New Kind of Orbit Could Ease Mars Communications 127
japan_dan writes "An interesting way to enable Earth-Mars communication when the Sun occludes the direct radio line-of-sight: ESA proposes placing a pair of continuous-thrusting relay satellites, using a solar electric propulsion system — one in front and ahead of Mars, the other behind and below — with both following non-Keplerian, so-called 'B-orbits'. This means the direction of thrust is perpendicular to the satellites' direction of flight, allowing them to 'hover' with both Earth and Mars in view. Quoting from the Q&A: 'We found that a pair of relay satellites would only have to switch on their thrusters for about 90 days out of every 2.13-year period, and this solution would only increase the one-way signal travel time by one minute, so it could be effective.'" Here is the paper describing non-Keplerian orbits (PDF).
Re:lets wake up here (Score:5, Insightful)
The only reason private enterprise is able to *think about* real space travel is because they are using the ~40 years of NASA knowledge and research.
http://science.howstuffworks.com/ten-nasa-inventions.htm [howstuffworks.com]
Ok so this is really basic, but also aerogel, and a laundry list of other things.
Being on Mars is really cool, and we have learned a lot about it. But as for usefulness it tells us maybe mining Mars wouldn't be that profitable (but did we know that before). But all the stuff they used to get to Mars, that shit trickels down FAST. I mean I personally believe that SSDs on the rovers are wat put them into the main stream. They lasted in a super harsh enviroment orders of magnitude longer than they were supposed to. So keep thinking all NASA produces is cool photos.
Re:Wouldn't it make more sense.... (Score:4, Insightful)
Also, to be pedantic, you would still need some fuel on a LaGrange spacecraft for station-keeping purposes. Though this amount would be minimal, you can't justifiably claim that you wouldn't need *ANY* fuel.
Cheers Mate.
Re:lets wake up here (Score:1, Insightful)
You speak sense, but if you come to slashdot and piss on the sci-fi nerds' fantasies of colonizing the universe within the next hundred years, you're doomed to be buried in flames. Mostly what you'll see is people terribly excited about frontier-style colonization efforts or admitting that our current space efforts make little sense but justifying them because it's good practice for our engineers. It's too early for colonization (we're not even close) and the "good practice" justification is just nonsense, but for some reason those are the most popular arguments.
AC so that only one of us goes down in flames =)
Bandwidth (Score:5, Insightful)
This is slightly tangential, but worth noting I think:
This will be handy when we can't afford to lose contact with Mars for even a few days, but there's a bigger problem lurking in inter-planetary communications: bandwidth. We don't really have enough Deep Space Network dishes (particularly, the large 70-m ones) to talk to all of our missions as much as we should. We're sacrificing data collection on billion-dollar missions on a daily basis on the grounds that we don't have enough bandwidth to get it back. When we put people or even just more missions on Mars, that'll only get worse.
Re:lets wake up here (Score:5, Insightful)
What are you doing at a nerd site? Money is the LAST thing a nerd is thinking of when (s)he thinks of space. Space is for technological and scientific advancement. Sue, there will be money made in the future, but private enterprise operates on the next fiscal quarter.
NASA is doing ot because (duh) THERE'S NO MONEY IN SPACE EXPLORATION and money is the only reason for private enterprise to even exist.
For those who don't RTFA (Score:4, Insightful)
To clarify - this sort of "orbital" motion (not really "orbital" since it actively powered) is hardly a new idea. What is relatively new is the fact that you have engines that permit you do do it without prohibitive fuel consumption. It's different from a hovering rocket-propelled lander (like the DC-X) only in scale. The key feature, not clear in the article, is that you are intentionally thrusting along the local vertical, in the direction of gravity, to modify its effects. That was possible and everybody knew about it since, well, Newton figured out gravity. What we haven't been able to do is to maintain it for more than the briefest periods due to excess fuel consumption.
The new part here is the Hall Current thruster, which is ~factor of 10 more efficient than traditional engines. The specific impulse of these is around 1800 seconds (lb-sec of impulse per lbm of fuel- hey I didn't invent the units, I just use them...) compared to maybe 180 for a hydrazine monopropellant thruster. These are not exactly "new" either, the Russkies have been using them for decades. Only recently has the western world begun to develop them, so it's new only in that sense. So the solution they are looking at is now looking reasonably practical, although no doubt still significantly limited by the fuel consumption.
Brett
Re:Eh? (Score:3, Insightful)
Yup, prolly should have been "in front and above".
Re:Cita tion need ed (Score:3, Insightful)
Re:How about.... (Score:3, Insightful)
Re:lets wake up here (Score:3, Insightful)
Since there's barely anything useful on the Moon given the cost of getting it, and there's even LESS useful on Mars
Since you know the exact chemical composition of the entirety of the moon and Mars, would you mind sharing with the rest of us?
Re:Wouldn't it make more sense.... (Score:3, Insightful)
Re:For those who don't RTFA (Score:5, Insightful)
Hey, ISP is in seconds, it's an industry standard.
But it shouldn't be. N*s/kg is the correct unit for specific impulse. "Seconds" is only used by American engineers who don't understand the difference between weight and mass.
When I was a kid I was deeply interested in space, but it wasn't until years later that I understood the meaning of Isp because of the idiotic convention of designating it in seconds, rather than force*time/mass, which makes its meaning completely obvious.
If you want to turn people off an understanding of the most basic aspects of space travel, by all means go ahead and keep using seconds for Isp. But it's really time for the United States to get with the rest of the world and abandon Imperial units, although I guess as an imperial power they seem like a natural fit.
[Ok, now wondering if this'll get more "troll" or "flamebait" mods. It should probably lean toward "flamebait", as the story is true: Isp in seconds really did confuse me for years. The egregious America-bashing is, well, egregious, so probably warrants a flamebait mod. But really, what's with the Imperial units, kids?]