The thread for space cadets!

[peter grimes]

FunFact: The gyro sphere in the Gravity Probe experiments are the most spherical objects made so far. If earth were smoothed to their precision the Everest would rise about 1 meter above sea level. Engineering is truly awesome.

 

[uppi]

You are making two assumptions:
1) That the asteroid is passing close to the moon
2) The orbital path we see is in large part due to the moon's influence.

No, it is the other way around. I am not making these assumptions. And I agree that cannot make them. Those are my conclusions from the (projection of) trajectory of the asteroid.

I'm saying we can't say either are the case without a better perspective and actually doing the orbital equations. You can say two-body this, three body that, but it's an empty claim without actually doing the equations. The presented video misses the entire third dimension, which can royally screw with us and mislead what we think we see. You also earlier stated that the orbits look planar - which is another bad assumption. Not to beat up on you, but it's actually a terrible assumption because that asteroid can come in at angle to earth's orbital plane but from a 2-d perspective, it looks planar because in 2-d it is.

The projection in 2-D gives me the full information about the angular momentum of the asteroid with respect to the earth along the direction perpendicular to the imaged plane. The contribution of any motion in the third dimension contributes exactly nothing to that. That angular momentum has to be conserved. And it is easy to see without doing any calculations that it is not conserved in the earth-asteroid system. So there has to be a third body to preserve angular momentum. I am guessing that this is the moon and my conclusions follow from that. I know very well, that it is a terrible assumption for the orbits to be planar. That's why I am not assuming it at all. It is my last conclusion after the other conclusions.

The third dimension can screw with our perception, but it can not alter the fundamental symmetries of nature, which would be violated if there was no third body involved in that trajectory.

One other thing, even in a two body system, if you simplify the earth as a perfectly flat sphere, then you can draw some conclusions on how the asteroid would act. But that's another bad simplification as the lumpiness and squashed nature of the earth significantly effect orbital trajectories.

Close to the Earth those deviations from a perfect sphere play a role. But that asteroid never comes that close to the earth (and any motion in the third dimension would put it even further away from the earth). That far out, you can treat the Earth as a point-like particle and still get reasonable results. There might be tiny corrections to that, but unless you get close to the surface (like when launching something) nothing major.

 

[hobbsyoyo]

The projection in 2-D gives me the full information about the angular momentum of the asteroid with respect to the earth along the direction perpendicular to the imaged plane.

Say what?

 

[uppi]

Say what?

Let's say the plane we see is along the x- and y-direction and the third direction is the z-direction. Because of the 2-d image we have no information about the z-direction.

The angular momentum is defined as:
L = r x m*v
(bolded symbols are vectors)

When I want to calculate the z component of the angular momentum L, the properties of the cross product tell me that I only need to consider the x and y components of r (the position of the asteroid) and v (the velocity of the asteroid). All of these I can extract from the image, so I can fully determine the z component of L, and this quantity needs to be conserved.

 

[LamaGT]

Say what?

What he means is that from that 2D gif we can still see how it did a few orbits before being ejected, meaning that something took the energy away and that something is the moon.

 

[MagisterCultuum]

FunFact: The gyro sphere in the Gravity Probe experiments are the most spherical objects made so far. If earth were smoothed to their precision the Everest would rise about 1 meter above sea level. Engineering is truly awesome.

I thought this was the more spherical object:

Link to video.

This sphere was made as round as possible out of a single isotope of silicon as part of an attempt to better define such constants as Avagadro's Number and the mass in a kilogram.

Edit: At the bottom of the video description it says that there is a debate as to whether this or gravity probe b rotors are rounder.

 

[hobbsyoyo]

uppi

Do not shame me with equations from last week's homework!!!!

 

[peter grimes]

I thought this was the more spherical object:

Link to video.

This sphere was made as round as possible out of a single isotope of silicon as part of an attempt to better define such constants as Avagadro's Number and the mass in a kilogram.

You could be correct, I'm just repeating what I heard. So I did a quick google search - none of the results of the first page mentioned manmade objects other than Gravity Probe B.

https://startpage.com/do/search?query=most+spherical+object&cat=web&pl=chrome&language=english

 

[PlutonianEmpire]

Yes, but Isn't the sun even rounder than all of this?

 

[uppi]

Yes, but Isn't the sun even rounder than all of this?

