question: If the meteors are disintegrated as they enter the atmosphere, how can spacecrafts get in and out of the atmosphere?
comment: They have a heat shield that faces the direction of atmosphere entry that protects the craft. One kind previously used was called an ablative heat shield, which effectively slowly disintegrated, taking heat with it as it does. These days it's mostly based on a thermal insulator. Without a heat shield, many crafts would be destroyed on reentry.
passages: For Earth, atmospheric entry occurs at the Kármán line at an altitude of 100 km (62.14 mi / ~ 54 nautical mi) above the surface, while at Venus atmospheric entry occurs at 250 km (155.3 mi / ~135 nautical mi) and at Mars atmospheric entry at about 80 km (50 mi / ~ 43.2 nautical mi). Uncontrolled, objects reach high velocities while accelerating through space toward the Earth under the influence of Earth's gravity, and are slowed by friction upon encountering Earth's atmosphere. Meteors are also often travelling quite fast relative to the Earth simply because their own orbital path is different from that of the Earth before they encounter Earth's gravity well. Most controlled objects enter at hypersonic speeds due to their suborbital (e.g., intercontinental ballistic missile reentry vehicles), orbital (e.g., the Soyuz), or unbounded (e.g., meteors) trajectories. Various advanced technologies have been developed to enable atmospheric reentry and flight at extreme velocities. An alternative low-velocity method of controlled atmospheric entry is buoyancy which is suitable for planetary entry where thick atmospheres, strong gravity, or both factors complicate high-velocity hyperbolic entry, such as the atmospheres of Venus, Titan and the gas giants.
   "Atmospheric entry" is the movement of human-made or natural objects as they enter the atmosphere of a celestial body from outer space—in the case of Earth from an altitude above the Kármán Line, (100 km). This topic is heavily concerned with the process of controlled "re"entry of vehicles which are intended to reach the planetary surface intact, but the topic also includes uncontrolled (or minimally controlled) cases, such as the intentionally or circumstantially occurring, destructive deorbiting of satellites and the falling back to the planet of "space junk" due to orbital decay.
  
  Section::::See also.
  
  BULLET::::- Orbital mechanics
  
  Section::::References.
   BULLET::::- Soyuz TMA-11 – The Soyuz propulsion module failed to separate properly; fallback ballistic reentry was executed that subjected the crew to accelerations of about . The crew survived.
  
  Section::::Uncontrolled and unprotected reentries.
  
  Of satellites that reenter, approximately 10–40% of the mass of the object is likely to reach the surface of the Earth. On average, about one catalogued object reenters per day.
   Because of the increasing number of objects in space, NASA has adopted guidelines and assessment procedures to reduce the number of non-operational spacecraft and spent rocket upper stages orbiting the Earth. One method of postmission disposal is to allow reentry of these spacecraft, either from orbital decay (uncontrolled entry) or with a controlled entry. Orbital decay may be achieved by firing engines to lower the perigee altitude so that atmospheric drag will eventually cause the spacecraft to enter. However, the surviving debris impact footprint cannot be guaranteed to avoid inhabited landmasses. Controlled entry normally occurs by using a larger amount of propellant with a larger propulsion system to drive the spacecraft to enter the atmosphere at a steeper flight path angle. It will then enter at a more precise latitude, longitude, and footprint in a nearly uninhabited impact region, generally located in the ocean.
   These objects are "leaving" the Solar System because their velocity and direction are taking them away from the Sun, and at their distance from the Sun, its gravitational pull is not sufficient to pull these objects back or into orbit. They are not impervious to the gravitational pull of the Sun and are being slowed down, but they have enough velocity to coast into interstellar space, i.e. retaining sufficient escape velocity to leave the Solar System.
  
  Section::::Planetary exploration probes.
   Every planetary probe was placed into its escape trajectory by a multistage rocket, the last stage of which ends up on nearly the same trajectory as the probe it launched. Because these stages cannot be actively guided, their trajectories are now different from the probes they launched (the probes were guided with small thrusters that allow course changes). However, in cases where the spacecraft acquired escape velocity because of a gravity assist, the stages may not have a similar course and there is the remote possibility that they collided with something. Some objects in heliocentric orbit have been reidentified with a telescope, and so their trajectories can be confirmed. The stages on an escape trajectory are:
   where the product "G" "M" is the heliocentric gravitational parameter. The initial speed required to escape the Sun from its surface is , and drops down to at Earth's distance from the Sun (1 AU), and at a distance of 100 AU.
  
  Section::::Propulsion stages.
   The third stage of "Pioneer 11" is thought to be in solar orbit because its encounter with Jupiter would not have resulted in escape from the Solar System. "Pioneer 11" gained the required velocity to escape the Solar System in its subsequent encounter with Saturn.
  
