Why is it unlikely that Irene will travel into space?

Irene's unlikelihood to travel into space is primarily linked to her risk of heart failure. In the context of space travel, particularly for missions that require physical endurance and a robust physiological condition, the health of an astronaut is critically assessed. The environment of space poses numerous physical stressors, such as microgravity, which can place significant strain on the cardiovascular system. If an individual has a pre-existing condition like heart failure, it raises serious safety concerns regarding their ability to withstand the rigors of space travel. Such health risks are deemed too hazardous for both the individual and the mission, highlighting why this is the most compelling reason behind her unlikelihood to participate in space journeys.

The other options do not weigh as heavily in the context of astronaut selection criteria. A fear of flying, for instance, could potentially be managed through training, while being allergic to space suits is not a commonly discussed factor in astronaut selection. Similarly, while physical fitness is important, risk factors related to heart health are taken more seriously in assessing overall suitability for space missions. Such critical health concerns play a central role in determining an astronaut's ability to travel to space.