We must meet a set of requirements to achieve mission objectives that mark the beginning of a space-mission planning. The re-entry phase of a mission is no different. The three most competitive requirements that must be delicately balanced are
• Deceleration
• Heating
• Accuracy of landing or impact
The vehicle’s structure and payload limit the maximum deceleration or “g’s” it can withstand. (One “g” is the gravitational acceleration at Earth’s surface—9.798 m/s2. The amount of deceleration is so high that even steel and aluminum can crumple like paper. Fortunately, the structural g limits for a well-designed vehicle can be quite high, perhaps hundreds of g’s. But in case of a fragile human payload, it would be crushed to death long before reaching that level. Humans can withstand a maximum deceleration of about 12 g’s (about 12 times their weight) for only a few minutes at a time.
Just as a chain is only as strong as its weakest link, the maximum deceleration a vehicle experiences during re-entry must be low enough to prevent damage or injury to the weakest part of the vehicle. But maximum g’s aren’t the only concern of re-entry designers. Too little deceleration can also cause serious problems. Similar to a rock skipping off a pond, a vehicle that doesn’t slow down enough may literally bounce off the atmosphere and back into the cold reaches of space.
Another limitation during re-entry is heating. The fiery trail of a meteor streaking across the night sky is an extremely good example to show that re-entry can get hot! This intense heat is a result of friction between the speeding meteor and the air. How hot can something get during re-entry? The Space Shuttle in orbit has a mass of 100,000 kg (220,000 lb.), an orbital veloc...
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... burn. This burn changes the Shuttle’s trajectory to re-enter the atmosphere by establishing a –1° to – 2° re-entry flight-path angle. After this maneuver, the Shuttle is on “final approach.” Because it has no engines to provide thrust in the atmosphere, it gets only one chance to make a landing!
Preparing to hit the atmosphere (just like a skipping stone), the Shuttle rotates its nose to a 40° angle of attack, that means the nose is pitched up 40° with respect to the velocity vector. This high angle of attack exposes it’s wide, flat bottom to the atmosphere. At an altitude of about 122,000 m (400,000 ft.), the re-entry interface takes place. Here the atmosphere begins to be dense enough for the re-entry phase to begin. From this point, more than 6400 km (4000 mi.) from the runway, the Shuttle will land in about 45 minutes.
The reentry profile has been shown below.
Car crash analysis programs gained wide usage by the late 1980s but ARA (Applied Research Associates) Personnel in the Silicon Valley Office have been engaged in studying the crash response of vehicles, occupant safety, and right-of-way structures since 1971( ARA Website, 25h May). One of the major programs used for this testing is the DYNA3D which was developed at Lawrence Livermore National Laboratory (A Gift of Fire, Baase). DYNA3D is a computer simulation program that models the interactions of physical objects on impact such as vehicle impacts involving roadside structures such as signs, supports, guardrails and crash cushions. DYNA3D, suitable for solving problems involving rapid change, has had many applications in safety analysis. Laboratory analysts have used DYNA3D to study crashworthiness in a number of vehicle safety studies, where models of complex vehicles impact roadside safety structures and other vehicles, deforming under the impact. The DYNA3D program uses a technique called the finite-element method where a grid is superimposed on the frame of a car dividing the car into a finite number of small pieces or elements. The grid is then entered into the program along with data describing the specifications of the materials making up each element such as density, elasticity, etc. While reading the effect of a head-on collision on the structure of the car, the data can be initialized to represent a crash into a wall at a specified speed. The program in return helps compute the force, acceleration, and displacement at each grid point and the stress and strain within each element. Using graphics programs, the simulation produces a picture of the car at intervals after impact.
¨ the pilot tried to send a distress call while he desperately attempted to gain control of the aircraft.
Though a rarity, every once in awhile, planes tend to crash and have serious issues due to problems that could have easily been avoided(183). In the novel the Outliers by Malcolm Gladwell, he explains why planes crash and how it can be prevented. He began this explanation by evaluating different plane crashes from airlines basing from Colombia and Korea. In both events, a series of miniature problems and lack of communication was a cause from the catastrophic events that follow. In the case of the Colombian airlines, the already 14 hours and 40-minute flight(Flight Time) was interrupted by a woman having a stroke causing them to land. Since they did not burn all their fuel, they had to “land heavy” or overweight making the landing much more
The ship was pushing the limits of its engines as it hurtled out of the
Crashworthiness of a material is expressed in terms of its specific energy absorption, Es=F/D, where F is the mean crush stress and D is the density of the composite material. In order to protect passengers during an impact, a structure based on strength and stiffness is far for being optimal. Rather, the structure should collapse in a well defined deformation zone and keep the forces well below dangerous accelerations. However, since the amount of absorbed energy equals the area under the load deflection curve, the two above mentioned criteria are somewhat contradictory, thus showing that, it is not only important to know how much energy is absorbed but also how it is absorbed, i.e., how inertial loads are transferred from impact point to panel supports. Therefore, in addition to designing structures able to withstand static and fatigue loads, structures have to be designed to allow maximum energy absorption during impact.
“Contact the control tower and request an emergency landing at once, clear the runway of any other planes and get the fire emergency team ready at once! We may not be able to control the plane even if we do get it down.”
“Ladies and Gentlemen, we have been cleared for takeoff.” I say into the microphone to warn the passengers and crew about the sudden takeoff. We gain speed and about fifteen seconds later, we get into the air and takeoff. Great takeoff.
Each of NASA’s space exploration projects had many specific goals. The Mercury Project, for example, was designed by scientist to determine human endurance and survival in outer space climate. The
Cars are designed to crumple during a collision as shown in Figure 1. This lengthens the duration of the crash so that the deceleration is less intense. Without crumple zones, the deceleration would be too great for humans and is equivalent to over 15 times what fighter pilots endure during training (MinutePhysics, 2015). Therefore, the longer the duration of the crash, the safer it is for the passengers as there is more time for the vehicle to slow down as demonstrated by Figure 2. There are two types of collisions that a vehicle can incur. Elastic collisions and Inelastic collisions. Elastic collisions are observed in low-speed car carshes where the bumper deforms to absorb the energy and then will pop back out. On the other hand, an inelastic collision is observed through a high-speed car crash in which the bumper would completely crumple to stop the vehicle (Townsend,
as the shuttle can go up to speeds way over 100miles per hour during a
When you leave the aircraft, you are moving horizontally at the same speed as the aircraft, typically 90-110MPH. During the first 10 seconds, a skydiver accelerates up to about 115-130MPH straight down. (A tandem pair uses a drouge chute to keep them from falling much faster than this). It is possible to change your body position to vary your rate of fall.
Human space colonization is quickly becoming one of the main goals and necessities for our species. Although many arguments can be made both in support and against colonization I will try to limit them to just a few basic assumptions.
During impact most of the impact energy in the test specimen is absorbed as plastic deformation when the test specimen yields. Temperature and strain rate effect the yield behaviour and ductility of the material and hence affect the impact energy. Materials that behave this way usually have body-centred cube crystal structures and where lowering the temperature reduces the materials ductility.
I’m doing investigation on defect and failure in the aircraft structures which is important for the prevention of further catastrophic incidents. One of the main reason for the failure of the aircraft components or structure under high stress which is during the operation where the component no longer bear the stress which is imposed.
deal of energy is required, most of which appeared as heat in the target. As a