The flight path of the planetary probe is calledroute(or track).To fly to otherscelestial bodiesMust be able to get rid of the gravity of the earthSecond cosmic speed, the aircraft flies away from the earth in a parabolic trajectory, and then flies around the sun in a circular orbit under the action of solar gravity.If it is greater thanSecond cosmic speedAnd less thanThird cosmic speedAlong the earthrevolutionDirection flight, because it is faster than the speed required to fly around the sunPerihelionAfter entering orbit, it will fly around the sun in an elliptical orbit outside the earth orbit.The greater the speed, the longer the elliptical orbit, and the farther the distance to reach.Therefore, different initial velocities can make the detector reachMars、Jupiter……PlutoExtraterrestrial planets and their moons.If it flies in the opposite direction of the earth's revolution, the detector will fly around the sun in the elliptical orbit inside the earth's orbit under the action of the sun's gravity after entering the orbit at the aphelionVenus、Mercuryetc.Terrestrial planetMeet.If it reachesThe Third UniverseSpeed, then it takeshyperbolaThe orbit flies away from the earth and away from the sun in a parabola.If the launch time is appropriate, it can also meet the exoplanet.
It can be seen from the above that there is more than one route (orbit) to other celestial bodies in the solar system.Since the initial speeds required by various orbits are different, and the minimum initial speed is the most energy saving orbit, the orbit with the minimum initial speed is called the orbit with the least energy.
Fly toplanetThere is only one route with the least energy, which is a double tangent elliptical orbit that is tangent to the Earth orbit and the target planet orbit at the same time.It was first proposed by Austrian scientist Horman in 1925, so it is also called“Hohmann trajectory ”[2]。The Hohmann orbit focuses on the sun,Apohelion(orPerihelion）And perihelion (or aphelion) are located in Earth orbit and target planet orbit respectively.The major axis of the orbit is equal to the sum of the earth's orbit radius and the orbit radius of the target planet.
It takes too long to fly to a distant planet with the most energy saving route, such asPlutoIt will take about 46 years.In order to save time, it is necessary to use other routes, or use self powered acceleration during the voyage, or use the gravity of other planets to accelerate, but in this way, its trajectory is no longer a simple ellipse, parabola or hyperbola.The route to the moon is similar to that to the planet.
In practical applications, in order to overcome the limitation of the geographical location of the rocket launch site, the probes flying to the moon and planets generally enter the transition orbit around the earth first, and then accelerate into the predetermined route at the appropriate orientation.
American space probe
Announce
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Witness the historical moment
Lunar rover
In the process of landing on January 3, Spirit, with air bag protection, approached Mars at a speed of 19000 kilometers per hour, and then used heat protection devicesparachuteAnd reverse propulsion rockets.After initial contact with the surface of Mars, the probe jumped and rolled for several minutes, and was finally fixed on the landing platform in Gusev crater.The meteorite crater was chosen as the landing site because scientists believe that it may have been a lake in ancient times.
Venus probe
Director of NASASean O'Keefe(Sean O'Keefe) After the radio signal confirmed that Spirit had successfully landed, he said: "Tonight is worth celebrating. We are back... we have landed on Mars!"
Another NASA Mars rover“Opportunity”It has also been launched and will be launched on January 25Red PlanetThe other side of the landing.
Three hours after landing, Spirit sent pictures back to Earth through the orbiting NASA Odyssey Mars probe.The space agency said in another press release,Meteorite craterThe landforms of the space agency are similar to those of the other three probes successfully launched to Mars in the past“Viking ”(Viking) and“Pathfinder”(Pathfinder)。)The landforms of the surveyed sites are different.In 1999, the first generation of probes launched by the United States to explore Mars were lost.
The principal investigator of the detectorCornell UniversitySteve Squyres of Mars said: "The types of rocks we see are different from the materials we see elsewhere on Mars." In addition, he said that the wind and dust storms at the landing site seem to have swept away most of the dust deposits covered on the surface of Mars, and the exposed rocks can be used by the probe's geological instruments for sampling investigation.
Its mission
The mission of Spirit is to explore the rocks and soils around the crater in the next three months. These rocks and soils may indicate whether the past ecological environment around the crater waswaterAnd suitable forlifeExists.According to the data collected by the Mars orbiter, Gushev Crater may have been a lake in ancient times.One is obviously long and deep after water erosionmountain valleyIt extends into Gusev crater.Meteorite crater is about 13000 square kilometers, which was formed by asteroids orcometIt is made by impact.
Before the Spirit goes down from the landing platform to the land surface, the flight team of the space agency is expected to spend more than a week testing various mechanisms of the probe.At the same time, the Spirit's camera will begin to take pictures of the surrounding terrain."Spirit" was launched from Cape Canaveral, Florida on June 10, and reached Mars after a flight of 487 million kilometers.[3]