  The only objects to date to be launched directly into a solar escape trajectory were the "New Horizons" spacecraft, its third stage, and the two de-spin masses. The "New Horizons" Centaur (second) stage is not escaping; it is in a 2.83-year heliocentric (solar) orbit.
   Vehicles sent on lunar or planetary missions are generally not launched by direct injection to departure trajectory, but first put into a low Earth parking orbit; this allows the flexibility of a bigger launch window and more time for checking that the vehicle is in proper condition for the flight. A popular misconception is that escape velocity is required for flight to the Moon; it is not. Rather, the vehicle's apogee is raised high enough to take it to a point (before it reaches apogee) where it enters the Moon's gravitational sphere of influence (though the required velocity is close to that of escape.) This is defined as the distance from a satellite at which its gravitational pull on a spacecraft equals that of its central body, which is
   Once in orbit, their speed keeps them in orbit above the atmosphere. If e.g., an elliptical orbit dips into dense air, the object will lose speed and re-enter (i.e. fall). Occasionally a space craft will intentionally intercept the atmosphere, in an act commonly referred to as an aerobraking maneuver
  
  Section::::Newton's laws of motion.
  
  Section::::Newton's laws of motion.:Newton's law of gravitation and laws of motion for two-body problems.
   Atmospheric entry
  
  Atmospheric entry is the movement of an object from outer space into and through the gases of an atmosphere of a planet, dwarf planet, or natural satellite. There are two main types of atmospheric entry: uncontrolled entry, such as the entry of astronomical objects, space debris, or bolides; and controlled entry (or reentry) of a spacecraft capable of being navigated or following a predetermined course. Technologies and procedures allowing the controlled atmospheric entry, descent, and landing of spacecraft are collectively termed as EDL.
   Even in the case of an airless body, there is a limit to how close a spacecraft may approach. The magnitude of the achievable change in velocity depends on the spacecraft's approach velocity and the planet's escape velocity at the point of closest approach (limited by either the surface or the atmosphere.)
   Eleven essentially similar empty S-IVB stages from Apollo, Skylab and Apollo-Soyuz Test Project missions have re-entered the atmosphere from 1966–1975. In all cases (including the Skylab station), the objects burned in the atmosphere and broke into relatively small pieces, rather than striking the Earth as a single mass. On the other hand, these objects entered from low Earth orbit or ballistic trajectory, with less energy than J002E3 might possibly have if it were to enter from Solar orbit.
  
  Section::::See also.
  
  BULLET::::- 6Q0B44E, space debris originally thought to be a meteoroid
   When atmospheric entry is part of a spacecraft landing or recovery, particularly on a planetary body other than Earth, entry is part of a phase referred to as "entry, descent, and landing", or EDL. When the atmospheric entry returns to the same body that the vehicle had launched from, the event is referred to as reentry (almost always referring to Earth entry).
  
  Section::::Entry vehicle shapes.
  
  There are several basic shapes used in designing entry vehicles:
  
  Section::::Entry vehicle shapes.:Sphere or spherical section.
   For interplanetary travel, a spacecraft can use its engines to leave Earth's orbit. It is not explicitly necessary as the initial boost given by the rocket, gravity slingshot, monopropellant/bipropellent attitude control propulsion system are enough for the exploration of the solar system (see New Horizons). Once it has done so, it must somehow make its way to its destination. Current interplanetary spacecraft do this with a series of short-term trajectory adjustments. In between these adjustments, the spacecraft simply moves along its trajectory with a constant velocity. The most fuel-efficient means to move from one circular orbit to another is with a Hohmann transfer orbit: the spacecraft begins in a roughly circular orbit around the Sun. A short period of thrust in the direction of motion accelerates or decelerates the spacecraft into an elliptical orbit around the Sun which is tangential to its previous orbit and also to the orbit of its destination. The spacecraft falls freely along this elliptical orbit until it reaches its destination, where another short period of thrust accelerates or decelerates it to match the orbit of its destination. Special methods such as aerobraking or aerocapture are sometimes used for this final orbital adjustment.
   For example, Mars Pathfinder entered in 1997. About 30 minutes prior to entry, the cruise stage and entry capsule separated. When the capsule hit the atmosphere it de-accelerated from about 7.3 km/s to 0.4 km/s (16330 mph to 900 mph) over three minutes. As it descended the parachute opened to slow it down further, and soon after the heat shield was released. During entry a signal was relayed back to Earth, including semaphore signals for important events.
  
  Section::::List of spacecraft.
  
