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Base Synchronization

Lesson Objectives

In this tutorial you will learn the basic steps for Base Synchronization that illustrates the procedure for adjusting the orbit of space craft to align with a landing sight for reentry. The following subjects will be presented.

  1. Concept

  2. BaseSync MFD

  3. Instrument Setup

Suggested Reading Topics:

  1. 4.1.7 Returning from Space (PDF)

  2. ORBITER Space Flight Simulator Manual - 2006 Edition Sections: 16, 19.3

  3. Delta-glider Operations Manual

  4. Base Synchronization Manual

Module Installations:

  1. Base Sync

Sections 1: Concept

When a spacecraft is returning to land at a spaceport or other landing location, it must align and sync it's orbit with the landing location. During orbital rendezvous  each vessel has its own orbit elements, and one simple matches his current orbital element to that of the target vessel by changing his inclination apogee and so forth. This is not necessarily the case when landing at a space port, because of verity of factors such as atmosphere. and rotation of the planet and must be taken into account. The landing base does not have a traditional orbit, because it is attached to a ridge body that is has its own rotation speed and may be located on a planet that has an atmosphere, Figure1.  The orbital elements of the base can be displayed on some MFDs. The techniques we use to compensate for the rotation of the planet and atmosphere are different from orbital rendezvous and require the use of BaseSync and AeroBrake MFDs

Figure 1 Base or landing sights
rotating on a planet

Section 2: BaseSync MFD

The Base Synchronization can be used to align the orbit  plane, and deorbit a space craft, with a landing location on the surface of a planet. Synchronization can be accomplished by selecting the target ground base or entering the latitude and longitude of the landing site. The green line marks the space current position and the yellow line and text indicates the closet intercept to the landing site, Figures 2.1 and 2.2.

Figure 2.1 Read outs Base Sync MFD

Figure 2.2 Base Sync MFD

Section 2.1: Encounter Modes

The encounter mode gives the pilot astronaut four options on how to sync the orbit of the space craft to a particular landing site. The four modes are:

  • Latitude Mode: Shows the closest intercept points where the space craft orbit crosses the landing sites latitude. This mode can be used for fast rotating planets such as Mars or Earth, when the inclination between the and target's latitude is small, Figure 2.3.

Figure 2.3 Latitude Mode1
  • Closest Passage Mode: Gives information for the point of closes passage to the landing sight. There will be only on point in an orbit that will have the minimum distance to the target base or landing point, Figure 2.4.

Figure2.4 Closest Passage Mode2
  • Apoapsis / Periapsis  Mode: These modes use the ships apoapsis or periapsis to adjust the orbital plane for base synchronization.

Section 2.2: Equator and Direct Modes

The BaseSync MFD also has two inclination adjustment modes that are used to adjust the inclination of the orbit.

  • Equator mode is best used when the when the difference between the inclination and the target latitude is small and the rotation of the planet is fast like Earth or Mars. The inclination of the orbit will need to be adjusted so that the target base will be with in the reentry zone, Figure 2.5.

Figure 2.5 Equator Mode3
  • Direct mode is can be used for all types of planetary body regardless of rotation speed, Figure 2.6. It is also used to make fine course adjustment prior to reentry.

Figure 2.6 Direct Mode4

Section 2.3: De-Orbit Program

The De-orbit mode is used on the orbital plane is adjust to be in sync with target base or landing site. The program requires three parameter to calculate reentry path: reentry angle (ReA), reference altitude (RAI), and reentry anticipation angle (Ant). Each parameter can be selected using the buttons on the MFD, Figure 2.7.

Figure 2.7 DEO MFD
  • TrL is the true longitude of the burn position
  • BT is the remaining burn time

  • ANG will setup the reentry angle (ReA)

  • ANT will setup the reentry anticipation angle (Ant)

  • ALT sets the reference altitude for the re-entry maneuver (RAl)

The reentry angle is the angle between the local horizontal and the velocity vector of a reentering space craft, Figure 2.8

Figure 2.8 Reentry Angle5

The reference altitude is the altitude that the space craft will mostly likely encounter the atmosphere of the planet. For planets that have no atmosphere the reference altitude is zero.

The reentry anticipation angle is the angle from the point where the space craft reaches the reference altitude and the target base, or landing site, Figure 2.9.

Figure 2.9 Reentry Path6

Section 3: Instrument Setup

The BaseSync MFD is the primary navigation aid used during reentry to align and synchronize your orbit with a target landing site or base. Use the following procedures to set up the BaseSync.

BaseSync MFD

  1. Selecting TGT and enter the base, or longitude and latitude of landing site, Figure3b and 3c.

  2. Select the E/D Equator or Direct Mode. Use the Equator Mode for fast rotating planets. The Direct mode can be used for all reentry situations.

  3. Cycle through the encounter mode to determine which reentry path is optimal for your current orbit. This will typically be the one that can be accomplished with the fewest orbit or has the smallest relative inclination.

Use the following checklist to ensure that the flight instruments are set up correctly.

bullet

Deorbit and Reentry: Instrument Setup CL

Citation:

Pictures:

1,2,3,4,6 Base Synchronization Manual, Jarmo Nikkanen

5 Returning from Space, FAA

 

 

 

 

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Last modified: 01/26/11