Spacecraft propulsion refers to how a space vehicle achieves forward movement. As there is no medium in space such as air, wings and fins are ineffective at maneuverability; electric thrusters may provide assistance instead.
A rocket propels itself by pushing on the gas that ignites from its engines – this is a straightforward scientific fact based on Newton’s laws of motion.
Rocket Propulsion
Rockets propel themselves forward by using different forces than those found on Earth to overcome gravity’s pull on them, such as using their exhaust gases to generate an unbalanced force that propels them. As there is no friction in space, rockets must use other means to propel themselves. As there is no friction to act against, other means must be utilized such as exhaust gases to provide propulsion. To be successful at doing so.
Thrust is the force exerted by rocket propulsion systems to move gas forward with force, measured in terms of specific impulse. The specific impulse measures the speed at which gas leaves the rocket. This depends on various factors including fuel and oxidizer proportions, engine size/shape/efficiency/combustion efficiency as well as nozzle geometry.
Current NASA space vehicles use chemical rocket engines, but many are nearing the end of their operational lives and new propulsion systems are needed to extend popular programs such as Kepler Space Telescope which ran out of its propellant supply in 2014. Going forward, NASA plans on using electric propulsion (EP) technologies instead.
Ion Propulsion
Ion propulsion employs propellant gas (usually xenon) combined with an electric field to generate thrust. Ions are produced by bombarding the propellant gas with electrons from a hot cathode filament; these electrons remove electrons from atoms leaving positively charged ions which are extracted using multiple-aperture grids and then accelerated using potential differences to generate high exhaust velocity for added thrust.
Ion engines can operate for much longer than chemical systems, gradually accelerating spacecraft over days or weeks. They allow spacecraft to achieve very high acceleration velocities and shorten long-distance interplanetary missions by using these long-lasting engines – as evidenced by Dawn using them to transition from its launch orbit into orbit around Vesta and Ceres – something conventional technologies would never allow – while BepiColombo plans on employing them during both of its Venus swingbys.
Lithium-Ion Batteries
Lithium-ion batteries (LIBs) are rechargeable cells made up of lithium compounds. When charged, lithium ions move from anode to cathode electrode and create a potential difference which generates current. When discharged, this current is converted to energy in form of current.
Li-ion batteries are lightweight and have twice the energy density of nickel-cadmium. Furthermore, their self-discharge rate is reduced and no harmful fumes, liquids or gases are produced during discharge or charge cycles.
Maintenance-free lithium and lithium-ion batteries can help facilities save operational costs by eliminating the need for regular discharge/charge cycles. Unlike alkaline batteries, however, lithium and lithium-ion batteries cannot be safely disposed of through trash or recycling carts; rather they must remain inside products where their presence could potentially cause an immediate fire or explosion if forcible removal were attempted. Several chemistries exist such as nickel manganese cobalt (NMC) and lithium iron phosphate (LFP); both offer safety features to protect against overdischarge or overcharging of their respective batteries.
Solid Propellants
Solid propellant provides rockets with their main source of thrust. Composed of black powder fuel and an oxidizer mixed in an enclosed cylinder, its hole serves as the combustion chamber where its contents burn at high temperatures and pressures, producing thrust that allows rockets to escape Earth’s atmosphere.
This type of rocket motor is the same one seen on model rockets and air-to-air missiles, providing mechanical simplicity over liquid propellant engines which require additional support equipment and take longer to load ready for launch. They’re also more durable, as they can be stored for extended periods loaded and ready to go!
HISP will enhance European space industry competitiveness and enable greater scientific return from future space exploration missions by significantly decreasing time, cost and mass requirements to reach their destination. This will increase our knowledge of solar system, universe and ultimately ourselves.