When it comes to space exploration, one of the greatest pain points is the sheer cost of transporting cargo and astronauts into space, which by one estimate is $50 million a pop. Getting into space is the easy part, it’s the cost that holds people back. No wonder Elon Musk’s SpaceX has been working overtime on developing reusable launch vehicles — by reusing rockets, SpaceX can effectively spread out the cost of each launch over several missions.

With that in mind, here are two innovations still in the formative stages that one day could make space exploration easier, cheaper and quite possibly, more accessible to the average person.

The XS-1 space plane

The first innovation is a reusable space plane — the XS-1 — that can be flown to space and back multiple times. According to DARPA, the goal of the XS-1 program is to create a plane that can fly to space at least 10 times in 10 days, at a cost of just $5 million each. DARPA has framed the development of the XS-1 space plane as an innovation challenge, providing just a few basic requirements of what such a space plane must be able to do. In addition to being able to make 10 trips in 10 days, the space plane must have the ability to fly at Mach 10 and have the same size and weight as a corporate jet.

On so many levels, the idea of a space plane makes sense — it has the appeal of being a reusable launch vehicle, plus it builds on the technology platform that already exists with NASA’s space shuttle program and the Air Force’s super-secretive X-37B, an unmanned space plane that can stay in space for months at a time. If the XS-1 program ever gets off the ground, it would become the technological heir apparent to the space shuttle program, which finally came to a close in July 2011.

DARPA has announced that three groups of aerospace innovators would receive $6.5 million in funding each (nearly $20 million overall) to proceed with Stage 2 research on their space plane concepts. One is a consortium of Boeing and Blue Origin (Jeff Bezos’s company). Another is a consortium of Northrop Grumman, Virgin Galactic (Richard Branson’s company) and Scaled Composites (Burt Rutan’s company). The third recipient is Masten Space Systems. Based on the initial design concepts, the three front-runners look much like technologically updated space shuttles, only augmented with hypersonic propulsion systems.

The ThothX space elevator

The second concept for making space exploration easier and cheaper is a space elevator. This is one of those science fiction concepts that has existed for more than a century, famously appearing in Arthur C. Clarke’s 1978 novel “The Fountains of Paradise.” In the classic conception of the space elevator, a super-thin tower or cable would extend more than 22,000 miles into geostationary orbit in outer space, and cargo supplies would be ferried up and down this tower.

The space elevator concept obviously eliminates the need for expensive rockets, but it does require quite a bit of engineering acumen and the type of materials that don’t currently exist today to support such a structure. Multiple attempts have been made at developing a space elevator (including one by LiftPort to build a space elevator for the moon), but the key sticking point appears to be finding the right type of carbon-based nanomaterial that would enable the tower to support itself.

A team of Canadian innovators at Thoth Technology, though, has come up with a twist on the concept that can best be thought of as an inflatable, freestanding space elevator. According to a patent that was granted by the U.S. Patent and Trademark Office in July, the so-called ThothX Tower would extend around 12.4 miles into the stratosphere rather than into outer space. (By way of comparison, that’s still about 20 times taller than the Burj Khalifa in Dubai.) Spaceships would take off and land on a landing strip on top of the tower, while astronauts and cargo would be ferried up to the stratosphere by means of a pneumatic tube, an electrical elevator, or a funicular-like railway that would climb to the top.

Such a space elevator might cut the cost of space flight by as much as 30 percent, mostly as a result of reduced fuel costs to ferry heavy payloads into space. And the plan might lead to further cost advantages if it leads to new space tourism ventures. Spaceships would simply await on top of the tower for refueling and their next flights into space, while potential tourists would take some sort of express elevator to the top. The U.S. patent application also mentions that the space elevator tower might be used for scientific research and communication, potentially opening the door to other commercialization opportunities.

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Both of these space exploration concepts — especially the space elevator — are admittedly moonshot-type innovations and probably won’t happen anytime soon. It’s one thing to have a patent for an innovation, and quite another to transform it into something workable. In the case of the space elevator concept, building the tower into the stratosphere would just be the first step. You’d also need spaceships capable of landing on a thin landing strip 12.4 miles up in the sky. Think of it as parking on top of an incredibly high skyscraper. As we’ve seen with SpaceX’s failed attempts with soft-landing reusable rockets at sea, that’s actually a pretty tall order — especially since any structure in the stratosphere would also need to compensate for high wind speeds.

Of course, the need for an alternative to rocket-powered space flight might be avoided entirely if someone invents a powerful rocket operating on a cheap enough fuel source. However, the reusable space plane and the space elevator serve to illustrate two ingenious approaches to solving a well-known problem: how to get to space easily and cheaply without the need for expensive rockets. If we’re going back to the moon and the Mars and opening up a new age of manned space exploration, we’re going to need as many innovative ideas as we can get.

CORRECTION: An earlier version of this article incorrectly noted that Masten Space Systems was a member of a consortium with XCOR Aerospace. XCOR was one of many suppliers and subcontractors, but their work in support of the contract has already been completed.