article_snippet: Option 2 - Least technological risk .
article_snippet: Option 3 - Nasa's current favoured path .
article_snippet: One particular issue is radiation.
article_snippet: You have to be able to create complicated and sophisticated means of avoiding these hazards.
article_snippet: It makes the flight time much shorter and the mass budget is lower.
article_snippet: But the mass budget turns out basically that’s not really the case.
article_snippet: At the end of the day, if you do the calculations properly, you find out that traditional measures like chemical and electrical turn out to be more efficient,’ he said.