MANNED SPACEFLIGHT: GEMINI RENDEZVOUS MISSIONS

in the United States effort to attain preeminence in space the Germany program is a major step the first phase of this program began with an unmanned flight on April 8 1964 the primary objectives of the Germany program are first to provide long-duration manned spaceflight experience and second to develop operational rendezvous and docking techniques Germany is a two-man spacecraft manufactured by the McDonnell Aircraft Corporation st. Louis Missouri the spacecraft will be launched into orbit by a modified Titan two launch vehicle developed by the Air Force and the Martin company Baltimore Maryland the Germany target vehicle will consist of a modified Aegina D vehicle manufactured by the Lockheed missiles and space company Sunnyvale California it will be launched by an Atlas launch vehicle which was developed by the air force and the General Dynamics Corporation San Diego California it is the purpose of this film to explain the rendezvous and docking concepts to be studied and evaluated in the Gemini program these studies will lead to rendezvous and docking techniques for use first in Apollo and later for other NASA and DOD manned spaceflight programs the rendezvous and docking phase of Apollo is discussed first in Apollo lunar rendezvous and docking will be accomplished after lunar surface operations at this point one member of the three-man flight crew is orbiting the moon in the command module the other two crew men on the lunar surface are preparing for the launch of the lunar excursion module or LEM and the subsequent rendezvous and docking maneuver after docking they will rejoin the first crew man in the command module during countdown the orbiting command and service module is located by using the LEM onboard radar range and bearing angle information are fed to the onboard computer which programs the trajectory required to place the LEM into a direct descent transfer orbit for rendezvous and docking at a predetermined time the LEM ascent engine is fired should the flight path deviate from the reference trajectory the computer calculates the Corrections necessary to intercept the command and service module at the original rendezvous point at the proper time the LEM is then maneuvered into the docking position after docking the astronauts transfer to the command and service module for return to Earth the study and detailed evaluation of six different rendezvous concepts is planned for the Gemini program the first of these is the radar computer method that is both the onboard radar and computer are used in this mission as in subsequent missions the Atlas Agena target vehicle is first launched into orbit from Cape Kennedy Florida approximately nine minutes after liftoff the Agena is inserted into a circular orbit around the Earth meanwhile the countdown for the Gemini spacecraft has preceded the first opportunity to launch the spacecraft occurs after the completion of one orbit of the Agena after completion of the sustainer engine or second stage firing the spacecraft is separated from the launch vehicle by firing the aft thrusters of the spacecraft orbital attitude and maneuvering system the spacecraft is placed in an elliptical orbit approximately 1,200 nautical miles behind the Agena target vehicle this orbit is smaller than that of the Agena target vehicle and is near coplanar since the spacecraft orbit is smaller than that of the Agena the spacecraft immediately begins to close the distance between the two vehicles approximately 45 minutes after insertion the spacecraft reaches the first Apogee or high point of the elliptical orbit after passing the first Apogee the astronauts are advised by the ground tracking network of the orbital changes required for rendezvous included will be a change of orbital plane and an extension of the spacecraft orbit the astronauts begin preparations for the orbital Corrections immediately after passing the second orbital perigee or a low point and entering the second orbit the spacecraft is oriented so that the small end of the spacecraft is forward and in line with the orbital path this is necessary for alignment of the guidance platform after aligning the guidance platform the astronauts prepare for the orbital plane change maneuver first the attitude thrusters of the spacecraft orbital attitude maneuvering system are fired to rotate the spacecraft at right angles to the flight path at the point of intersection of the two orbital planes the command astronaut fires the forward thrusters this maneuver rotates the orbital plane of the spacecraft to be coplanar with that of the Agena target vehicle after completion of the plane change maneuver the guidance platform is again aligned at the second spacecraft Apogee the command astronaut fires the aft firing thrusters to increase the speed of the spacecraft this raises the spacecraft perigee thus enlarging the orbit and slowing the catch-up rate sufficiently for rendezvous at the planned time after entering the third orbit the astronauts are advised by the ground tracking network as to the velocity increase required to place the spacecraft into a circular orbit at the third Apogee as the spacecraft advances toward the third Apogee the astronauts align the spacecraft for thruster firing at the apogee the command astronaut fires the aft thrusters and the spacecraft is placed into a circular orbit this orbit remains smaller than the Agena orbit allowing the catch-up to continue but at a slower rate the spacecraft search radar is then placed into operation and after a short warmup period begins the search for the Agena target vehicle when the Agena is located the radar lock-on light comes on advising the astronaut that the target has been acquired the astronaut then Orient's the spacecraft to point directly at the Agena target vehicle the computer is then switched into the rendezvous mode initiating the onboard computer program the velocity increases required for rendezvous are computed from data furnished by the radar and guidance platform the increase is required are displayed on the incremental velocity indicator every 100 seconds as the spacecraft catches up with the Agena target vehicle the additional velocity required for rendezvous decreases when the velocity increase reaches a minimum and can be achieved with available spacecraft fuel the astronaut the presses the start compute button initiating at a predetermined time initial terminal rendezvous functions the start compute light comes on and the command astronaut fires the aft thrusters this maneuver puts the spacecraft on a transfer orbit to intersect the Agena orbit at the proper time for rendezvous after completion of the initial terminal rendezvous maneuver the astronauts reacquire the Agena with the radar after gathering radar data for approximately three minutes the astronauts rotate the spacecraft to small end forward and align the platform after eight minutes of platform alignment the astronauts reacquire the Agena with the radar to provide updated radar data to the computer