  Some examples of spacecraft that have attempted to land on the surface of Mars:
  
  BULLET::::- Mars 2 (lost)
  
  BULLET::::- Mars 3 (lost)
   Ballistic warheads and expendable vehicles do not require slowing at reentry, and in fact, are made streamlined so as to maintain their speed. Furthermore, slow-speed returns to Earth from near-space such as parachute jumps from balloons do not require heat shielding because the gravitational acceleration of an object starting at relative rest from within the atmosphere itself (or not far above it) cannot create enough velocity to cause significant atmospheric heating.
   On a sub-orbital spaceflight the spacecraft reaches space and then returns to the atmosphere after following a (primarily) ballistic trajectory. This is usually because of insufficient specific orbital energy, in which case a suborbital flight will last only a few minutes, but it is also possible for an object with enough energy for an orbit to have a trajectory that intersects the Earth's atmosphere, sometimes after many hours. Pioneer 1 was NASA's first space probe intended to reach the Moon. A partial failure caused it to instead follow a suborbital trajectory to an altitude of before reentering the Earth's atmosphere 43 hours after launch.
   Space debris and meteoroids can impact spacecraft at high speeds, causing mechanical or electrical damage. The average speed of space debris is 10 km/s while the average speed of meteoroids is much greater. For example, the meteoroids associated with the Perseid meteor shower travel at an average speed of 58 km/s. Mechanical damage from debris impacts have been studied through space missions including LDEF, which had over 20,000 documented impacts through its 5.7 year mission. Electrical anomalies associated with impact events include ESA's Olympus spacecraft, which lost attitude control during the 1993 Perseid meteor shower. A similar event occurred with the Landsat 5 spacecraft during the 2009 Perseid meteor shower.
   On a sub-orbital spaceflight, a space vehicle enters space and then returns to the surface, without having gained sufficient energy or velocity to make a full orbit of the Earth. For orbital spaceflights, spacecraft enter closed orbits around the Earth or around other celestial bodies. Spacecraft used for human spaceflight carry people on board as crew or passengers from start or on orbit (space stations) only, whereas those used for robotic space missions operate either autonomously or telerobotically. Robotic spacecraft used to support scientific research are space probes. Robotic spacecraft that remain in orbit around a planetary body are artificial satellites. To date, only a handful of interstellar probes, such as "Pioneer 10" and "11", "Voyager 1" and "2", and "New Horizons", are on trajectories that leave the Solar System.
   Meteoroids travel around the Sun in a variety of orbits and at various velocities. The fastest move at about through space in the vicinity of Earth's orbit. This is escape velocity from the Sun, equal to the square root of two times Earth's speed, and is the upper speed limit of objects in the vicinity of Earth, unless they come from interstellar space. Earth travels at about , so when meteoroids meet the atmosphere head-on (which only occurs when meteors are in a retrograde orbit such as the Eta Aquariids, which are associated with the retrograde Halley's Comet) the combined speed may reach about (see Specific energy#Astrodynamics). Meteoroids moving through Earth's orbital space average about .
   BULLET::::- Atmospheric entry — is the movement of an object from outer space into and through the gases of an atmosphere of a planet, dwarf planet or natural satellite. There are two main types of atmospheric entry: uncontrolled entry, such as the entry of astronomical objects, space debris or bolides; and controlled entry (or reentry) of a spacecraft capable of being navigated or following a predetermined course. Technologies and procedures allowing the controlled atmospheric entry, descent and landing of spacecraft are collectively termed as EDL.
   The "Pioneer 10" and "11", and "Voyager 1" and "2" Centaur (second) stages are also in heliocentric orbits.
  
  In order to leave the Solar System, the probe needs to reach the escape velocity. After leaving Earth, the Sun's escape velocity is 42.1 km/s. In order to reach this speed, it is highly advantageous to use the orbital speed of the Earth around the Sun, which is 29.78 km/s. By passing near a planet, a probe can gain extra speed.
   The escape velocity from the Earth's surface is about 11 km/s, but that is insufficient to send the body an infinite distance because of the gravitational pull of the Sun. To escape the Solar System from a location at a distance from the Sun equal to the distance Sun–Earth, but not close to the Earth, requires around 42 km/s velocity, but there will be "partial credit" for the Earth's orbital velocity for spacecraft launched from Earth, if their further acceleration (due to the propulsion system) carries them in the same direction as Earth travels in its orbit.
   When meteoroids intersect with Earth's atmosphere at night, they are likely to become visible as meteors. If meteoroids survive the entry through the atmosphere and reach Earth's surface, they are called meteorites. Meteorites are transformed in structure and chemistry by the heat of entry and force of impact. A noted asteroid, , was observed in space on a collision course with Earth on 6 October 2008 and entered Earth's atmosphere the next day, striking a remote area of northern Sudan. It was the first time that a meteoroid had been observed in space and tracked prior to impacting Earth. NASA has produced a map showing the most notable asteroid collisions with Earth and its atmosphere from 1994 to 2013 from data gathered by U.S. government sensors (see below).
  
presuppositions: Spacecrafts should disintegrate when they enter the atmosphere, since meteors do.
corrections: Spacecrafts have a heat shield that protects the craft during atmosphere entry.
raw_presuppositions: Spacecrafts should disintegrate when they enter the atmosphere, since meteors do. Spacecrafts should disintegrate when they enter the atmosphere  since meteors do.
raw_corrections: Spacecrafts have a heat shield that protects the craft during atmosphere entry. Spacecrafts have a heat shield that protects the craft during atmosphere entry.