They say politics stops at the water’s edge — and as former leaders of NASA under Presidents George W. Bush and Barack Obama, we can tell you it definitely stops at the atmosphere’s edge. America’s determination to continue to lead in space is one of our truly bipartisan national priorities, underscored by the sustained and shared commitment across administrations and Congress to deep-space discovery and exploration and the world’s first human landing on Mars. And as the annual appropriations bills wind their way through the House and Senate, leaders of both parties must join together to continue this commitment — and fully fund the innovative new technologies these challenging new missions will require.

First among these is building a new rocket launcher powerful enough to lift the enormous cargo loads needed to support human exploration of Mars or to reach even deeper beyond the red planet into the depths of our solar system and beyond.

NASA’s Space Launch System will feature the highest thrust and largest payload capacity ever developed. The SLS will offer almost two-and-a-half times the payload mass and six times the volume of any existing or planned U.S. launchers. The SLS in its final form will have about 10 percent greater lift capacity than the Saturn V — the only other beyond-Earth-orbit human launcher ever flown.

There are significant reasons why heavy lift is crucial for deep-space human exploration. Future Mars landings, for instance, would require at least the equivalent mass of the International Space Station — which took 10 years and 30 missions to complete — to be launched from Earth. The SLS, with its 130 metric-ton lift capability, could accomplish this in just six or seven flights, making the missions far less complex and more cost-effective.

In contrast, it would take about 30 flights of our current Delta, Atlas or Falcon 9 heavy-launch vehicles to do the same job. More launches necessarily mean more cost and risk.

Only the SLS has enough room to accommodate large, critical payloads such as planetary landers and bulky in-space habitats and other structures. Packaging such systems into a space six times smaller would be extraordinarily challenging and would dramatically increase cost and risk while limiting overall mission capabilities.

The SLS’s higher thrust also means faster transit times to deep-space locations, reducing the cost of mission operations, allowing simpler spacecraft design, and giving mission planners critical flexibility. For example, using the SLS reduces the transit time for the Europa mission by half compared to other launch vehicles. And ultimately, these benefits will accrue not just to space exploration and human spaceflight missions, but to all potential rocket users — including the Department of Defense, and civil and commercial operators.

The SLS vehicle design materialized from an extensive, unbiased set of NASA technical studies that compared all possible scenarios, with a focus on efficiency and budget constraints. Experts inside and outside of NASA were fully integrated into the decision-making process. Among the factors driving the selection of the 130 metric-ton SLS design were human exploration requirements, the state of propulsion technology, the health and capability of the industrial base and the overall budget outlook.

The resulting choice built on propulsion technologies developed and “battle tested” in the space shuttle program, which has an unparalleled flight heritage and demonstrated record of reliability. That will drive down design and development risk and keep long-term costs low. Contrary to some suggestions, the SLS will be very competitive with the advertised price of commercial U.S. systems — on the order of $4.5 million per ton of payload.

NASA’s current policies and its commitment to the SLS represents a pragmatic and cost-effective approach to meeting our deep-space exploration needs. It will allow us to focus on a variety of missions to explore space, advance our knowledge of our solar system, learn more about the history of our own planet, accomplish a truly historical Mars landing and inspire future generations.

At a time when so many issues seem polarized and gridlocked, bipartisan congressional support for NASA’s steady, determined march forward to produce the SLS and cement America’s leadership for another generation shows our nation, and its oft-maligned political system, at its very best.

Douglas Cooke is a former NASA associate administrator for exploration systems. Stephen Cook is a former NASA Ares projects manager. David King is a former NASA Marshall Space Flight Center director.