This Wednesday marks a watershed in American spaceflight, as NASA astronauts are set to be launched from U.S. soil for the first time since the space shuttle program ended in 2011. The shuttle was first designed in the 1970s, and though it was tweaked and improved over the years, the basic design remained the same until the program was shuttered.
SpaceX’s Crew Dragon has been in development since 2012, but this week will mark its first crewed test flight. In fact, the two astronauts on board for the test, Bob Behnken and Doug Hurley, were both space shuttle pilots, and Hurley even piloted the final flight of the program in 2011, so they’re well familiar with both craft.
So what has changed in spacecraft engineering in the last few decades? Just how far has technology come, and what are the differences between spacecraft from then and now?
The launch and landing
Both the space shuttle and the Crew Dragon launch in essentially the same way: Being attached to a large rocket booster which fires its engines to propel the craft directly upward and through the atmosphere, before dropping away when no longer needed and leaving the craft in orbit.
In the case of the space shuttle, there was a large external tank in addition to the boosters which held propellant. In the case of the Crew Dragon, it’s attached to a Falcon 9 rocket which is the same type used for various other SpaceX launches.
The big difference between the two is how they land. The space shuttle looked somewhat like an airplane because it was essentially an unpowered glider, which would descend through the atmosphere and gradually glide back down to Earth borne on wind currents. Landing a space shuttle onto a runway was a highly precise, highly challenging endeavor.
The Crew Dragon, however, is much lighter and has a round capsule shape without wings for gliding. Instead, when it is ready to return from orbit, it jettisons all nonessential parts and enters the atmosphere, using drag to slow its speed somewhat. It then releases parachutes which further slow its descent, until it splashes down into the ocean from where the astronauts can be collected.
The fuel: Solid versus liquid
The space shuttle was fueled using solid-propellant rocket boosters which provided the majority of the required thrust to lift the craft into the atmosphere and through Earth’s gravity. Once the propellant was burned up, the boosters would be jettisoned from the craft and fall back into the ocean where they could be collected and reused.
This is similar to how the Crew Dragon’s first stage provides fuel for the launch before falling away and being recovered once the craft is most of the way into orbit.
But there’s one big difference between the two systems: The shuttle boosters used solid fuel in the form of aluminum plus ammonium perchlorate, iron oxide, and some other materials. The Crew Dragon will be launched atop of Falcon 9, which is a liquid-fueled rocket using liquid oxygen and rocket-grade kerosene (RP-1). It’s easier to control the rate of ignition of a liquid fuel than a solid one, as the flow rate can be adjusted more precisely.
In practice, this means that the Crew Dragon will offer a smoother ride than the space shuttle, as one of the NASA astronauts who will be flying aboard the Crew Dragon, Doug Hurley, explained to Digital Trends: “The [space shuttle] solid rocket boosters inherently burn very rough, so the first two minutes you vibrated very significantly. You could shake loose a filling. It was a pretty rough ride.”
By contrast, the Crew Dragon is expected to be less shaky. “The Falcon 9 is a liquid-fueled rocket, so the anticipation is that it will be a much smoother ride.”
The safety of astronauts on board
For all its many achievements, the space shuttle program is also remembered for its deadly accidents. Over its 30-year active period, the shuttle program lost two craft in serious disasters: The Challenger disaster in 1986 and the Columbia disaster in 2003. In both cases, all those aboard were killed, resulting in a total of 14 lives lost.
These disasters occurred either during the launch or landing periods, which are actually the most dangerous — once a craft reaches orbit, it is relatively safe, but getting there and back is the dangerous part.
One reason that these two accidents were fatal is that not only were they using older technology, there were also limited emergency escape options for the crew. There were what are called “black zones” across the launch periods, in which it was impossible for the crew to abort or eject from the spacecraft even if they knew something was going wrong.
Modern spacecraft like the Crew Dragon are therefore designed with an emphasis on systems that allow crew members to eject if there is a problem. They have what is called “end to end abort capability,” meaning the astronauts can be ejected away from the rocket at any point from launch to orbit in case something should go wrong.
SpaceX and NASA have spent a great deal of time testing these systems on the Crew Dragon in what are called escape abort tests, so although the first test flight of a new spacecraft is always risky, the safety systems should be considerably better than those of the space shuttle.
Controlling the vehicle
A major field of development in the last decade has been automation, with spacecraft now able to perform complex functions such as docking with the International Space Station almost entirely autonomously. The Crew Dragon still needs its two astronauts on board to be ready to take over controls in case there are any issues, but if everything goes to plan then the large majority of piloting the craft will be done automatically.
However, should the astronauts need to control the Crew Dragon, the system that they’ll use is very different from the one in the space shuttle.
The space shuttle had thousands of switches, buttons, and screens for inputting and displaying information of all kinds about the vehicle. And while this level of control is important, the sheer volume of inputs could cause issues.
“The shuttle had roughly 2,000 switches and circuit breakers,” astronaut Doug Hurley said. “So there were almost too many in some ways. You really had to be careful actuating a switch because it was very easy to hit the switch next to the one you wanted and to perhaps make things worse rather than better if you were adjusting the vehicle.”
The Crew Dragon uses a touchscreen-based system instead, so there are far fewer buttons and inputs and displays are combined into one. Advances in user interface design have helped to develop a system that has all the options that are required, but it also easier to interact with.
Hurley described the three touchscreen displays between the two pilots as “intuitive,” which, along with the higher level of automation, allow the crew members to focus on their mission rather than on the details of operating the vehicle.
Heralding the future of the industry
One final difference between the two projects has less to do with the vehicles themselves and more to do with the management of the projects: The space shuttle was developed and managed by NASA, while the Crew Dragon is developed and managed by SpaceX with NASA’s oversight and cooperation.
Space exploration is an expensive business, and NASA projects like the next-generation SLS launch system have come under fire for going over budget and costing the public too much. Private companies like SpaceX which already have expertise in areas like reusable rockets may be able to provide launch services for considerably cheaper than if NASA were to develop them itself.
NASA administrator Jim Bridenstine has talked frequently about his desire to make space exploration more affordable for NASA by commercializing low Earth orbit and by the agency becoming a customer of private companies like SpaceX.
However, not everyone is convinced. Some experts have pointed out that the money saved by using private companies may not be that much, considering the delays to projects including SpaceX and Boeing’s contributions to the Commercial Crew programs. And most of these private companies receive considerable government subsidies, so taxpayers end up footing the bill either way.
Others are concerned that private companies will not be as fastidious with multiple layers of redundancy as space agencies are when building their equipment, leaving fewer options for recovery should anything go wrong.
In either case, private space exploration is coming whether it’s wanted or not, and projects like the SpaceX-built Crew Dragon will only become more common in the future through NASA’s Commercial Crew program and others like it.
Watch the launch live
You can watch the historic launch of the Crew Dragon live via NASA TV and see this craft in crewed action for the first time. Check out our post on how to watch the launch for more details.
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