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New Proposed Path for Manned Trips to Mars: Let Mars' Gravity Capture Spacecraft
As illustrated in this article at io9.com, the conventional method considered for launching a manned craft to Mars might make less sense, even if it takes less time, than a more complicated but more efficient means akin to a method that's been already been successfully used to minimize the amount of fuel used in exploring both within and beyond the solar system.
Known as the "Hohmann Transfer" method, this type of maneuver is known to be effective. But it is also quite expensive and relies very heavily on timing. Hence why a new idea is being proposed which would involve sending the spacecraft out ahead of Mars' orbital path and then waiting for Mars to come on by and scoop it up.
This is what is known as "Ballistic Capture", a new technique proposed by Professor Francesco Topputo of the Polytechnic Institute of Milan and Edward Belbruno, a visiting associated researcher at Princeton University and former member of NASA's Jet Propulsion Laboratory.
In their research paper, which was published in arXiv Astrophysics in late October, they outlined the benefits of this method versus traditional ones. In addition to cutting fuel costs, ballistic capture would also provide some flexibility when it comes to launch windows.
Mars aint the kind of place to raise your kids
Maybe we can use this to get to other universes??
For a manned mission it is necessary to minimize time, not fuel.
When all you have is a hammer, every problem starts to look like a thumb.
Some mysteries we were never meant to have an answer to.
So, we start with the quote about a Hohmann Transfer, in such a way as to suggest something completely different.
I'm sure there was a good reason for that, though TFA itself manages to mangle a bit of orbital physics all on its own, in addition to whoever submitted/edited the /. suumary....
"I do not agree with what you say, but I will defend to the death your right to say it"
Which is it? Efficient or expensive?
If it's more efficient, e.g. costs less fuel, it should be less expensive. We've been calculating orbits that could thread a comet past Jupiter's orbit for decades now. Complexity just costs a few microseconds of computer time.
One actually requires a constrained optimization that weights both, because the minimum time method requires exponentially more fuel: to keep the rocket accelerating nonstop until it's halfway then nonstop again to decelerate.
This was my main method for landing on planets. It's pretty good.
How do I do this in Kerbal Space Program?
A National Academies of Science report, published earlier this year, indicated that people, who "might" venture to Mars have not been born, the people who "might" build the space craft and launching systems and facilities have not been born, the people who will educate and train the people who "might" build the space craft and launching systems and facilities and the people who "might venture to Mars have not been born and the national culture, economy, educational systems, infrastructure and industry do not at present exist and will not likely exist for another 50 to 100 years.
The recent Orion launch test was a One-Off funded by money from the last Bush administration. The Obama administrations have not funded any new space craft design, or even manufacturing let along funding the building of facilities for such a space craft because such a space craft does not exist.
At present and for the foreseeable future the USA will not have any capability to launch a human space mission to low-earth-orbit for another 20 years if ever.
Reality enforces gravity.
Wasn't this already addressed recently?
1) This is horrible for manned craft, due to the much longer flight-time resulting in higher costs for maintaining the crew ... uhm, I'm sure there were more points
2) This is far from new, though so far only used for getting to the moon
3)
Why is this linking to a Gawker site (IO9) instead of the actual original article at:
:(
http://www.universetoday.com/117615/making-the-trip-to-mars-cheaper-and-easier-the-case-for-ballistic-capture/
The Gawker site merely copies/pastes what the original article states plus ad LOADS of additional advertising.
How does this get past the Slashdot editors? Was this an intentional Promo or has Slashdot declined just this much these days
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I hope they tested in the proper program before the big announcement.
So obviously their definition of efficiency seems to be a little different from common definitions. Then they say it is effective but complicated. Looks they are shooting for a well diversified portfolio of adjectives,
sed -e 's/Chuck Norris/Rajnikant/g' joke > fact
Gawker sites are always useless clickbait advertising traps. Thus they have so many sites linking to each other for more advertising clicks. What passes for journalism there is simply reposting other people's work. Buzzfeed actually manages to be worse (you know it is bad when Gawker calls someone out for plagarisim.)
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Why not put all the soda and stuff on the moon and then steer the moon towards Mars?
Does someone have a patch to implement this in MechJeb? Is it time to redraw the delta-v subway map?
Current state of the art for landing on Mars has a circular error probable of 5-10 km. That's quite a distance to travel to go find all your supply drops, scattered over several hundred square km, especially given the speed at which current Mars rovers go (a few cm/second).
