Correct Answer :
Explanation : Phasing maneuver is a used when a spacecraft in a given orbit is moved to a different location within the same orbit. This is carried out using two-impulse Hohmann transfer. The first burn is carried out in the original orbit to shrink or expand the orbit. On completing the orbit and returning to the original burn point, it performs second maneuver.
Correct Answer : To adjust the inclination angle of the orbit
Explanation : The phasing maneuver is usually carried out when the spacecraft needs to rendezvous ahead or behind another spacecraft. Also, sometimes this is carried out to save the fuel by entering a phasing orbit closer the original orbit and performing multiple orbits before returning back to the orbital burn point.
Correct Answer : ΔV = v2 – v1
Explaination : In order to calculate the total impulse which is required by the space shuttle/ satellite to change its position from initial orbit to phasing orbit, ΔV = v2 – v1 is used.Where, v1 is the spacecraft’s velocity at point of intersection in original orbitv2 is the spacecraft’s velocity at point of intersection in phasing orbit.
Correct Answer : Speed up
Explanation : If the target is behind the interceptor in the same orbit, the interceptor must speed up to enter a higher, slower orbit thereby allowing the target to catch up.
Correct Answer : High energy orbit
Explanation : For military operation mission, more energy is required than what is required for the Hohmann transfer. High energy orbit is used when transfer time is of the essence. In this operation, an impulse is given at the initial circular orbit which pushes the spacecraft into an elliptical orbit. After reaching the desired point, another small impulse is given to circularize the orbit and place the spacecraft at the desired altitude.
Correct Answer : Electric propulsion transfer
Explanation : In case of electric propulsion transfer, the final orbit is reached by spiraling outward as there is less consumption of propellant due to the high Isp value of the electric propulsion.
Correct Answer : Speed down
Explanation : To catch a spacecraft ahead of it in the same orbit, the interceptor slows down, entering a smaller phasing orbit with a shorter period. This allows it to catch the target and go ahead of it.
Correct Answer : 2
Explanation : Non-Hohmann transfer makes use of two impulses. The first impulse is made at the initial orbit which helps in entering the transfer orbit. After that, a second impulse is applied to enter the final orbit.
Correct Answer : Imaginary line connecting the apsides of ellipse
Explanation : Apse line is the imaginary line that connects the two extreme apside points in the orbit. It is only defined for elliptic parabolic or hyperbolic orbits as the circular orbit has an eccentricity of 0. For the Non-Hohmann transfer, the two orbits share a common apse line.
Correct Answer : η = θ1 – θ2
Explaination : The rotation of the line of apsides is given as the difference between the true anomalies of the point of intersection as measured from the periapsis of the orbit. This can ben seen in the figure below.
Correct Answer : Transfer shares the apse line to both the orbits
Explanation : In both Hohmann and Non-Hohmann transfers, there’s a transfer between the two co-axial elliptical orbits. The main difference is that in Hohmann transfer, the transfer trajectory is tangent to both the initial and final orbits, whereas in Non-Hohmann that is not true. In the later case, both the orbits share a common apse line.
Correct Answer : Lambert’s problem
Explanation : Chase maneuvers are solved using Lambert’s problems. In chase maneuver, there are two spacecrafts which orbit in two non-coplanar elliptic orbits. One of the spacecraft tries to intercept the another one. This intercept trajectory is bi-elliptic orbital transfer.
Correct Answer : False
Explanation : Chase maneuvers are considered to be energy demanding maneuvers which involves one spacrcraft trying to intercept the other spacecraft using bi-elliptic transfer orbit.
Correct Answer : LEO
Explanation : Chase maneuvers are considred to be impractical for Low Earth orbits as they are very energy demanding with high delta-v requirements. They are usually carried out for interplanetary missions.
Correct Answer : Chase
Explanation : In case of chase maneuver, there are two spacecrafts involvolved in which one spacecraft chases the other. The term used for this spacecraft is ‘Chase’.
