Difference between revisions of "Landing on Mars"
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<blockquote>the 2009 Mars Science Laboratory (MSL) rover, weighing 775 kilograms (versus MER at 175.4 kilograms each) requires an entirely new landing architecture. Too massive for airbags, the small-car sized rover will use a landing system dubbed the Sky Crane. "Even though some people laugh when they first see it, my personal view is that the Sky Crane is actually the most elegant system we've come up with yet, and the simplest," said Manning. MSL will use a combination of a rocket-guided entry with a heat shield, a parachute, then thrusters to slow the vehicle even more, followed by a crane-like system that lowers the rover on a cable for a soft landing directly on its wheels. Depending on the success of the Sky Crane with MSL, it's likely that this system can be scaled for larger payloads, but probably not the size needed to land humans on Mars. (See Ref #1) </blockquote> | <blockquote>the 2009 Mars Science Laboratory (MSL) rover, weighing 775 kilograms (versus MER at 175.4 kilograms each) requires an entirely new landing architecture. Too massive for airbags, the small-car sized rover will use a landing system dubbed the Sky Crane. "Even though some people laugh when they first see it, my personal view is that the Sky Crane is actually the most elegant system we've come up with yet, and the simplest," said Manning. MSL will use a combination of a rocket-guided entry with a heat shield, a parachute, then thrusters to slow the vehicle even more, followed by a crane-like system that lowers the rover on a cable for a soft landing directly on its wheels. Depending on the success of the Sky Crane with MSL, it's likely that this system can be scaled for larger payloads, but probably not the size needed to land humans on Mars. (See Ref #1) </blockquote> | ||
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== References == | == References == | ||
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Revision as of 18:50, 16 January 2012
Landing on Mars is a difficult problem.
To date over 60% of the missions [to the Martian surface] have failed. The scientists and engineers of these undertakings use phrases like "Six Minutes of Terror," and "The Great Galactic Ghoul" to illustrate their experiences, evidence of the anxiety that's evoked by sending a robotic spacecraft to Mars — even among those who have devoted their careers to the task. But mention sending a human mission to land on the Red Planet, with payloads several factors larger than an unmanned spacecraft and the trepidation among that same group grows even larger.[1]
If we need a four hundred foot diameter parachute manufactured in space out of aluminum oxide fiber and sent to Mars in stiff deployed condition instead of being packed, we will not learn about it unless we see a need to experiment. Such a parachute might merit investigation. It would avoid opening shock and might be sufficiently heat resistant to maintain structural integrity during the entire descent in Mars' low gravity well. The larger the diameter of the parachute, the less the max g loading. So let us be honest with ourselves about all necessary colonization technology.
The expected max temperature for ballistic entry into Mars atmosphere is expected to be a thousand or more Kelvin degrees above the melting point of aluminum oxide so coating course aluminum oxide fibers with potassium oxide which decomposes at 490 Centigrade might protect the fibers through atmospheric entry by ablative cooling or it might not. A mixture of potassium and sodium oxides as a coating or Teflon as a coating are things that are conceivable. Engineers in this specialty would have a better idea.
High Lift Vertical Landing Vehicle
Another alternative with a greater probability of working, but possibly high cost, is a delta winged entry vehicle or lifting body with insulation like that on the space shuttle. The insulation would be somewhat cheaper because Mars atmospheric entry is less demanding than Earth reentry. After losing most of its orbital velocity to the atmosphere by heating the atmosphere in passing, this vehicle would fly supersonic close to the ground then ignite its rockets for landing. Then it would perform a Pugachev's Cobra[2] maneuver losing horizontal velocity by drag and by rocket thrust. It would then touch down on its tail. Rocket thrust directly into the supersonic slipstream of Mars' atmosphere will not work to safely land on Mars because the supersonic slipstream that the lander flies into would carry the noise of the rocket exhaust right back to the lander. The potential for the chaotic forces of this rocket noise to destabilize the lander's orientation and damage its structure rule out this technique. In the Pugachev's Cobra maneuver, rocket thrust is never directed directly into the supersonic slipstream. The rocket thrust always has a vertical component while the slipstream moves horizontally until the slip stream velocity is reduced to a negligible value.
This sort of vehicle might approach the point of entering a Pugachev's Cobra maneuver by flying horizontally near Mars' surface while increasing angle of attack to maintain lift while killing velocity. At a pitch attitude of 45 degrees there is little lift left to be gained by increasing angle of attack. This should occur at about Mach 2.5, which is about 600 meters per second on Mars. Then the rockets are ignited generating two Mars gravities of acceleration and the angle of attack is further increased past 90 degrees to generate negative lift and keep the vehicle in horizontal flight. As the speed decreases and negative lift generated by the wings decreases, the pitch angle is increased to reduce the component of rocket thrust in the vertical direction and increase the component of rocket thrust directed to braking. As the vehicle eventually slows to a stop in horizontal motion, a combination of throttling and thrust deflection reduces thrust to about 1 Mars gravity, the vehicle moves to a 90 degree pitch angle and settles on its tail. A guesstimate of the required rocket delta V for killing the last 600 meters per second and landing in this way is about 850 meters per second. This includes the amount of speed lost to atmospheric drag and very substantial gravity losses.
Another Alternative is the Sky Crane
the 2009 Mars Science Laboratory (MSL) rover, weighing 775 kilograms (versus MER at 175.4 kilograms each) requires an entirely new landing architecture. Too massive for airbags, the small-car sized rover will use a landing system dubbed the Sky Crane. "Even though some people laugh when they first see it, my personal view is that the Sky Crane is actually the most elegant system we've come up with yet, and the simplest," said Manning. MSL will use a combination of a rocket-guided entry with a heat shield, a parachute, then thrusters to slow the vehicle even more, followed by a crane-like system that lowers the rover on a cable for a soft landing directly on its wheels. Depending on the success of the Sky Crane with MSL, it's likely that this system can be scaled for larger payloads, but probably not the size needed to land humans on Mars. (See Ref #1)
People norlmaly pay me for this and you are giving it away!
