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It is true that there is practically no air to be pushed back to get a force in the forward direction, as in the case of a boat. In rockets, the force is generated as the reaction to the mass expelled from the rocket engine itself at very high velocity. Hence no support from anything outside is required to sustain accelerated flight. Such systems are called reactive propulsion systems.

When an upper rocket stage has finished its operation, remaining fuel and batteries in it are discharged. This procedure is called passivation. This ensures that there is reduced risk even if the stages continue in orbit. Large stages, however re enter the atmosphere over the course of time and burn up . In some other cases upper stages are deliberately pushed back into the atmosphere to make up burned up. This process is often called de-boosting.

Contrary to what is often portrayed, there is no gold covering on the satellite. Those gold-colored foils are MLI – Multi layer insulation sheets which are used to for thermal protection as the satellite is exposed to extremes of temperatures while in orbit. The amber colored Kapton sheets over the silver aluminized mylar gives the gold color to MLI. It is primarily used to reduce radiative heat transfer between the satellite and deep space.

A black hole is an entity formed when a really huge star collapses, towards the end of its active life. Once its hydrogen fuel in a star is fully consumed, there is nothing to oppose its gravitational force and it implodes under its own weight. Everything around a black hole is sucked into it, like water is drawn to a hole on ground. The force of gravity in a black hole is so strong that nothing can practically escape from it – not even light particles

The life span of a satellite is typically 10-15 years.

Life support system on space stations provide oxygen from storage gas bottles. There are various methods by which oxygen is regenerated as well. By electrolysis of water oxygen can be generated and so with many other form of chemical processes.

Yes, contrary to many conspiracy theories floating around, humans have indeed landed on the moon between 1969 and 1972. All arguments otherwise have been exposed and debunked countless times

Rockets, as you know are used to take satellites to orbit through predefined path called trajectories. To control a rocket is to make it follow its path against both internal and external disturbing forces. To do the same, we must first know the rocket’s present position at that instant of time. Sensors help us in determining the current position and attitude of the rocket and thereby its deviation from the expected path, if any. This error must be corrected by using various actuators. They control the direction of the rocket by controlling the direction of thrust developed by the rocket engine

If a rocket goes out of control, all efforts will be done using actuators to bring it back to its regular path. If all other option fails, the rockets can be remotely command to destroy itself using explosive systems specially provided for the purpose.

The fuel and oxidizer combination in rockets have to be highly energy rich and should give out high temperature gases at very high rate. Conventional fuels like gasoline are not just powerful enough for efficient use in rocket engines

The activities connected with assembly and launch of a rocket is generally listed down in detail with respect to time. For such activities the clock is counted backwards. The lift off event is marked at T=0 and the other activities are sequenced with respect to that. For example, if the propellant filling is started 24 hours before lift off, it is designated as T minus 24 hours and so on. The last seconds upto the lift off generally read out aloud and represents the most exciting time period and a befitting build up to the lift off.

Modern rockets are very complex and often may contain lakhs of components. The entire systems may take years to fabricate, build and assemble. Once all major hardware and software are available, the final integration of the rocket may typically take between 1-2 months

The tile like elements which seem to fall during PSLV launch are nothing but the thermal protection pads intentionally discarded. The second stage of PSLV uses propellants which have to be insulated from external heat during launch pad operations. Hence it is protected during that time. However, this becomes an unnecessary dead weight after this phase. Hence it is jettisoned immediately after liftoff

The international space station (ISS) is a joint venture of five space agencies. The individual modules are built by the respective organisations, launched from different launch pads and then assembled in space. As on date, there are 14 major modules in ISS. The first module of ISS was Zarya, of the Russian Space agency and was launched in 1998 by a Proton rocket.

As per the latest scientific observations and studies, the earth is almost four and a half billion years old. The first primitive form of life started appearing within the first billion years or so.

Just like automobiles are desired to travel on different lanes in a road, satellite orbits are also selected so as to avoid any close encounter. These have to be approved by appropriate International authorities as well.

Yes and it is a real threat. This is addressed by constant monitoring of spece debris and their path. There are catalogues which track anyorbiting objects larger than 10cm diameter. The orbits of these objects are predicted and their possibility of collision with any other useful space object is estimated. For critical objects like the ISS and serving satellites, evaluations are constantly made to assess if there is any orbiting object in their vicinity. Once it is found to be any risk of collision, then the orbit of the ISS/serving satellites is adjusted to avoid collision

As the name suggests, space shuttle, was used to ‘shuttle’ or move to and fro from orbit to ground and vice versa. The orbiter of the space shuttle system was reusable and hence can repeatedly carry astronauts and supplies from earth to orbit and back. Whereas, rockets are mostly staged vehicles which expend their used stages and hence are one way – to orbit and cannot be reused to bring spacecrafts/people from orbit to earth. However, there are rockets now such as falcon which reuse the initial stages. The space shuttle fleet was retired in 2011.

A number of rockets have been used to send humans to space. The rocket which was used to send Yuri Gagarin to orbit was called R-7 “Semyorka”- Vostok. Atlas was used by Americans for their early human spaceflight missions. Saturn 1B and Titan were also used by USA in the sixties and seventies. The apollo missions which carried humans to moon used the gigantic Saturn V Rockets. Soyuz rocket remained the mainstay of Soviet and later Russian human spaceflight missions. China uses long march rockets and quite recently Falcon 9 by SpacEX is used for ferrying astronauts to ISS.

A main function of the rocket is to carry satellites and place it in orbit. A satellite can remain in orbit only if maintains a fixed velocity, approximately equal to 7.8Km/s for a low earth orbit. Hence the rocket must be able to provide 7.8Km/s. However, for rockets that go beyond earth orbit, it must achieve escape velocity of 11.8 Km/s. Thus the mission of the rocket is adjusted so that the required velocity can be achieved.

As on today, rockets are the only mode of putting satellites into orbit. Many concepts such as space elevators, laser and electro magnetic propulsion, space guns etc. are discussed but none of them have been demonstrated