Spaceflight Mechanics - Ballistic Missiles Trajectories Quiz(MCQ)

1 .

Which of these trajectories is followed by the ballistic missile?

A)

Ballistic trajectory

B)

Orbital trajectory

C)

Planetary trajectory

D)

Aft-crossing trajectory

Correct Answer : Ballistic trajectory

Explanation : A ballistic missile trajectory is used by missiles for warfare purposes. It is different from the orbit followed by the satellite as the ballistic missile trajectory intersects the Earth’s surface. The trajectory comprises of three portions-powered flight regime, free flight regime and the re-entry regime.

2 .

In which aspect does the trajectory of missile differ from the satellite's orbit?

A)

It follows a parabolic path

B)

It has a brief time of period

C)

It intersects the earth�s surface

D)

It stays within the earth�s atmosphere

Correct Answer : It intersects the earth�s surface

Explanation : The trajectory of a missile differs from a satellite orbit in only one respect-it intersects the surface of the Earth at two places. If we consider only the free-flight portion of the ballistic missile trajectory, then it follows the conic orbit just like a satellite.

3 .

Which of these portions is not a part of ballistic trajectory?

A)

Re-entry portion

B)

Cruise portion

C)

Free flight portion

D)

Powered flight portion

Correct Answer : Cruise portion

Explanation : The ballistic trajectory is composed of three components-powered flight portion which is comprises of path from launch to the burnout, free-flight portion which constituted most of the trajectory and the re-entry portion which lasts until the impact.

4 .

What is the value of the non-dimensional parameter (Q) for a satellite that has escape speed and is on a parabolic orbit?

A)

0

B)

1

C)

2

D)

3

Correct Answer : 2

Explanation : The value of non-dimensional parameter varies from point to point in an orbit. The value of the parameter for a satellite that has an escape speed and is on the path of the parabolic path is 2. Q=1 is the condition for circular orbit.

5 .

What is the trajectory called which corresponds to the higher value of flight-path angle?

A)

Low trajectory

B)

High trajectory

C)

Medium trajectory

D)

Controlled trajectory

Correct Answer : High trajectory

6 .

What is the trajectory called which corresponds to the lower value of flight-path angle?

A)

Low trajectory

B)

High trajectory

C)

Medium trajectory

D)

Controlled trajectory

Correct Answer : Low trajectory

Explanation : Flight path for a trajectory yields two solutions. The solution having the smaller value is known as the low trajectory and the solution with higher value is known as the high trajectory. The nature of high or low trajectory is dependent on the value of Qbo.

7 .

Which of these assumptions is used to find the ballistic missile trajectory equations?

A)

Free flight trajectory is asymmetrical

B)

Oblations of the earth is ignored

C)

The speed of missile stays constant

D)

Rotation of the earth is ignored

Correct Answer : Rotation of the earth is ignored

Explanation : In order to derive the ballistic missile trajectory equations, there are two assumptions made. First is that the rotation of the earth is ignored and second is that the free-flight trajectory is assumed to be symmetrical.

8 .

Which of these conic orbits is followed by the free flight trajectory?

A)

Elliptical

B)

Circular

C)

Parabolic

D)

Hyperbolic

Correct Answer : Elliptical

Explanation : Ballistic missile trajectory is composed of three regimes-powered flight, free-flight and re-entry portion. Free-flight portion is the only part of the trajectory that follows a conic orbit. It constitutes most of the trajectory path. During free-flight the trajectory is part of a conic orbit-almost always an ellipse which is symmetrical.

9 .

If the ratio of current speed to the local circular speed is 1.58 then which of the orbits is followed by the missile?

A)

Circular

B)

Elliptical

C)

Hyperbolic

D)

Parabolic

Correct Answer : Hyperbolic

10 .

Which of these forms the flight-path angle?

A)

Angle between the normal and the tangent

B)

Angle between the local horizontal and the normal

C)

Angle between the velocity at burn-out vector and focal vector

D)

Angle between the local horizontal and the tangent

Correct Answer : Angle between the local horizontal and the tangent

11 .

At maximum range, how many paths are available to reach the target?

A)

0

B)

1

C)

2

D)

3

Correct Answer : 1

Explanation : On plotting free flight range vs flight path angle graph, we get a curve as shown in the figure. The flight path angle first increases then decreases within the range of 0-90 degrees. On reaching the maximum point, there’ only one corresponding flight path angle. For rest of the range values, there are two corresponding flight path angles. Thus, there’s is only one path to the target.

12 .

What is the maximum range angle attained by the missile for the non-dimensional parameter at burn out of 0.79?

A)

40.76 degrees

B)

45.14 degrees

C)

81.52 degrees

D)

90.52 degrees

Correct Answer : 81.52 degrees

13 .

In how many categories are the launching errors classified into?

A)

1

B)

2

C)

3

D)

4

Correct Answer : 2

Explanation : There’s error produced when there’s variation in the speed, launch direction, position of the ballistic missile. They are classified into two errors-down-range errors, out-of-plane errors.

14 .

Which of these errors cause missile to deviate from the target in a different plane?

A)

Incorrect Speed at Burnout

B)

Effect of Down-Range Displacement of the Burnout Point

C)

Effect of a Lateral Displacement of the Burnout Point

D)

None of the above

Correct Answer : Effect of a Lateral Displacement of the Burnout Point

Explanation : Only the effect of lateral displacement at the burnout among the options results in the missile to hit to right or left of the target i.e., it is a out-of-plane error. Rest of them are down-rage errors and the error in the intended plane causes either a long or a short hit.

15 .

If the error in down-range position at thrust cutoff is 5nm, then what will be the error at the impact?

A)

5 nm

B)

10 nm

C)

20 nm

D)

30 nm

Correct Answer : 5 nm

Explanation : An error in down-range position at thrust cutoff produces an equal error at impact. If the actual burnout point is 5 nm farther down-range than was intended, the missile will overshoot the target by exactly 5 nm.

16 .

If the burnout occurs at a higher height than intended, then where does the missile fall?

A)

Missile overshoots the target

B)

Missile falls short of the target

C)

Missile falls to the right of the target

D)

Missile falls at the exact point of the target

Correct Answer : Missile overshoots the target

Explanation : If the burnout occurs higher than intended, the missile overshoots and if burnout occurs too low, the missile falls short of the target in every case.

17 .

If the missile's burnout peed is slow, what happens to the magnitude of error while It lands on the target?

A)

Missile overshoots the target

B)

Missile falls at the left of the target

C)

Missile falls to the right of the target

D)

Missile falls short of the target

Correct Answer : Missile falls short of the target

Explanation : Speed at burnout affects range as causing down-range error. If the missile is too fast at the burnout, it overshoots and if it is too slow, the missile falls short.

18 .

What is the surface velocity at the equator due to Earth's rotation?

A)

1000 ft/s

B)

1524 ft/s

C)

2834 ft/s

D)

3102 ft/s

Correct Answer : 1524 ft/s

Explanation : The Earth rotates once on its axis in 23 hours 56 min producing a surface velocity at the equator of 1524 ft/sec. The rotation is from west to east.

19 .

How is the initial velocity of the ballistic missile compensated?

A)

Adding the initial eastward velocity of launch site

B)

Adding the initial westward velocity of launch site

C)

Subtracting the initial eastward velocity of launch site

D)

Subtracting the initial westward velocity of launch site

Correct Answer : Subtracting the initial eastward velocity of launch site

Explanation : The compensation for the initial velocity is done by recognizing that the true velocity of the missile at burnout is the velocity relative to the launch site (which could be measured by radar) plus the initial eastward velocity of the launch site due to earth rotation.