Robotic missions have landed on Venus, Mars, Saturn's moon Titan, and the asteroid Eros.
For decades, Britain steered clear of human space missions, investing instead in robotic missions and satellites.
Without a human presence in space, support even for robotic missions is likely to dry up.
China has lifted astronauts into orbit and sent its first robotic missions to the moon.
Though robotic missions are easier to achieve, the X Prize competitors still face formidable challenges, not to mention extravagant costs.
They say there are great scientific and commercial benefits of having humans in space as opposed to just robotic missions.
Of the 43 robotic missions to Mars, including fly-bys, attempted by four countries, only 18 have been total successes.
For example, robotic missions are increasingly capable of scientific work in space, and they cost far less than human crews.
Scientific missions continue to benefit from advances in technology, extending the reach and capabilities of robotic missions.
The ESI awards are designed to support NASA exploration goals including robotic missions to Mars and beyond.
The House bill, the writers said, would leave "substantially underfunded" the areas of technology development, commercial spaceflight, robotic missions, and university and student research.
