Now may be a propitious time to raise the question: Is it better to undertake an occasional manned mission, at a cost of many billions of dollars, to explore asteroids, return to the Moon and journey to Mars, or should we stay close to the planet and exploit a region that so far has been only touched upon, despite the availability of the hugely expensive but sparsely manned international space station? 

There are two dominant scenarios, characterized as follows, admittedly with variations in each.

The first features occasional high-dollar ventures by astronauts to destinations such as asteroids, Mars and the Moon. For the most part, these are long, dangerous journeys, unlikely to sustain public interest for long — until the destination is reached and there is a short spurt of heart-stopping activity. (Missions to Mars generate wide interest only after the spacecraft has landed.) Then comes the long journey home. This scenario calls for infrequent launches on NASA’s Space Launch System, which will therefore be very high cost and result in exploring space at a snail’s pace. The United States is arguably the leader in undertaking such missions, having already sent astronauts to the Moon several decades ago. But it is also the leader in robotic missions, even to the distant planets. A four-decade hiatus has followed the last exploratory manned mission: Apollo. Would another such hiatus follow a manned mission to Mars?

The second scenario envisions robust activity along several lines in low Earth orbit, quite within existing capability and for which the pattern has already been set by the Soviet Union’s Mir and the United States’ Skylab, the follow-on to Apollo. Instead of monster structures like the international space station, there would be turnkey stations mirroring Skylab, of a size that could be lifted into orbit by single flights of the SLS — around 75 metric tons.

It is a fair assumption that many nations in the world would like independent access to a turnkey station, through lease or actual purchase, as well as transportation to and from. A part of it may simply be prestige, but more likely it would be independent research by these nations’ own scientists who need the space environment to proceed. These activities might range from medical research to fundamental materials research and development, particularly in the nano region, a relatively new frontier. 

A second application that caters to frivolous but adventurous tastes is tourist hotels. For some — and there are many who can afford it — a week in Earth orbit would be the adventure of a lifetime.

The new paradigm envisions bustling near-Earth activity, with perhaps hundreds of people in orbit doing valuable work in multiple stations, and at the same time proceeding with robotic exploration of the outer regions, which is being done now with spectacular success. 

It foretells major new industries — design and construction of work stations; design, development and implementation of a reusable transportation system for economical transfer of personnel, and a system for control, monitoring and servicing of stations as they age in service. 

It brings into focus the challenge of operating in low Earth orbit with positive return on investment, as we do at geosynchronous orbit.

This is the only plausible scenario that will ensure a requirement for SLS flights at a reasonable rate. For other proposed missions, flights will be few and far between — possibly years apart. Thus they will be very expensive if one factors in the cost of keeping a launch crew and production in place.

The United States is not the only nation that can undertake this unique opportunity. Russia certainly can do it, and one wonders to what purpose it would be undertaking development of a heavy-lift launch vehicle, as recently announced. China too, a recent newcomer with no presence at the international space station, already has a demonstrated ability with its own station and is capable of huge surprises.

In summary, this is one way to keep a vibrant space program in place, with inherent drivers to develop a reusable passenger transportation system, a vastly improved situation for beneficial discoveries, improved cooperation among nations and an enormous new employment base for technological talent that presently lies dormant, risking loss of skills in an extremely valuable area.

Mars and asteroids can wait. If we take the route of missions spaced decades apart, of which there may be just one, there will exist little reason for the next generation to look to space as a career opportunity.

Edward Hujsak is a career rocket engineer and author of the book “The Future of U.S. Rocketry.”