You have two sort of alternatives: one is an autodriving vehicle with enough robotic capability to go pick up the loads (or land all loads on a rover and have them drive to a central point). Current state of the art is tens of meters/day, limited mostly by electrical power, although also by computational horsepower to do the nav and obstacle avoidance. One could have human operators mapping out jumps of 10-30 meters from photos, but still, it's going to take months to get all that stuff collected and in one place.
Or, you can have astronauts driving a mars buggy, which can go meters/second, so you could conceivably go many km. However, the several hundred kg lunar rover had a max range with non-rechargeable batteries of about 30km, and could go a few km/hr. So it's not exactly a turnkey solution.
That said, sending multiple drops *is* probably a good way to do it, since you could standardize and potentially do a manufacturing line kind of thing to reduce recurring engineering costs. Current Mars rover/landers aren't built this way: they're individually hand crafted and quite idiosyncratic: Spirit and Opportunity were built by the same people from the same drawings at the same time, but, yet, have a lot of behavioral differences.
In fact its cold as hell
This is precisely what SpaceX is working on doing with the Dragon series spacecraft, a combination of drag and propulsive landing, no parachutes, depending on the nature of the atmosphere and local gravity
If the body has no atmosphere (i.e. the moon), it would do a purely propulsive retro-fire and landing.
On a body with a thick atmosphere (i. e. Earth), drag on the heat shield would do most of the deceleration, with a final propulsive touchdown.
Mars is a middle case, there is some atmosphere but not nearly enough to do the job. It basically has to do a propulsive descent, but the trick is the rocket is thrusting against the oncoming atmosphere, so the aerodynamics are very complicated. Recent attempts to soft land the first stage of the Falcon 9 rocket have produced some very useful experience in this flight regime.
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If it works in Kerbal Space Program, what the hell, go for it :-)
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"At the same time, sending a rocket into space, through the vast gulf that separates Earth's and Mars' orbit, and then firing thrusters in the opposite direction to slow down, requires a great deal of fuel."
The Hohmann Transfer is, mathematically provably, the *most efficient* way of travelling between any two orbits. It may require a "great deal of fuel", but that's still a great deal less than any other trajectory, which is precisely why we're willing to wait for the launch windows.
As to the rest, aerobraking and aerocapture is clearly more energy efficient. This article is like saying coal is better than wood for heating your home, while failing to mention gas.
SPAAAAAAAAACE
Jane, before you try to lecture people about orbital mechanics, you should first make sure you understand more fundamental concepts like "conservation of energy".
I've already pointed out that Jane's hopelessly confused about the word "net", but that's just one of the mistakes Jane packed into these few sentences.
Jane's also wrong to imply that energy conservation across one choice of boundary could somehow contradict energy conservation across another boundary choice. That's impossible. Many boundary choices are inconvenient but they all have to be consistent. Otherwise, how could we possibly tell which boundary choice was correct?
So Jane can't object to the simple energy conservation equation I derived by claiming that some other boundary choice would somehow contradict my equation. That's completely impossible, and if Jane doesn't understand that point then he should learn about conservation of energy: example (backup), example (backup), example (backup).
As you can tell after reading those introductions, here's how to apply conservation of energy. Draw a boundary around the heat source:
power in = electrical heating power + radiative power in from the chamber walls
power out = radiative power out from the heat source
Since power in = power out through any boundary where nothing inside is changing:
electrical heating power + radiative power in from the chamber walls = radiative power out from the heat source
I put the boundary around the heat source so the boundary is in vacuum. That's because radiation can't travel through opaque solids like the heat source. So the only way to obtain an energy conservation equation with radiative terms is to place the boundary around the heat source.
For example, I calculated the enclosing shell's inner temperature by drawing the boundary within the enclosing shell. This boundary was inside aluminum, so heat transfer through it was by thermal conduction, not radiation. Notice that even this boundary choice leads to a conduction equation where electrical heating power depends on the cooler chamber wall temperature. That's because all boundary choices have to be consistent. The resulting equations can't contradict each other unless one of them is wrong.
After I asked Jane to explain exactly where his boundary would be drawn, Jane replied:
Which is completely fucking irrelevant to the question of soft landing a heavy object on Mars.
In other words, a unit that's completely unlike the one that will be required on Mars... It doesn't have to deal with abrasive dust... it doesn't have to compress and liquify the output gasses...
etc... etc...
A science fiction short story used it as a plot device decades ago. Might've been in an ACE or Tor printing, so that probably dates it to the late 1960s? The Bad Guys dropped into the planet's orbit, more or less matched speeds with the planet (remember, they need to move fast enough to avoid the well documented "Bug on the Windshield" Effect), and "simply" let the planet drive under them. They faced the same problem that NASA does, too. The story hinged on the difficulties of landing in the smallest number of pieces possible.