I'm interested in what the main issues in space exploration today are from a professional's perspective. Similar to how the grand challenge issues of computational astrophysics were summarized here in two bullet points, I would like a summarized view of the grand challenges in space exploration. My hope is that focusing on grand challenges from a professional perspective will keep this from being too opinion based. Wikipedia offers the following description of grand challenges:

Grand challenges are more than ordinary research questions or priorities, they are end results or outcomes that are global in scale; very difficult to accomplish, yet offer hope of being ultimately tractable; demand an extensive number of research projects across many technical and non-technical disciplines and accompanied by well-defined metrics.

Given the above, the subject area should be sufficiently small to keep this question manageable.

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    $\begingroup$ I would nominate for manned spaceflight (if that's a goal at all): find a practical propulsive way to get to Mars (etc.) in 2 weeks instead of 5 months safely (for physical and mental health reasons). For unmanned spaceflight it's also increased speed; getting to, and moving around out the asteroid belt and past Pluto in years rather than multi-decades, and for both manned and unmanned, clever, self regenerating mining robots to go get stuff (fuel, oxygen, raw materials) to build infrastructure. All the other things I can think of are on course - giant space telescope arrays, etc. $\endgroup$
    – uhoh
    Oct 31, 2018 at 15:20
  • $\begingroup$ Astronaut Don Pettit summarizes it nicely; leave your dumbmass on Earth, roughly speaking. $\endgroup$
    – uhoh
    Oct 31, 2018 at 15:25
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    $\begingroup$ A lander on Mercury, the last rocky planet without one. Another lander to one of the five dwarf planets. $\endgroup$
    – Uwe
    Oct 31, 2018 at 15:48
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    $\begingroup$ A lander to Europa, the ice covered moon of Jupiter. $\endgroup$
    – Uwe
    Oct 31, 2018 at 16:23
  • $\begingroup$ Mars sample return $\endgroup$ Sep 4, 2019 at 8:14

5 Answers 5


To give the desired global perspective, I surveyed grand challenges identified by NASA, Roscosmos, and ESA.

1. Human presence in space

All three identified areas of growth in terms of human missions. NASA listed "Expand human presence in space" as their number one theme for space technology grand challenges in 2010. Challenges included economical space access, space health and medicine, telepresence, and space colonization.

Roscosmos space strategy for 2010 and beyond included a new generation manned spacecraft for LEO and moon missions, a manned mission to Mars, and a new generation of manned space station for LEO. Manned space flight was assigned the lion's share of the budget, including a goal of manned lunar missions.

ESA Space 4.0 Strategy included "Exploitation of human-tended infrastructures" in LEO and "Extending human presence to the Moon and Mars" as two of the their three common mission goals.

Some common focus areas: commercialization of space, mitigation of the impact of space on human health, and the creation of self-sustaining human environments.

2. Unmanned deep space missions

Another thing in common with all was a focus on deep space. NASA's grand challenges of a space way station, efficient in-space transportation, high-mass planetary surface access, all access mobility, and surviving extreme space environments all serve as enablers to further unmanned deep space exploration.

Roscosmos initially planned to send probes to a whole host of deep space destinations, but following a launch fiasco, revised plans to focus on unmanned lunar missions, with other deep space missions getting postponed. Missions to Mars and Venus are still eyed for the 2020s and 2030s, however.

ESA's other common mission goal (besides the two mentioned above in section 1) is "Returning samples from the Moon and Mars". Notably, this is a goal of NASA and Roscomos deep space exploration as well.

Some common focus areas: gateway stations, lander resiliency, deep-space telescopes, asteroid exploration, and of course Moon and Mars missions


To wrap this back into overall challenges, what has been identified here is that the top focus will be on reducing cost of launch, supporting long-term human survival in space, and enabling a host of deep space missions to further planetary science, astronomy, and resource utilization.


  • $\begingroup$ what about in-situ manufacturing at least of parts of space craft/supporting infrastructure and more autonomous robotic missions? $\endgroup$
    – J. Doe
    Sep 4, 2019 at 5:11
  • $\begingroup$ @J.Doe Yes, that was one of themes that fell under the broad categories above (specifically number 2, since in-situ manufacturing is often paired with asteroid utilization). It wasn't mentioned at every source so I didn't highlight it specifically. $\endgroup$
    – called2voyage
    Sep 4, 2019 at 13:39

I will say the greatest challenge to space exploration would be a way to overcome the rocket equation.


Basically, everything we put into space from earth is inefficient in that a incredibly vast amount of relative tonnage is wasted to overcome earth gravity. If we could stage launches outside of earth gravity, or even less close to earth's central point of gravity, everything else would be far easier, including Mars, Venus, Jupiter and even targets outside of Sol.

For that reason, you either need a far more efficient propulant, or, as mentioned, stage launches outside of earth gravity well in order to cut the energy requirements. You need to realize that so little mass of a rocket is actually loaded with "useful" science stuff, human personal or gear, its hilarious we actually do launch any rockets at all.

As such, overcoming the rocket equation is the most useful as well as most pressing goal mankind would need to conquer for any other space-exploration related goals.

Without the ability to put more real tonnage onto a space vehicle, everything else is just a distant dream.

Challenges like putting a man onto mars or mining asteroids are, in my opinion, trivial compared to the importance of actually "solving" the rocket equation in a manner that allows efficient travel into actual space.

  • Way more autonomous/context aware robotic space crafts which have more intelligent built-in procedures.
  • Space mining, processing and in-situ manufacturing of at least parts of space crafts, water, fuel and supporting infrastructure.
  • Getting first high res images of exoplanets, for a example with advanced quantum interferometry combined with Earth's or Sun's gravitational lens.

In my opinion, the greatest unexplored frontiers in space exploration is anything related to humans in deep space for a long time, particularly to somewhere like Mars or a long duration Moon voyage. Specifically, the two greatest questions (In my opinion) are:

  1. How does the human body respond long term to gravity less than Earth's?
  2. Is there a directionality to the Solar Energetic Particle radiation? If so, this could allow for more targeted radiation shielding.

I see these as the major developments required for serious long term space exploration and colonisation.

-Developing a space station and vehicle designs with artificial gravity using centrifuges.

-Developing asteroid mining, initially to produce water, oxygen and hydrogen for orbital refueling

-Developing nuclear thermal propulsion and nuclear power reactors for in space and on-planet use.

-Developing orbital construction techniques, using robotics wherever possible.


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