In mid-2002, while revieiwing the material on Mark Gray's Apollo 11 DVD (www.spacecaftfilms.com), I saw a film showing Buzz Aldrin and Neil Armstrong at the LLRF on or about 28 June 1969. Knowing that Dave Scott had not thought of the LLRF as being a very faithful LM simulator, asked Neil if he had any thoughts about why he might have used it just over two weeks before launch. He did not remember such as session but said "I found in my log book that I flew from Patrick AFB (Cape) to Langley AFB in a T-38 on June 30, 1969 and returned on July 1. My log suggests that I was alone." He added, in a subsequent note, "I viewed the LLRF as more of an engineering development tool than a trainer."
The various film clips of activities do not show Neil and Buzz together; and, indeed the cockpit in the LLRF simulator had room for only one person. The Apollo 11 Crew Training Summary indicates that Buzz used the LLRF on Friday 28 June, probably only in the afternoon after a morning session in a LM simulator (probably at the Cape), and again the following day. Neil used the LLRF on Monday, in agreement with his personal log book.
The following is an extract of Neil's lecture 'Wingless on Luna' given in 1988 at the Wings Club in New York City. It is used with permission from the author.
Independently, at the NASA Langley Research Center, an alternate approach to lunar simulation was initiated. Again the idea was to duplicate the lunar gravity and control characteristics. The method was to lower the vehicle apparent weight to its lunar equivalent by a lifting upward with vertical cables attached to a traveling bridge crane.
A complex electro-hydraulic system kept the crane platform directly over the machine and the cables vertical - even during translational and angular motions and weight changes due to fuel usage. It had a wonderful assortment of structural, cable stretch and pendulous frequencies requiring innovative compensation systems. It was, indeed, an engineer's delight.
The vehicle was attached to the cables through gimbal rings allowing pitch, roll and yaw motions produced by a hydrogen peroxide rocket attitude control system. The one sixth weight not lifted by the cable system was lifted by throttleable hydrogen peroxide rockets fixed to the vehicle structure.
After the kinks were ironed out, it worked surprisingly well. They flying volume - 180 feet high, 360 feet long, and 42 feet wide - was limiting, but adequate to give pilots a substantive introduction to lunar flight characteristics.>p> Pilots soon adapted to the challenges of combining an acceleration command lift control and an angular rate command attitude control. They found it was difficult to maintain a precise descent angle and difficult to eliminate all drift before touchdown. Generally, horizontal drift could be reduced to below 3 fps. Vertical velocity at touchdown could be slightly higher. Smooth control inputs were a necessity to minimize fuel consumption by the attitude rockets.
Control characteristics could be varied over a wide range. Control powers (for pitch and roll) below 5 degrees per second squared were generally determined to be excessively sluggish, while control powers above 15 degrees per second squared were judged to be 'jerky'. Maximum control rates of 10-15 deg/sec were judged satisfactory. Acceleration command (direct on-off) systems were generally found to be acceptable, but required high pilot workload and constant attention. Clearly, this was a less than desirable alternative when the pilot would be expected to be monitoring other systems and looking for an acceptable landing site.
The cable system could be locked at any time in the event of a loss of control, thereby preventing accidents. This feature allowed the pilots to investigate unorthodox attitude, trajectory and control combinations which would be impractical in a free-flying simulator.
|Journal Home Page||Apollo 11 Journal Index|