Correct Answer : Target
Explanation : When two spacecrafts are orbiting in a rendezvous, and one spacecraft tries to intercept the other spcecraft, the maneuvering spacecraft is known as ‘Chase’ and the one that is being chased is called ‘Target’.
Correct Answer : To target another spacecraft
Explanation : Chase maneuver is performed for docking operation. This is done in otder to carry out maintenance task, refuel another spacecrafts or deorbiting.
Correct Answer : 3
Explanation : There are three orbital maneuvers carried out in a bi-elliptical orbit. The first maneuver moves spacecraft into an elliptical transfer orbit, second maneuver raises periapsis of first transfer ellipse equal to radius of outer circle. The final maneuver reduces the radius at apogee of the second transfer ellipse to equal the radius of the outer circle.
Explanation : In the bi-elliptic orbit, there are two delta-v burn provided. The first burn is at the apogee of the initial circular orbit whichmakes it enter into first transfer orbit. After this, the second burn is at the perigee of the transfer orbit 1 which makes the object enter the second transfer orbit.
Correct Answer : First transfer orbit
Explanation : In the first maneuver of the bi-elliptic transfer, the object is moves to the first transfer ellipse that has a radius much larger than the radius of the final circular orbit.
Correct Answer : Third burn
Explanation : The third burn is retrograde i.e. the burn is opposite to the direction of the motion. This is done to slow down the object and circularize the orbit by lowering the perigee to the final orbit’s radius.
Explanation : Despite making use of more than one engine burn, bi-elliptic maneuver is more efficient than the Hohmann transfer. It has a greater travel time, but requires less delta-v in total.
Correct Answer : Second transfer orbit
Explanation : In the first maneuver of the bi-elliptic transfer, the object is moves to the second transfer ellipse. This raises the perigee of the first transfer ellipse equal to the radius of the outer circle.
Correct Answer : Energy change
Explanation : There are four types of single impulse maneuver-Adjustment of perigee and apogee height, simple rotation of the line of apsides, simple plane change and combined change of apsis altitude with plane orientation. There is no change in energy involved by applying single impulse.
Correct Answer : 1 km/s
Explanation : The change in velocity for the single impulse maneuver is always higher than 1km/s as there are no re- fueling stations in the space for the spacecraft, so the Δv has to be calculated beforehand to minimize propellant mass carried for the payload.
Correct Answer : True
Explanation : One of the uses of single impulse maneuver is to raise or lower the apogee and perigee radius. This is done by creating an impulse/burn at the perigee or apogee. This burn should occur at a flight path angle of 0 degrees to have the maximum efficiency.
Explanation : For non- intersecting orbits, single-impulse maneuver is not feasible. This is when multi- impulse maneuver is carries out. For coplanar orbits also it is an efficient means.
Correct Answer : One-tangent transfer
Explanation : To transfer a satellite between orbits in less time but with more energy than that is required to complete by the Hohmann transfer, one- tangent burn transfer orbit is used. Transfer orbit is tangential to the initial orbit. It intersects the final orbit at an angle thus, infinite number of transfer orbits are possible.
Correct Answer : Single-impulse maneuver
Explanation : Hohmann, Bi-elliptic and Phasing maneuver involve multiple impulses to achieve the final orbit. Meanwhile single impulse maneuver makes use of one impulse to adjust perigee and apogee height, rotate line of apsides and change plane.
Correct Answer : Half of the transfer ellipse period
Correct Answer : When impulse is applied tangential
Explanation : For a coplanar maneuver, multi-impulse maneuver is very efficient. The minimum velocity impulse is achieved when the impulse is applied in the same direction of initial and final velocity vector. This is known as tangential impulse.
Correct Answer : Hohmann transfer
Explanation : When the initial and final orbits are circular, the optimal maneuver is called a Hohmann transfer. This transfer consists of two tangential velocity impulses which I applied at the initial and final radius.
Correct Answer : Perigee and apogee of the final orbit
Explanation : When there is a Hohmann transfer, the smallest possible transfer ellipse occurs when the transfer takes place at either apogee of perigee of the final orbit which is at a point opposite to the terminating point.