No

http://science1.nasa.gov/science-news/science-at-nasa/2008/02oct_oblatesun/

gives the deviations from a sphere as 6km on a 700000km radius, that is a factor of 10^-5. With the silicon spheres 50nm deviations on a radius of 50mm has been achieved, that is a factor of 10^-6. So they're an order of magnitude rounder than the sun.

 

[hobbsyoyo]

Alright, since no one wants me to write up a brief history of the Soviet Moon program, sad enjoy this movie about it instead:

Link to video.
It's pretty awesome and it also talks a bit about the differences between American and Soviet engines. Although I do have to say that the analysis that Winner offered that Russian engines are better than Western ones is a pretty incomplete assessment as it leaves out a lot of the history of how that came to be and ignores recent developments, it's not an altogether false assessment.

It was either this movie or another documentary where one Russian engineer states that the Soviet people weren't told about Apollo moon landings until many years later and I was like :whoa:.

There's another great documentary called Red Star in Orbit and it's a pretty awesome documentary about the history of the Soviet Space Program. It was shot in 88-89 or so, just when they were beginning to open up their closet of secrets. At one point, an engineer is talking about a massive failure of their program and starts to stop himself, then goes, "Well, Glasnost is Glasnost so I can tell you now" and then finishes his story. I don't know why but I found that really interesting, to peer back in time to the very moment when that system both opened up and then broke apart. Or maybe that scene was in the other documentary. Can't remember. Oh and at one point they talk about how a ship was sent to resupply Mir and when the Cosmonauts opened it, it was empty. The Kazakhi technicians who worked at Baikonaur had raided the capsule and stolen the food to feed their families because after the USSR broke up they stopped getting paid.

Anywho, here's part one of three of the Red Star in Orbit.

Link to video.

 

[hobbsyoyo]

Another excellent documentary: NUKES IN SPACE!!!!!


Link to video.
William Shatner narrates. This movie is very similar to the documentary The Atomic Bomb Movie, also narrated by Shatner and also super-awesome.

 

[hobbsyoyo]

It's pretty awesome and it also talks a bit about the differences between American and Soviet engines. Although I do have to say that the analysis that Winner offered that Russian engines are better than Western ones is a pretty incomplete assessment as it leaves out a lot of the history of how that came to be and ignores recent developments, it's not an altogether false assessment.

To elaborate on this, one of the principle reasons the Russians had to develop such massive engines (and launchers) is that they were unable to successfully miniaturize their nuclear warheads until a long time after the Americans. By the time ICBM systems began to develop (such as the R-7, which became the Soyuz launcher or the Atlas ICBM that lofted Mercury astronauts and still launches satellites) the Americans had been able to bring down the size of the earliest atomic bombs down to a reasonable mass and size. The Soviets still hadn't been able to do that, so it was necessary to develop enormous rockets from the get-go such as the R-7 to do the same job a smaller rocket like the Atlas could do with it's smaller payload.

From that starting point the two programs differed considerably. The Russians were also unable to create successfully Lox/H2 engines because they couldn't overcome the difficulty of storing liquid H2. You can see how this affected their rockets by comparing the N-1 moon rocket with it's Saturn V counterpart. The N-1 used Kerosene-burning engines on it's upper stages, which is a much less efficient propellant than H2. So they had to carry more fuel in those upper stages to do the same job (actually, to less of the same job - the N-1 carried less payload than the Saturn V). To loft that extra payload into orbit, they needed a bigger first stage and so the N-1 had I think 33 NK-15 engines in it's first stage, which produced higher thrust to loft the heavier rocket with less payload off the ground.

And while the first stage of the Saturn V was itself enormous, it was smaller (mass wise) than the N-1, and because of the efficient H2 fueled engines of the upper stages, could deliver an even bigger payload than the bigger N-1 rocket.

The Russians, to date, still haven't utilized H2 engines on their launchers (though the mythical Anagar rocket will use it IIRC). So they needed bigger engines to overcome the inefficiencies of the fuels that they use that necessitated bringing more fuel along.

