Since the mid-20th century scholars and engineers have estimated the cost for humans to reach Mars. The estimates for this venture have ranged from as little as $2 billion to hundreds of billions of dollars. As of now, there is a growing consensus among experts that the price tag to get to the Red Planet sits around $500 billion.

What the officials promised to do was dramatically reduce the cost of moving people and machinery to space, to make space flight so easy and inexpensive that no one with the means to support extraterrestrial travel would be able to resist the temptation to do it.

The actual cost of going to the Moon was a fraction of the commonly cited figure. The commonly cited figure is $25.4 billion. Yet the actual cost of the first landing (Apollo 11) did not exceed $500 million. What accounts for this difference? We estimate that the United States spent $20.6 billion preparing to land astronauts on the Moon. The cost of preparation far exceeded the expense of the first surface expedition.

Howard McCurdy and Roger Launius propose a method for assessing the financial burden that space expeditions impose on the national economy.  The method calculates the cost of the program as a proportion of the gross domestic product in the year the expedition is approved.  Excerpted from their forthcoming book on NASA Spaceflight: A History of Innovation by Launius and McCurdy, to be published in late 2017 by Palgrave Macmillan.