Hohmann Trajectories

In orbital mechanics, the Hohmann transfer orbit is an elliptical orbit used to transfer between two circular orbit of different altitudes, in the same plane.The orbital maneuver to perform the Hohmann transfer uses two engine impulses, one to move a space craft onto the transfer orbit and a second to move off it.This maneuver was named afterWalter Hohmann, the German scientist220px-Hohmann_transfer_orbit.svg


The diagram shows a Hohmann transfer orbit to bring a spacecraft from a lower circular orbit into a higher one. It is one half of an elliptic orbit that touches both the lower circular orbit that one wishes to leave (labeled 1 on diagram) and the higher circular orbit that one wishes to reach (3 on diagram). The transfer (2 on diagram) is initiated by firing the spacecraft’s engine in order to accelerate it so that it will follow the elliptical orbit; this adds energy to the spacecraft’s orbit. When the spacecraft has reached its destination orbit, its orbital speed (and hence its orbital energy) must be increased again in order to change the elliptic orbit to the larger circular one.

Due to the reversibility orbits, Hohmann transfer orbits also work to bring a spacecraft from a higher orbit into a lower one; in this case, the spacecraft’s engine is fired in the opposite direction to its current path, slowing the spacecraft and causing it to drop into the lower-energy elliptical transfer orbit. The engine is then fired again at the lower distance to slow the spacecraft into the lower circular orbit.

The Hohmann transfer orbit is based on two instantaneous velocity changes. Extra fuel is required to compensate for the fact that the bursts take time; this is minimized by using high thrust engines to minimize the duration of the bursts. Low thrust engines can perform an approximation of a Hohmann transfer orbit, by creating a gradual enlargement of the initial circular orbit through carefully timed engine firings. This requires a change in velocity (delta-v) that is up to 141% greater than the two impulse transfer orbit (see also below), and takes longer to complete.



Advanced Medium Combat Aircraft (AMCA)

The Advanced Medium Combat Aircraft (AMCA), formerly known as the Medium Combat Aircraft (MCA), is a single-seat, twin-engine fifth-generation[2] stealth multirole fighter being developed by India. It will complement the HAL Tejas, the Sukhoi/HAL FGFA, the Sukhoi Su-30MKI and the Dassault Rafale. In February 2013, the Aeronautical Development Agency (ADA) unveiled a 1:8 scale model at Aero India 2013.
Funding and future developments:
In November, 2010, the Aeronautical Development Agency (ADA) sought $2-billion (approximately INR 9,060 crore) of funding for the development of the advanced medium combat aircraft (AMCA). PS Subramanyam subsequently stated, “We have just started working on this fifth-generation aircraft, for which we had already received sanctions to the tune of Rs 100 crore. The way the government is cooperating, I am able to say that we will receive the funding ($2 billion) in the next 18 months.” Funding will initially be utilized to develop two technology demonstrators and seven prototypes. The first flight test was expected to take place by 2017. Currently, the configuration finalization is planned for 2018, with the first flight planned for 2020.
By August 2011, the aircraft was in preliminary design phase. As of July 2012, with aerodynamic design optimisation near complete, the AMCA’s broad specifications are final. The aircraft will have a weight of 16-18 tonnes with 2-tonnes of internal weapons and four-tonnes of internal fuel with a combat ceiling of 15-km, max speed of 1.8-Mach at 11-km. The final design is expected to be shown to the air force by 2012, after which full scale development on the aircraft may start. In February 2013, the Aeronautical Development Agency (ADA) unveiled a 1:8 scale model at Aero India 2013.
The AMCA will be designed with a very small radar cross-section and will also feature serpentine shaped air-intakes, internal weapons and the use of composites and other materials.
As part of the multidisciplinary design optimisation (MDO) currently on for the AMCA—wind-tunnel testing model of the MCA airframe was seen at Aero-India 2009. —that design-based stealth features will include further optimised airframe shaping, edge matching, body conforming antennae and a low IR signature through nozzle design, engine bay cooling and work on reduced exhaust temperature. The aircraft will have an internal weapons bay and radar-absorbent paint and composites.
As well as advanced sensors the aircraft will be equipped with missiles like DRDO Astra and other advanced missiles, stand-off weapons and precision weapons. The aircraft will have the capability to deploy Precision Guided Munitions
General characteristics:

  • Crew: 1 (pilot)
  • Length: 16.5m (Approx.) ()
  • Wingspan: 10.9m (Approx.) ()
  • Height: 5m+ ()
  • Empty weight: N/A ()
  • Powerplant: 2 × GTRE GTX 35 VS Kaveri NG turbofans
  • Dry thrust: 54 kN (12,130 lbf) each
  • Thrust with afterburner: 90 kN (20,230 lbf) each


  • Maximum speed: Mach 1.8+
  • Range: 1000 km + ()
  • Service ceiling: 15,000+ ()
  • Rate of climb: N/A ()