The thrust \( F \) produced by a rocket can be calculated using the formula:
\[ F = \dot{m} v_{e} \]
where:
- \( F \) is the thrust,
- \( \dot{m} \) is the mass flow rate of the fuel (in kg/s),
- \( v_{e} \) is the exhaust velocity (in m/s).
Given:
- \( \dot{m} = 281 \) kg/s,
- \( v_{e} = 4 \) km/s \( = 4000 \) m/s (since 1 km = 1000 m).
Now we can substitute the values into the thrust equation:
\[ F = 281 , \text{kg/s} \times 4000 , \text{m/s} \]
Calculating this gives:
\[ F = 1124000 , \text{N} \]
To convert Newtons to MegaNewtons (MN):
\[ F = \frac{1124000 , \text{N}}{10^6} = 1.124 , \text{MN} \]
Thus, the thrust of the rocket is:
\[ \boxed{1.124 , \text{MN}} \]