Space is Difficult

Why Is It So Difficult to Explore Outer Space?

Space is exciting to study and explore in large part because of how difficult it is to access and how dangerous a place it is once you get there. Space travel is difficult and dangerous for a myriad of reasons, including:

It’s Expensive to Get to Space

It is not cheap to hitch a ride to space! Using a contemporary rocket to send a simple payload into Low Earth Orbit (LEO), which ranges from roughly 400–2,000 km above the Earth’s surface, could cost upwards of $10,000 per pound of payload. Reaching the Moon, which is about 200 times further away from Earth than LEO, is many hundreds of times more expensive. Any spacecraft attempting to reach the Moon needs its own fuel, engines, and all the hardware necessary to control the spacecraft and keep it functioning until it gets to its lunar destination, which adds up to many hundreds of pounds of payload and thus many millions of dollars for a ticket on a rocket. Fortunately, innovations in the space industry such as reusable rocket stages and an increasingly competitive launch vehicle provider landscape are helping to reduce the cost of launching spacecraft.

Say you are ready to buy a ticket for your spacecraft to go to the Moon. That’s great, but that only brings us to the first great hurdle of space exploration: actually leaving Earth.

Rocket Launches are Extremely Violent

The force of a firing rocket engine can subject payloads to vibrations as strong as 12g, or twelve times the acceleration of Earth’s gravity, as they blast into space. Even the sound of rocket engines alone can shake the spacecraft a rocket is carrying into smithereens! For this reason, spacecraft spend a great deal of time going through extensive environmental test campaigns where prototypes are subjected to simulations of the vibrations and acoustics they are expected to withstand during a launch. Designing and testing a spacecraft that can survive a launch takes a great deal of expertise.

Let’s say you’ve proven that your spacecraft can withstand the launch environment. Now you’ve made it into space and can confront the next challenge: the extreme cold (and heat) of space.

Space is Incredibly Cold … and Incredibly Hot

After surviving the violent conditions of launch and separation from their launch vehicle, spacecraft are subjected to immense temperature fluctuations in the vacuum of space. Spacecraft can experience temperatures as high as +125C if exposed to direct sunlight for long periods of time and as low as -200C if they are bathed in Earth’s shadow or experience night on the lunar surface. In order to survive in this environment, spacecraft must be equipped with subsystems that help them tolerate both of these extremes: thermal insulation of vital components to protect against freezing temperatures, and heat pipes and thermal radiators to prevent overheating during extremely hot periods.

But let’s assume you’ve managed to design a thermal system that will keep your spacecraft alive during the hottest and coldest conditions space travel will subject it to. Good job! Now you can cruise through space and deal with the next hazard of space travel: rocks.

Micrometeoroids Can Rip You and Your Spacecraft Apart

Micrometeoroids are tiny rock particles floating through space, typically weighing less than a gram. Although they may sound harmlessly small, they’ve been measured flying through space at speeds well over 10 km/s or 22,500 mph! Their high velocities mean that micrometeoroids can potentially deal significant damage assets in space, puncturing holes in spacecraft and even astronaut space suits.

Micrometeoroids have been an ongoing issue NASA missions, including the ISS and the recently launched James Webb Space Telescope. Protective shielding against these tiny, dangerous space bits has so far prevented any major damage to spacecraft. Even so, micrometeoroids are likely to be as corrosive to spacecraft on long duration space missions as rust is to ships at sea on Earth unless new technologies are developed to protect against the rocky barrage.

Suppose you’ve outfitted your spacecraft with enough shielding to get it to its destination intact. Fantastic! But that still leaves a threat that can’t be seen with the naked eye.

Radiation Could Fry Your Spacecraft’s Computer Brain

Life on Earth thrives thanks to the roughly 60-mile-thick atmosphere surrounding our planet, shielding us from the full brunt of the sun’s radiation by reflecting and absorbing it before it reaches Earth’s surface. Upon leaving the atmosphere, astronauts and spacecraft must be prepared to face the full force of our closest star. Harmful ultraviolet (UV) radiation – highly energized light that is invisible to the human eye – and a steady stream of charged or “ionized” atomic particles known as the “solar wind” can cause cellular damage to unprotected astronauts, eventually resulting in cancer if they are exposed for too long. Even unmanned spacecraft are susceptible to damage by UV radiation and solar wind, since this stream of harmful radiation and particles can damage the sensitive computer components that make robotic missions function. Spacecraft incorporate specialized “Radiation Hardened” electronics and redundant hardware components to minimize the risk that solar radiation will cause a system breakdown before the mission is complete.

But let’s take for granted that you’ve designed a spacecraft that’s well protected from the effects of solar wind and UV radiation. Good work! Now you’re hopefully ready for the journey itself.

There are No Maps (or Rest Stops) in Outer Space

Because of the vast distances that separate even the nearest destinations to Earth in our solar system, space travel requires many precise calculations of spacecraft trajectory and fuel usage. There is currently no way to refuel a spacecraft once it is launched, so any fuel that will be needed for the journey must be carried along from the start, plus plenty of extra fuel just in case. This inability to refuel also means that only the most fuel-efficient courses can be chosen for a mission since they introduce the minimum amount of risk. Compounding the fuel calculations even further is that spacecraft slowly reduce their mass as they expend fuel throughout their journey, making the already difficult math for mission designers even more complex.

