HELIUM
1. Context
Two NASA astronauts aboard Boeing’s Starliner will stay on the International Space Station for months because of a faulty propulsion system whose problems included helium leaks.
2. Helium
Source: Britannica
Helium is a chemical element with the symbol He and atomic number 2. It is a colorless, odorless, tasteless, non-toxic, and inert gas that belongs to the noble gas group in the periodic table. Helium is the second most abundant element in the universe after hydrogen.On Earth, it is relatively rare. It is mainly extracted from natural gas fields, especially in the U.S., Qatar, and Algeria.
Properties:
- Atomic number: 2
- Atomic mass: 4.0026 u
- Density: Very low (lighter than air)
- Boiling point: -268.93°C (4.22 K)
- Melting point: It doesn't solidify at normal pressure, even at absolute zero; it requires high pressures to become solid.
3.Why do spacecraft and rockets use helium?
Helium is chemically inert, meaning it doesn't react with other materials or ignite, and with an atomic number of 2, it's the second lightest element, just after hydrogen. Rockets must reach specific speeds and altitudes to enter and stay in orbit. A heavier rocket requires more energy, which leads to increased fuel consumption and the need for more powerful, expensive engines to develop, test, and maintain.
With an extremely low boiling point of –268.9°C, helium stays in a gaseous state even in extremely cold environments, making it ideal for use with rocket fuels stored at such temperatures
4. Applications of Helium in Aerospace
Helium is used in spacecraft and rockets primarily because of its inert nature, lightweight properties, and resistance to freezing or liquefying under extreme conditions.
Here are the key reasons why helium is so important in these aerospace applications:
- In rockets, liquid fuel and oxidizer are stored at extremely low temperatures to maintain them in liquid form (cryogenic fuels like liquid hydrogen and liquid oxygen). As these liquids are consumed during flight, the tanks need to be pressurized to maintain a constant flow of fuel to the engines.
- Helium is ideal for this because it is inert and will not react with the highly volatile rocket fuels. It is also light enough to minimize the impact on the rocket's overall weight, which is crucial in space missions
- Helium is used to purge (clean out) fuel lines and tanks of spacecraft to remove any traces of reactive chemicals, ensuring that the next fuel load is uncontaminated.
- Before and after launch, helium is pumped through the system to remove residual fuel or oxidizer, thus avoiding the risk of combustion or explosion. Since helium is inert, it doesn't react with the materials or chemicals used in rockets
- In liquid-fueled rockets, cryogenic propellants like liquid hydrogen and liquid oxygen are used, which must be kept at very low temperatures. Helium is used to pressurize and transfer these cryogenic propellants because it remains gaseous even at very low temperatures and does not solidify or become too dense under extreme conditions.
- Some rocket stages use helium to inflate tanks and assist in separation of stages during flight. For example, when the first stage of a rocket has burned its fuel, helium is pumped into the tank to pressurize it, ensuring proper separation between the stages
- Helium is also used in spacecraft cooling systems, especially in scientific equipment that requires precise temperature control, such as in satellite instruments or space observatories. For example, the James Webb Space Telescope uses helium to cool its infrared detectors
- Helium’s low density and non-flammable nature make it easy to store in high-pressure gas bottles, which are used to pressurize various systems on rockets. Helium is stored in compact, lightweight containers, which are critical in reducing the overall mass of the spacecraft
5. How is helium used in spacecraft?
Helium is employed to pressurize fuel tanks, ensuring a steady flow of fuel to the rocket’s engines. It is also used in cooling systems. As the rocket’s engines burn fuel and oxidizer, helium fills the empty space in the tanks to maintain consistent internal pressure.
Due to its inert nature, helium can safely interact with any residual substances left in the tanks without causing reactions
Here are the primary ways helium is used in spacecraft:
- Helium is used to maintain pressure in the spacecraft's fuel and oxidizer tanks. As the liquid propellants are consumed during a mission, helium is introduced into the tanks to keep the pressure stable, ensuring a smooth flow of fuel to the engines. Its light weight and non-reactive nature make it an ideal choice for this purpose
- Before launch and after certain operations, helium is used to purge fuel lines and tanks to remove residual chemicals, preventing contamination or unwanted reactions. This is important for maintaining the spacecraft's safety and ensuring the integrity of the propulsion system
- Spacecraft often use cryogenic fuels like liquid hydrogen and liquid oxygen, which are stored at extremely low temperatures. Helium is used to pressurize these cryogenic systems because it remains in a gaseous state at very low temperatures, avoiding freezing and ensuring consistent pressure
- During multi-stage rocket launches, helium is sometimes used to pressurize the tanks in between rocket stages, aiding in the smooth separation of stages. This helps to reduce risks during the transition between stages in flight
- Helium is also used to cool sensitive equipment on spacecraft, such as infrared detectors or scientific instruments, which need to be maintained at very low temperatures. For instance, space telescopes and observation satellites use helium to cool their sensors and other components
- Helium is part of the environmental control systems on spacecraft, helping to regulate pressure in sealed compartments or manage gases during space missions
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For Prelims: PSLV, GSLV, GSLV Mk-III, SSLV
For Mains: GS III- Science & Technology- Satellite Applications, Challenges and Solutions
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Previous Year Questions
1. With reference to India's satellite launch vehicles, consider the following statements: (UPSC 2018)
1. PSLVs launch satellites useful for Earth resources monitoring whereas GSLVs are designed mainly to launch communication satellites.
2. Satellites launched by PSLV appear to remain permanently fixed in the same position in the sky, as viewed from a particular location on Earth.
3. GSLV Mk III is a four- staged launch vehicle with the first and third stages using solid rocket motors; and the second and fourth stages using liquid rocket engines.
Which of the statements given above is/are correct?
A. 1 only
B. 2 and 3
C. 1 and 2
D. 3 only
Answer: A
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Source: Indianexpress
