A&AE 450 – Senior Design

Jeremy Davis

Group A – Aerodynamics

Preliminary Design Analysis

January 23, 2001

ERV to Mars

• There are three options for re-entry into Mars atmosphere

1. Aerobraking maneuver

2. Aerocapture maneuver

3. Direct re-entry

Aerobraking Maneuver• Advantages

1. Uses much less propellant than a purely propulsive maneuver.1

2. Deceleration is taken over many upper-atmospheric passes which results in lower g-loads on ERV.

3. With each atmospheric pass, orbiter can analyze drag data and plan small burns accordingly which leaves virtually no risk of mission failure during maneuver.2

4. History: Has been completed successfully during Magellan mission and Mars Global Surveyor (MGS).3

Aerobraking Maneuver (cont’d)

• Disadvantages

1. Depending on needed deceleration the maneuver lasts several days to several months.4

2. Rarified flow calculations can be difficult at this level.

Aerocapture Maneuver

• Advantages

1. Similar to aerobraking, aerocapture uses much less propellant than a purely propulsive maneuver.

2. Because the ERV enters farther into the atmosphere than aerobraking, a plane change could be made if needed.5

3. Maneuver takes much less time than aerobraking.

Aerocapture Maneuver (cont’d)

• Disadvantages

1. Very intense heating during initial maneuver virtually requires ablative surfaces which are very difficult to model.6

2. Because of lower altitude, density fluctuations can present a major risk to mission success.

3. G-load during initial maneuver can be high (relative to aerobraking only).

Direct Re-Entry• Advantages

1. Very quick and simple compared to aerobraking and aerocapture maneuvers.

2. History: Has been used for past re-entry capsules (i.e., Apollo)

• Disadvantages

1. Very sensitive to atmospheric changes and trajectory errors.

2. Because of high entry speeds, G-loads could be excessive.

ERV to Earth

• There are three options for re-entry into Earth atmosphere

1.Aerobraking maneuver

2.Aerocapture maneuver

3.Direct re-entry

Maneuver Differences for Earth

• In the case of an aerobraking maneuver, spending weeks in orbit around Earth could be unappealing to astronauts and would put unnecessary constraints on food requirements.

• Aerocapture maneuver could enable a Space Shuttle rendezvous for re-entry.

• Aerocapture could be too risky for manned space flight (further analysis intended).

References & Notes1. NASA, JPL. mars.jpl.nasa.gov/mgs/confrm/aerobexp.html gives a

comparison between Mars Global Surveyor, which used aerobraking, and Mars Observer (both of similar payload masses) showing Mars Observer’s launch mass 2.4 times that of MGS.

2. Walberg, Gerald. A Survey of Aeroassisted Orbit Transfer, AIAA 9th Atmospheric Flight Mechanics Conference, San Diego, Calif., 1982, mentions multi-pass aerobraking maneuvers are possible to be made “fail-safe” and that “…tracking data obtained during the early high-altitude orbits can be used to provide estimates of atmospheric density…”

3. From Ref. #1, gives a detailed analysis of the aerobraking procedure of the MGS.

4. From Ref. #1, the MGS aerobraking procedure was designed to last 4 months, due to a small error, it lasted 17 months. Magellan mission to Venus had a 44 day aerobraking procedure (from Ref. #2).

References & Notes (cont’d)

5. From Ref. #2, “Synergetic Plane Change” section.

6. From Ref. #2, “… aerocapture maneuvers produce relatively high values for both the heat-transfer rate and the heating time…”

Relevant Experience

• Courses Taken A&AE 439 A&AE 490 ( Research of Satellite Fuel Tanks in Zero-G

Environment, with Prof. Collicott) Currently taking A&AE 519 (Hypersonics)

• Computer Skills MATLAB, FORTRAN & Surface Evolver