Using only the shortest, most efficient paths through space can narrow down potential launch dates for a given mission to only a select number of choices known as “launch windows.” Launch windows vary depending on the destination; launch windows for a lunar mission can be several days long and be several weeks apart, while a mission to Mars might have launch windows several months long separated by multi-year gaps.

Not only is setting a course through space challenging, but determining your exact location along the way is as well. Without the benefit of GPS satellites or physical landmarks to judge distance from, spacecraft have limited ways of knowing where they are on their journey. Special instruments onboard which monitor a spacecraft’s own speed and orientation can be used in conjunction with models of the space environment to accomplish this without human input. NASA’s Deep Space Network (DSN) can also be used to calculate a spacecraft’s distance by measuring the time it takes a transmitted radio signal to reach the spacecraft and be returned to Earth. This method becomes more and more unfeasible the further the mission is intended to travel, with radio signals and commands taking about 2.5 seconds to go to the Moon and back up to 20 minutes to make the roundtrip from Mars.

Let’s imagine you’ve been able to work through all these challenges that come with navigating through space and your spacecraft successfully reaches its destination on the Moon. Congratulations on your momentous achievement! Hopefully you’re also equipped to handle all the hazards that your stay on the Moon has to offer.

Moon Dust Could Your Spacecraft

Because the Moon lacks any atmosphere or liquid water on its surface, lunar soil is much different from what you will find digging in your garden on Earth. Moon dirt is essentially just rocks: big rocks, small rocks, rock fragments (bits broken from big and small rocks), and regolith – a powdery layer of very fine rock dust blanketing the lunar surface like a gritty gray snow. Lunar regolith’s many unique properties – such as its compressibility, minute grain size, and ability to hold static charge – make it both interesting for scientists to study and incredibly hazardous for astronauts and spacecraft to protect themselves against.

If you’ve ever taken a trip to the beach, you’re familiar with sand’s amazing ability to burrow into all your belongings and to hang around forever despite how much cleaning you do. Lunar regolith behaves much the same way, but as the average regolith grain is smaller than a millimeter in size the problem is significantly worse (and without even the benefit of a nice day by the ocean). Regolith nestling its way into the smallest nooks and crannies of a spacecraft will wear down sensitive components like sandpaper. Components designed to move or rotate, like rover wheels or robotic arms, will break down very quickly if their joints aren’t properly protected from this abrasive dust. Astronauts are just as threatened by regolith since its fine particles can quickly clog air filters in pressurized living environments and can cause lung damage and a host of other medical issues if inhaled.

Regolith is bad for human lungs and robotic joints, but it also makes traversing the lunar surface very difficult. Regolith’s fine, powdery texture and compressibility – its ability to be packed down tightly under pressure – make it difficult for astronaut boots and rover wheels to find traction, especially steeper slopes like you might find around a crater. This dusty hazard is even more troublesome when combined with the Moon’s weaker gravity since the lighter downward force makes it all that much more difficult get proper footing. Astrobotic has spent years engineering specialized rover wheels designed to navigate through regolith with ease, traverse up and down steep slopes without slipping, and remaining resistant to wear and tear.

As if that weren’t enough, regolith’s final challenge comes from its propensity to hold static charge and cling to material surfaces. This electrostatic property is more than simply frustrating for astronauts trying to maintain a tidy spacecraft. Regolith buildup on solar panels spells disaster for lunar habitats and robotic equipment reliant on sunlight to function. Solar panels need sun exposure in order to generate electricity, but as regolith dust accumulates on solar cells they become less efficient at converting sunlight into power. This reduced efficiency in turn limits the total amount of electricity available for the spacecraft to use for science experiments and mission critical functions. With enough dust buildup, over time solar panels become unable to generate enough power to even keep essential systems alive, essentially killing the spacecraft if no astronaut comes by to dust off the panels. This is the eventual fate of all robotic spacecraft sent to regolith-rich environments, including Mars. Innovative technologies that can sweep dust off solar panels with a small blast of electricity are a promising way to extend the life of robotic spacecraft, but regolith will continue to prove a challenge for NASA scientists and astronauts to overcome.

But you and your spacecraft have made it this far, so we’ll assume you’ve come prepared to deal with all the dust on the lunar surface, too. Now all that is left is the final predicament: coming home.

Good Luck Coming Home, You’re Going to Need It

Just as there is currently no way to refuel a spacecraft after leaving Earth, there is not yet any infrastructure on the Moon to assist with a return trip. This is where that extra fuel that you (hopefully) stowed in your spacecraft’s fuel tank will come in handy for a manned mission. Fortunately, since gravity on the Moon’s surface is only 1/6 that of Earth it won’t take nearly as much fuel to send your astronauts on their way home.

For unmanned spacecraft where a return to Earth isn’t strictly necessary, mission designers can simply choose for the spacecraft to not come back. Short duration robotic missions designed to operate during a single two-week-long lunar day will simply power down after lunar sunset. Robotic missions intended to operate for months or even years on the Moon will be designed with exceptionally robust thermal systems to protect against the frigid lunar night and come equipped with enough battery supply to keep all systems running until lunar sunrise.

Designing infrastructure that can function on the Moon indefinitely represents the cutting edge of space exploration technology being pursued by companies like Astrobotic. Systems like Astrobotic’s Vertical Solar Array Technology (VSAT) Rover and its wireless charging system are paving the way toward creating a continuous power supply for future lunar assets to tap into. One day these innovations will support a human settlement on the lunar surface where rocket fuel can be manufactured from resources found on the Moon itself, powering exploration even deeper into the solar system where humanity will find ever greater challenges to overcome.