That, factored in with the Russian strive to make everything as rugged and as simple as possible, led to the creation of some truly fantastic engines (when they worked). They had a lot of teething problems along the way; the NK-15 engines for the N-1 were never reliable, for example. They lead directly or indirectly to the destruction of all four N-1 test launches and with it the Soviet lunar landing program. However, after much trial and error, the NK-15's turned into the NK-33's, which are highly reliable and fantastically efficient despite not using H2. But by the time they came out, they had no use as the Soviet program had cancelled the lunar landing. In fact, the developer of the NK-33 was ordered to destroy all of the engines they had produced already. The developing bureau instead chose to say they were destroyed but in fact stored them in a Moscow warehouse where they sat for nearly 30 years. Then the USSR collapsed and the bureau began selling them to the US for use on Atlas launchers and the new Antares rocket. It's funny how it all came full circle!

Oh and the other big breakthrough that the Russians pioneered was the closed-cycle combustion process which they perfected on the NK-33's. A rocket engine has lots of turbopumps and turbomachinery that feed it propellant and to power this machinery, the engine has a separate combustion chamber where a bit of oxidizer and propellant are burned. Typically, the byproduct gases of this process are dumped overboard and either create no thrust or very little if the outlets are made into mini-nozzles themselves. Either way, a lot of propellant is wasted in this method.

To create an even more efficient engine, you could take the byproduct gases from the turbopump combustion chamber and pump it into the main combustion chamber and out of the nozzle so that it isn't wasted. The problem is that trying to pipe hot, high pressure gas into an even hotter, higher pressure vessel is an engineering nightmare. Particularly because often that byproduct is either 'oxygen-rich' or 'fuel-rich'; extra quantities of either the oxygen or the fuel are pumped into the turbopump combustion chamber to help control the burn, but that extra quantity is itself not burned. When you then try and pump around this fuel or oxygen-rich mix, it tends to want to react as it's now hot and pressurized but not burnt into inert products. So it eats away at all of the pipes and machinery as it travels around, particularly if it's an oxygen-rich mix.

What the Russians were able to do in the NK-33 was create special steel alloys that could handle this hot, reactive gas as it traveled around then engine and eventually made it's way into the main combustion chamber where it was burnt off and produced useful thrust.

To my knowledge, however, the closed-cycle wasn't used on any other Russian engines. I could very well be wrong on that however. In any case, it was a breakthrough but the extra challenges of doing closed-cycle make an engine more complex, more expensive, less reliable and so on. So most firms haven't used it as the extra efficiency isn't seen as worth it I guess.

So in the end, the Russians developed big, powerful and simple engines while the Americans tended to go for smaller, more complicated and efficient designs. You could argue either way about who makes better engines and up until this decade I'd probably side with the Russians. However, recent developments have shown that the Russians have lost a handle on quality-control and as such have lost a lot of that 'edge' in engine design. Just as importantly, the Russians seemed to have stalled out on innovation, to my knowledge, they haven't developed any new engines of note since the collapse of the USSR and are at this point just producing the same old designs. And there's certainly a lot to be said with sticking with things that work - witness the loss of capability as the US switched from Saturn V to Space Shuttle, for example. But on the other hand, firms like Lockheed (which developed new, powerful and simple H2 engines for the Delta IV) or SpaceX (which developed the highest thrust-to-weight engine ever produced, the Merlin) continue to push rocket science forward and in new directions. Meanwhile, the Russians stick to tried-and-true and fail at it.


Link to video.
Watch that blast wave shake everyone after impact!

_______________________________

A 'wow moment': Curiosity finds water on Mars as common as dirt

Future Mars explorers may be able to get all the water they need out of the red dirt beneath their boots, a new study suggests.

NASA's Mars rover Curiosity has found that surface soil on the Red Planet contains about 2 percent water by weight. That means astronaut pioneers could extract roughly 2 pints (1 liter) of water out of every cubic foot (0.03 cubic meters) of Martian dirt they dig up, said study lead author Laurie Leshin, of Rensselaer Polytechnic Institute in Troy, N.Y.

"For me, that was a big 'wow' moment," Leshin told Space.com. "I was really happy when we saw that there's easily accessible water here in the dirt beneath your feet. And it's probably true anywhere you go on Mars." [The Search for Water on Mars (Photos)]

The new study is one of five papers published in the journal Science Thursday that report what researchers have learned about Martian surface materials from the work Curiosity did during its first 100 days on the Red Planet.

