Mars Pathfinder and Sojourner
The Mars Pathfinder mission began as MESUR Mars Environmental Survey , a 1991 proposal for a network of as many as 16 Mars landers to perform network science meteorology and seismology on distributed sites using nominally inexpensive landers. One prominent approach to reducing the unit cost of the landers was to use a semi-hard landing approach with airbags rather than a retrorocket system. The landing system proposed was sufficiently radical that a technology demonstration flight validation...
Hover
Although obviously not an efficient part of a trajectory, the ability to hover may be useful. It can be shown that a vehicle hovering with rocket propulsion that has a mass ratio of 1 e 1 2.718, -0.367 can do so for a period in seconds equal to the specific impulse, which is also usually expressed in seconds. This neat result is a vivid demonstration of the otherwise unobvious dimensions of specific impulse. Stable hover requires throttlable propulsion. This can be achieved either Combined...
Instrumentation
To land from orbit requires the controlled change and therefore the measurement of the spacecraft's dynamical state. During atmospheric entry, deceleration measurements or during descent, pressure measurements can provide Figure 5.3. Slant range versus time during NEAR descent to Eros. The altitude at the start was about 5 km from Dunham et al., 2002 . Figure 5.3. Slant range versus time during NEAR descent to Eros. The altitude at the start was about 5 km from Dunham et al., 2002 . convenient...
Mars Science Laboratory
Currently planned for 2009, the Mars Science Laboratory is a large, long-range rover equipped with a sophisticated and diverse payload. MSL is also due to use a new 'sky crane' landing technique, landing on its own wheels rather than encased in a lander platform. Objectives Biological objectives Determine the nature and inventory of organic carbon compounds Inventory the chemical building blocks of life carbon, hydrogen, nitrogen, oxygen, phosphorous, and sulfur Identify features that may...
Mars Pathfinder
Mars Pathfinder was highly successful, combining technological and scientific goals, and lander and rover elements, to become the first Martian surface mission since the Viking Landers. For more details see the Case Study, Chapter 24 Figures 17.6 and 17.7 . Technological demonstrating the feasibility of low-cost landings on and exploration of the Martian surface Scientific atmospheric entry science, geological characterization of the landing site, meteorology, and long-range and close-up...
Part I
Engineering issues specific to entry probes, landers or penetrators This part of the book is intended to act as a guide to the basic technological principles that are specific to landers, penetrators and atmospheric-entry probes, and to act as a pointer towards more detailed technical works. The chapters of this part aim to give the reader an overview of the problems and solutions associated with each sub-system flight phase, without going into the minutiae. Mission goals and system engineering...
A
Figure 4.1. Staging of the Pioneer Venus large-probe entry shell and parachute. Entry interface was defined at 200 km altitude, with the main deceleration lasting about 38 s. At about 70 km altitude, a mortar deployed a pilot chute, which removed the aft cover and deployed the main chute. The entry shield is then allowed to fall away, and after 16.5 minutes at 48 km the main parachute was jettisoned, allowing the probe to fall faster. Free descent took another 39 minutes. This descent sequence...
Examples Luna and Apollo
The soft-lander Luna 16, which returned samples of lunar soil to Earth, was placed first into a 110 km circular lunar orbit. It was then put into a 15 X 106 km orbit, with landing approach to be made from perilune. The vehicle simply killed its 1.7 km s 1 orbital speed and then fell vertically. The free-fall was monitored by a radar altimeter, and arrested at an altitude of 600 m 200 m s 1 by another burn. Again, note the low altitude of these manoeuvres to maximize propulsive efficiency. The...
Pioneer Venus probes
Pioneer Venus involved two launches an orbiter and a 'multiprobe bus' spacecraft to carry four entry probes, for release into the Venusian atmosphere prior to the destructive entry of the bus itself. To meet the objectives of both detailed measurements in the atmosphere and multiple measurements at different locations, one large probe and three smaller ones were flown, the Large Probe having seven times the payload capacity of each of the Small Probes Day, North and Night . The bus also carried...
Mars M and M landers
These were the first attempts to soft land on Mars, following the failed 2MV-3 entry probe attempt in 1962 and the landers deleted for mass reasons from the Mars 69 mission. A lander with a Luna 9-style four-petalled opening righting mechanism was encased in crushable material and delivered by parachute and braking rockets from the entry assembly Figure 17.4 . Prime contractor Launch site, vehicle Landing site co-ordinates End s of mission s Soft landing on Mars and investigations of the...
Parachute types
The design of parachutes and related systems is a somewhat arcane science e.g. Knacke, 1992 Murrow and McFall, 1968 of sufficient complexity that empirical testing remains the only trustworthy design tool. Different parachute geometries are available with different inflation performance, drag coefficient, stability, manufacturing cost and so on. The lowest cost type of parachute is the cruciform - this is easily manufactured as two strips of fabric sewn at an orthogonal intersection. These are...
Mars retrorockets in atmosphere
Some additional remarks are appropriate about descent in the Martian atmosphere. Terminal velocity in the thin Martian atmosphere is typically too large to permit soft landing only using a parachute. Even the semi-hard landing of the Mars Pathfinder vehicle used a retro-rocket to null the descent velocity just prior to impact. A scientific concern is that the plume from the descent engines should not deposit fuel contaminants at the landing site, or significantly erode the surface material...