the SLS' second stage of flight where nozzle data and overall performance will be monitored.

"We're making steady and tangible progress on our new heavy-lift rocket that will launch astronauts on journeys to destinations farther in our solar system," said Charles Bolden, NASA administrator. "As we continue test firings of the J-2X engine and a myriad of other work to open the next great chapter of exploration, we're demonstrating our commitment right now to America's continued leadership in space."

The United States' role in space has been a hot topic since NASA retired its space shuttle fleet last year. Since that retirement, American astronauts have been forced to depend on Russian Soyuz rockets to make their way to the International Space Station (ISS), where the cost of one seat on the Russian spacecraft is expected to increase to $63 million by 2015. The U.S. knew it had to find another way to the ISS without depending on Russia, so it jumped on the private space travel industry to fill in the gap.

SpaceX, which is expected to be the first private company to send a spacecraft to the ISS on May 7, stepped up with its Dragon cargo capsule in an attempt to fill the void of the space shuttle fleet.

With the U.S. back in the space race, NASA plans to test the J-2X engine throughout the rest of this year. The engine is currently on the A-2 Test Stand at NASA's Stennis Space Center in Mississippi.

Source: NASA

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RE: Yawn...
By geddarkstorm on 4/25/2012 8:32:07 PM , Rating: 3
Short of putting a fully functional nuclear reactor on board, there's no way to even remotely power an ion engine at the levels needed to give thrust comparable to a chemical rocket.

The laws of physics (action creates opposite equal reaction) are just too stubborn to be bent quite yet.

In short, sorry, for leaving a gravity well starting at sea level, there's nothing, not even theoretically on the drawing board, that can accomplish that except a chemical rocket.

RE: Yawn...
By Fritzr on 4/25/2012 10:30:06 PM , Rating: 2
A space elevator (aka Beanstalk) would get the ion engine out of the gravity well.

Designs exist, but construction schedule is still in the "we're thinking about doing it someday" stage.

Laser boost is in the X-craft phase and may one day be capable of getting an ion engine out of the gravity well.

Chem engines will never be obsolete though. They will be required for entering and leaving gravity wells which do not have a launch infrastructure in place.

Atomic rockets likely could be used to enter/exit a gravity well, but safety concerns will prevent that usage.

RE: Yawn...
By geddarkstorm on 4/26/2012 12:38:12 AM , Rating: 2
No way a laser can give the thrust capacity of a chemical rocket. The amount of energy needed would destroy whatever you're lasering at. Laser ideas are for small course adjustments for craft already in space.

A space elevator is a fun idea but... one has to consider the stress from the planet's rotation (things in orbit are moving VERY FAST compared to things on the ground, how do you account for that while elevating up? You'd have to accelerate sideways as you elevate or you'd slow down the space based tether and drop it into the atmosphere, not to mention the sheer stress is enormous; it'd use more fuel than just rocketing up conventionally), weather patterns (what happens if a hurricane or tornado hits it, or an earthquake at the earth side tether point?), electrical effects (so much ionization in the upper atmosphere, and now you've given it a convenient path to get to the ground), temperature differentials (if it's 80F on the ground and -150F in the mesosphere, and 2,700F (though not practically, just theoretically) in the thermosphere where the ISS is, what is that going to do to your materials since heat can now flow through it and conduct? Expansion, contraction? Effects on material defects and microfractures? Light versus Night?), space/atmosphere debris (animals) and meteors (the elevator is an immobile target; vanishingly small, as space scales go, but still a sitting duck that can't maneuver much out of the way of danger), and of course gravity itself (how heavy would something dense enough to support the elevating weight you're moving into space have to be, and how would that ever have the strength to survive the material stress of gravity?).

How would you move over a ton of cargo weight as rockets can lift with these issues? It isn't ever going to happen with our current physical law constraints (maybe we'll find a new law and be able to circumvent it).

RE: Yawn...
By futrtrubl on 4/26/2012 5:08:10 AM , Rating: 2
Are you thinking of laser propulsions systems that reflect the laser to impart momentum? If so then sure they'll never get there for your reasons. But there are other methods for using lasers for propulsion. There's the use of microwave lasers to create plasma that can be electrodynamically accelerated to give thrust. Hell you could shoot a powerful laser at an ablative target within a nozzle to give thrust BY the destruction you mentioned.

Yes as a mass travels up a tether the counter weight mass would become retarded, however if the counterbalance is oversized correctly this would cause the net force on the mass to no longer be vertical and would tend to right the system (potentially with oscillation which is a problem) little fuel needed. If there is cargo transfer earthbound (there's little point in industry in space if goods don't come back to a human market) they can be scheduled to effectively negate each other.

Hurricanes and tornadoes can cause issues but the thickness of a tether at the Earth's surface is not that great.

Regarding earthquakes, sure they can strike randomly and do significant damage but you can mitigate that danger by selecting low risk sites and at worst if the cable detaches at the Earth's surface it drifts up, how much depends on the counterbalancing, and then it's a matter of repositioning it to reattach it, something that would have had to have been solved to install the tether in the first place.

Debris strikes can my mitigated by redundancy and ability to repair sections. Animal strikes.... I doubt a bird strike will do much to a cable capable of of suspending multi-tonne loads. The counterbalance itself is not much of a sitting target itself, it can raise and lower its orbit, retard and advance it. Considering the mass required it would be a captured comet or asteroid itself and most of that would be shielding for an structures so only large debris would be an issue which are easier to track and avoid.

It's not how dense the cable needs to be it's how strong/density the cable material needs to be and it's already been calculated how strong it needs to be. For a non-tapered cable (a worst case cable profile) carbon nanotube and graphene cables are both theoretically strong enough, it's just scaling it up is the issue. So no laws of physics need to be rewritten.

RE: Yawn...
By Gondor on 4/26/2012 5:33:51 AM , Rating: 3
RE: Yawn...
By JediJeb on 4/26/2012 9:13:18 PM , Rating: 2
No way a laser can give the thrust capacity of a chemical rocket.

Where the space elevator is concerned the laser is used to beam power to the climbing elevator carriage. You shine the laser up to a photocell which allows you a way to get electricity to the carriage without the weight of batteries, generator or power cable adding weight to the assembly.

You can find quite a bit of information on where the technology is currently at this site:

They are even running an XPrize type contest looking for different components.

RE: Yawn...
By voronwe on 4/28/2012 12:03:26 PM , Rating: 2
All of these potential problems were sorted out decades ago. There are several good books on the topic, and lots of websites.

The only real remaining obstacle has been the power beam engineering and the wait for roll-to-roll graphene to go into mass production, or roll-to-roll carbon nanotubes. Graphene is already roll-to-roll; you can now go out and buy a single molecule of infinite length if you have the money. Nanotubes are proving very difficult to produce in the lengths required, but considering the value of the material (much more conductive than copper, much stronger than steel) it will probably happen some day soon.

Then it's strictly an engineering and funding problem. And it's not that expensive.

"And boy have we patented it!" -- Steve Jobs, Macworld 2007

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