Soaking up atmospheric water
Curiosity touched down inside Mars' huge Gale Crater in August 2012, kicking off a planned two-year surface mission to determine if the Red Planet could ever have supported microbial life. It achieved that goal in March, when it found that a spot near its landing site called Yellowknife Bay was indeed habitable billions of years ago.

But Curiosity did quite a bit of science work before getting to Yellowknife Bay. Leshin and her colleagues looked at the results of Curiosity's first extensive Mars soil analyses, which the 1-ton rover performed on dirt that it scooped up at a sandy site called Rocknest in November 2012.

Using its Sample Analysis at Mars instrument, or SAM, Curiosity heated this dirt to a temperature of 1,535 degrees Fahrenheit (835 degrees Celsius), and then identified the gases that boiled off. SAM saw significant amounts of carbon dioxide, oxygen and sulfur compounds — and lots of water on Mars.

SAM also determined that the soil water is rich in deuterium, a "heavy" isotope of hydrogen that contains one neutron and one proton (as opposed to "normal" hydrogen atoms, which have no neutrons). The water in Mars' thin air sports a similar deuterium ratio, Leshin said.

"That tells us that the dirt is acting like a bit of a sponge and absorbing water from the atmosphere," she said.

Some bad news for manned exploration
SAM detected some organic compounds in the Rocknest sample as well — carbon-containing chemicals that are the building blocks of life here on Earth. But as mission scientists reported late last year, these are simple, chlorinated organics that likely have nothing to do with Martian life.

Instead, Leshin said, they were probably produced when organics that hitched a ride from Earth reacted with chlorine atoms released by a toxic chemical in the sample called perchlorate.

Perchlorate is known to exist in Martian dirt; NASA's Phoenix lander spotted it near the planet's north pole in 2008. Curiosity has now found evidence of it near the equator, suggesting that the chemical is common across the planet. (Indeed, observations by a variety of robotic Mars explorers indicate that Red Planet dirt is likely similar from place to place, distributed in a global layer across the surface, Leshin said.)

The presence of perchlorate is a challenge that architects of future manned Mars missions will have to overcome, Leshin said.

"Perchlorate is not good for people. We have to figure out, if humans are going to come into contact with the soil, how to deal with that," she said.

"That's the reason we send robotic explorers before we send humans — to try to really understand both the opportunities and the good stuff, and the challenges we need to work through," Leshin added.

For example, Curiosity's laser-firing ChemCam instrument found a strong hydrogen signal in fine-grained Martian soils along the rover's route, reinforcing the SAM data and further suggesting that water is common in dirt across the planet (since such fine soils are globally distributed).

Another study reveals more intriguing details about a rock Curiosity studied in October 2012. This stone — which scientists dubbed "Jake Matijevic" in honor of a mission team member who died two weeks after the rover touched down — is a type of volcanic rock never before seen on Mars.

However, rocks similar to Jake Matijevic are commonly observed here on Earth, especially on oceanic islands and in rifts where the planet's crust is thinning out.

"Of all the Martian rocks, this one is the most Earth-like. It's kind of amazing," said Curiosity lead scientist John Grotzinger, a geologist at the California Institute of Technology in Pasadena. "What it indicates is that the planet is more evolved than we thought it was, more differentiated."

The five new studies showcase the diversity and scientific value of Gale Crater, Grotzinger said. They also highlight how well Curiosity's 10 science instruments have worked together, returning huge amounts of data that will keep the mission team busy for years to come.

"The amount of information that comes out of this rover just blows me away, all the time," Grotzinger told Space.com. "We're getting better at using Curiosity, and she just keeps telling us more and more. One year into the mission, we still feel like we're drinking from a fire hose."

The road to Mount Sharp
The pace of discovery could pick up even more. This past July, Curiosity left the Yellowknife Bay area and headed for Mount Sharp, which rises 3.4 miles (5.5 kilometers) into the Martian sky from Gale Crater's center.

Mount Sharp has been Curiosity's main destination since before the rover's November 2011 launch. Mission scientists want the rover to climb up through the mountain's foothills, reading the terrain's many layers along the way.

"As we go through the rock layers, we're basically looking at the history of ancient environments and how they may be changing," Grotzinger said. "So what we'll really be able to do for the first time is get a relative chronology of some substantial part of Martian history, which should be pretty cool."

Curiosity has covered about 20 percent of the planned 5.3-mile (8.5 km) trek to Mount Sharp. The rover, which is doing science work as it goes, may reach the base of the mountain around the middle of next year, Grotzinger said.