approximately one minute later the computer indicates whether an intermediate correction maneuver is required if so the astronauts immediately begin to apply the correction if necessary a second intermediate correction maneuver can be performed a final terminal rendezvous maneuver is then performed to match the orbit of the spacecraft to that of the Agena target vehicle this maneuver places the spacecraft in orbit slightly ahead of the target vehicle the aft thrusters are then fired to bring the spacecraft into contact with the Agena for the final docking operation the front docking approach may be modified by turning the Agena in orbit for an approach from the rear the second rendezvous technique to be investigated will be the rendezvous radar and optical sight method in this method it is assumed that the onboard computer has malfunctioned and the astronauts must rely on the onboard radar and optical sight for rendezvous based on velocity information pre-planned and updated as required by the ground network the astronauts fire the aft thrusters for the initial terminal rendezvous maneuver this maneuver puts the spacecraft on the transfer orbit with a spacecraft pointing directly at the Agena the astronauts observe its relative motion against a star background through a calibrated optical sight the Agena appears as a blinking light if the Agena appears to drift against the star background the astronauts fire the spacecraft lateral thrusters to stop the apparent drift this results in a constant bearing angle approach to the Agena target vehicle after checking the radar range and range rate display the astronauts then fire the forward thrusters to correct the relative closure speed between the Agena vehicle and the spacecraft when the spacecraft has approached to within docking range of the Agena the astronauts begin the docking phase of the mission for the third method of rendezvous the astronauts employ the optical sighting technique it being assumed that both the onboard radar and computer have malfunctioned again based on velocity information pre-planned and updated as required by the ground network the astronauts fire the aft thrusters to place the spacecraft on a transfer orbit using the optical sight the astronauts make two timed angular measurements of the apparent drift of the Agena after completing the angular measurements the astronauts then fire the spacecraft lateral thrusters to stop the Agena drift against the star background using the timed angular measurements and the known thrust level the astronauts calculate the range and range rate to the Agena target if for example the relative range rate is too low the astronauts fire the aft thrusters to increase the rate of closure between the spacecraft and Aegina these steps are repeated until the spacecraft is within docking range of the Agena the docking operation is then completed in the fourth rendezvous investigation rendezvous is planned by the direct descent method as in Apollo in this method the intermediate parking orbits will be omitted after the Agena has been placed into orbit the Gemini vehicle is launched in the direct descent rendezvous the launch time and trajectory must be more precise than in the earlier methods in which parking orbits were used to rendezvous and dock after spacecraft separation the astronauts correct the orbit insertion conditions by firing the spacecraft aft thrusters in accordance with computer commands after checking spacecraft systems and activating the radar the astronauts search for and acquire the Agena Midway to the first Apogee and rendezvous with the Agena the astronauts fire the spacecraft aft thrusters again in accordance with computer commands thus completing a mid-course correction maneuver the astronauts again acquire the Agena with a spacecraft radar the inertial guidance platform is realigned and additional radar information is acquired after Corrections are made the final terminal rendezvous maneuver is performed so that the orbits of the spacecraft and Agena target vehicle coincide near the first apogee when the spacecraft comes within docking range of the Agena the aft thrusters are fired to complete the docking phase of the mission in the fifth method rendezvous will again be made by direct descent however the reference trajectory and aim point concept will be used as in the Apollo lunar rendezvous in this method the Gemini spacecraft simulates the lunar excursion module and the Agena target vehicle simulates the Apollo command and service module in orbit around the moon approximately 15 minutes after launch of the Gemini spacecraft the astronauts acquire the Agena target vehicle with a Gemini radar based on the radar information the Germany computer calculates the deviation of the gemenese spacecraft from the reference trajectory and the necessary velocity Corrections are made to rendezvous with the target at the originally specified time and aim point after making the Corrections the astronauts reacquire the Agena with the radar further velocity Corrections are then calculated by the Germany computer and applied by the astronauts the final terminal rendezvous maneuver is performed to match the orbits of the spacecraft and target vehicle the aft thrusters are then fired to complete the docking operation in the sixth method of rendezvous the astronauts will perform the rendezvous and docking maneuvers which would be required should an abort be incurred during the lunar descent phase of an Apollo mission again the Gemini spacecraft will simulate the LEM and the Agena will simulate the command and service module beginning at the apogee the Gemini spacecraft starts on its descent trajectory toward the Earth's surface which in this case represents the lunar surface a descent engine malfunction is assumed and the Gemini thrusters are fired to place the spacecraft in an abort trajectory the astronauts then acquire the Agena target with the onboard radar to provide data to the on-board computer for rendezvous with the target approximately 3/4 of an orbit after the abort from the descent trajectory the gemenese spacecraft approaches the rendezvous point with the Agena the astronauts fire the spacecraft thrusters to match the Agena and Gemini velocities and the docking operation is executed in these six rendezvous studies in the Gemini program a method using both the onboard radar and computer for rendezvous will be studied another method using the onboard radar and optical sight for rendezvous will be evaluated a method using the optical sight only will be investigated the direct descent rendezvous method will be evaluated the direct descent rendezvous utilizing the reference trajectory and aim point concept will be studied and finally a technique for re rendezvous in case of an abort condition during the lunar descent phase of an Apollo mission will be investigated the rendezvous techniques and experience to be gained in these six studies will be utilized in future NASA and DOD programs as well as in Apollo as the United States continues manned exploration of space