def compute_impulse_per_motor(total_impulse):
    """Computes impulse per motor (set of 2) required to spin rocket at desired rate.

    `PEP 484`_ type annotations are supported. If attribute, parameter, and
    return types are annotated according to `PEP 484`_, they do not need to be
    included in the docstring:

    Args:
        total_impulse (int, float): Total impulse computed from the compute_total_impulse
        function (N-s).

    Returns:
        float: The impulse of a single motor (from a pair) to spin a launch vehicle
        at a particular spin rate.

    .. _PEP 484:
        https://www.python.org/dev/peps/pep-0484/

    """
    if total_impulse <= 0:
        raise ValueError('Total impulse must be a positive value.')
    return total_impulse/2.0