Exploring space information, concentrating on the Moon.
Wednesday, December 14, 2011
Landing - it is in the details -
When you talk about landing humans on another planet or moon there are a lot of decisions that have to be made. On the FPSPACE list a question was asked why the American Lunar Modules had insulation wraps on the legs and the Soviet Lunniy Korabl spaceship did not.
The LK (Lunny Korabl—"lunar ship") was a Soviet lunar lander and counterpart of the American Lunar Module (LM). The LK was to have landed up to two cosmonauts on the Moon. It completed development and was test flown successfully in Earth orbit, but never reached the Moon because development of theN1 rocket, required to take it to the Moon, was unsuccessful.
This PDF document has a lot of information about the Lunar Module landing-gear. The 60 page NASA Technical Note explains why paint was not enough to keep the temperature within limits especially if the astronauts had to land with the rocket engine still firing as they touched down. Testing, testing, testing, and attention to detail. And how do you drop test at 1/6 G on a 1 G Earth? :-)
Landing-gear thermal-insulation design is based on several requirements. Landing-gear temperatures must be maintained at or below design levels to ensure positive structural margins of safety and proper mechanical operation during deployment and landing. Temperature control of the honeycomb energy absorbers within specified limits is necessary to ensure that the crush loads will be within proper levels.
Based on these requirements, an estimated 8.0 pounds of thermal paint was allotted to landing-gear thermal control early in the development program. The weight history of the landing-gear thermal insulation is shown in table II. As thermal testing and analysis progressed, it became apparent that 8.0 pounds of thermal paint were totally inadequate for landing -gear thermal protection. Additional insulation had to be provided because of the effects of LM reaction control system (RCS) plume impingement, The impingement from the RCS plume adversely affected the structural temperatures and the temperature of the honeycomb energy absorbers in the primary and secondary struts. Landing-performance analysis, for which the energy -absorber load levels that are temperature dependent were used, showed considerable degradation in landing-gear performance for worst -case combinations of honeycomb temperatures and landing conditions. The outcome of this investigation was the addition of thermal-insulation blankets to the main structural members of the landing gear. The thermal-insulation weight (table II) was increased to 29.4 pounds for the Ap0110 9 LM (LM-3) and Apollo 10 LM (LM-4), which were the first two LM flight articles to have landing gears.
A lot of decisions to be made for something as big as the Apollo missions. A lot of people and companies with their own ideas as to what would be the best way to get us to the Moon and back. You can read about it on-line if you haven't already. When talk about new missions that might take humans to space I wonder how much is paid to the details.
I took a look in this book. Just fold everything up in a neat package until you get ready to leave lunar orbit. Then stretch out your legs and prepare to land on soil that has only been tested by unmanned landers. Will you slide sideways, will you sink into the regolith, will you tip over on the side of meteor crater? Details, details, details!
- LRK -
a pictorial essay of the engineering and construction of the Apollo command and service modules : the historic spacecraft that took man to the moon.
In the book, "Virtual LM" by Scott P. Sullivan, he has pictured on p.115, Landing Gear Thermal Insulation. From the list of items: ... (Q) Primary Strut Thermal Covering (1/2 mil Aluminized Kapton), (Q2) Primary Strut Thermal Covering (5 mils Aluminized Kapton), (R) Landing Pad Thermal Covering (1/2 mil Aluminized Kapton), (S) Probe Thermal Coating (2 mils Aluminzed Kapton).
On pages 75 - 92 he has pictured the Landing Gear Assembly in its various configurations. Looks like a lot of electrical and mechanical considerations.
On page 77 Scott has a write up about the landing gear and in the last paragraph he states, "The landing gear primary strut had a footpad at the bottom that was 37 inches in diameter and was attached to the strut with a ball-socket fitting, allowing radial movement. The landing pad was an aluminum honeycomb construction and its large diameter ensured minimal penetration of the LM on lunar impact. During launch, four straps held the pads in a fixed position on the strut. The straps would shear or bend on impact with the lunar surface, permitting the pad to conform to the irregularities of the lunar surface."
On page 83 Scott has a paragraph about the lunar surface-sensing probes that were on on three of the four landing struts. They were retained in a stowed position up against the primary strut until landing gear deployment. During the deployment, mechanical interlocks were released permitting spring energy to extend the probes so that they were approximately 5 feet below the bottom of the footpad. Pressure on the probe head completed an electrical circuit letting the astronauts know to shut off the engine.
And how much weight will you have to add to protect you from radiation from space? Will you want to land on legs? How many legs? If you land on an asteroid, do I need legs? If I land on Mars, do I need legs? Those details.