Cool pic:

 

[PlutonianEmpire]

I dunno how reputable this source is, but it seems like a good read:

http://gulfnews.com/about-gulf-news...-review/the-psychology-of-isolation-1.1235805

Since April, thousands of people have applied to take a one-way trip to Mars. Following further stages of selection and training, the plan is for the first four astronauts to lift off in 2022. After a seven-month journey they will settle permanently on the Red Planet to conduct scientific experiments and do whatever it takes to survive. Meanwhile, the rest of us will be able to watch their lives unfold on reality TV.

The Mars One programme is daring but is it realistic? Nasa is sceptical about a private one-way mission and instead plans to send more rovers followed by a manned return mission sometime in the 2030s. Others have questioned Mars One’s business model, technical feasibility and the health risks posed by radiation.

On top of these concerns, Martian colonists will face extreme psychological conditions. Mars One claims to have discussed their plans “with experienced and respected psychologists” but doesn’t name them or refer to any supporting evidence. At the same time they have called for applicants who are resilient, adaptable, curious, trusting, and creative but without saying why these particular traits are the most important, how they will be measured, or how the standards for selection will be set. Even Professor Raye Kass, who appears to be one of their few advisers on mental health issues, offers little more than anecdotes as evidence for the psychological feasibility of the programme.

Existing research suggests that the colonists will face at least four major psychological challenges. Individually, each of these is serious enough to raise a red flag. In combination, they are a disaster waiting to happen.

I won't be quoting the rest, so you have to get off your lazy bums and click the link to see.

Spoiler My take on it :

My take on it is that sometimes, it seems like manned space exploration is being deliberately sabotaged with projects purposefully designed to fail. Then again, that's the conspiracy theorist in me.

 

[Borachio]

Hmm. I wouldn't have thought this is a reputable source at all.

The Mars One colonists will be the most isolated humans to have ever lived. Because of their distance from Earth, real time interaction with people back home will be impossible — the shortest delay for sending transmissions will be about 10 minutes. For the rest of their lives they will be able to interact directly with only their fellow colonists, who will increase from three people in the first two years to 23 people after 10 years.


These circumstances will probably cause mental illness in at least some of the colonists. Decades of research shows that prolonged social isolation in astronauts can lead to depression, insomnia, anxiety, fatigue, boredom, and emotional instability. Mars One believes that selecting applicants with the right attitude will help prevent such problems. As Kass puts it: “It all starts with attitude. Think of it. When a person finds herself, or himself, on Mars, with no way of being able to come home, and potentially questioning the decision that they have made, what is going to ground them in the choice they have made?”

This just looks like some random blogger to me. Though I'm not saying it doesn't raise some of the relevant issues.

 

[peter grimes]

Cool pic:

I was going to ask you which object this is, but quoting this post has shown me the answer. I got it wrong.

 

[LamaGT]

Does NASA have any serious project that is tackling with the task of sending humans to Mars? As I understand the SLS is one of the key requirements but what then? 2030 seems such a random date, I'm pretty sure it can be done faster.

 

[hobbsyoyo]

Does NASA have any serious project that is tackling with the task of sending humans to Mars? As I understand the SLS is one of the key requirements but what then? 2030 seems such a random date, I'm pretty sure it can be done faster.

That depends on how you define 'serious', but for mist definitions the answer is no.

A landing *could* be done by 2030, it is withing technical capability. But it will be far more expensive, monetarily and politically, than any current world government is willing to spend.

 

[hobbsyoyo]

Today in Space:

NASA will shut down beginning tomorrow if the Federal government shuts down. All work, excepting mission control in support of the ISS, will stop.

The Falcon 9 v1.1 successfully lifted a payload od satellites into orbit. Test to reignite the engines to slow the stages down to investigate reusability attempts were only partially successful. Elon Musk claims the problems encountered were minor and easily fixable, however.

Orbital Sciences Cygnus resupply ship successfully docked with the ISS today and delivered 700kg of cargo. Future missions under the resupply contract will carry between 2000 and 2700kg of cargo.

 

[peter grimes]

*all work* beyond ISS? that can't be true. Nasa almost certainly provides services for NRO, at the very least. No way in hell they'll stop taking pictures of stuff.