SAN FRANCISCO — When NASA’s Space Launch System takes off on its maiden voyage, instead of carrying astronauts, the heavy-lift rocket is expected to send 11 cubesats on missions to the Moon, an asteroid and other destinations.
Although the project is still in planning stages, the NASA Human Exploration and Operations Directorate’s Advanced Exploration Systems program has already selected three missions to ride along:
- BioSentinel, a NASA Ames Research Center project to study the damage radiation causes to living organisms.
- Lunar Flashlight, a NASA Jet Propulsion Laboratory cubesat equipped with a solar sail to provide propulsion and illuminate permanently shadowed craters near the Moon’s south pole.
- Near Earth Asteroid Scout, a Marshall Space Flight Center mission to rendezvous with an asteroid and gather detailed imagery.
Officials within NASA’s Science and Space Technology mission directorates are drafting plans to select additional cubesats for the voyage. In June, the Space Technology Mission Directorate’s Centennial Challenges program issued a request for information seeking public input on contests to award $3 million in prizes to competitors who demonstrate advanced cubesat propulsion, communications and longevity in lunar orbit and $1.5 million for cubesats capable of communicating with Earth from 10 times the distance between Earth and the Moon.
All the projects are focused on sending six-unit cubesats, which measure 10 centimeters by 20 centimeters by 30 centimeters, into heliocentric orbit from the second stage of SLS. The cubesats would be released after the rocket sends the Orion capsule into a distant lunar retrograde orbit. The Centennial Challenges solicitation requests comments on how doubling the size of proposed cubesats would benefit various projects.
Under current plans, SLS — which is slated to make its debut at the end of 2017 — would carry a ring of 11 cubesats directly below the Orion crew capsule in the space usually reserved for life-support systems and associated electronics. “SLS will get out of Earth’s gravity well and eject the cubesats in cislunar space where you could use low energy propulsion such as solar sails or ion engines to go to different places and do different things,” said Barbara Cohen, Lunar Flashlight science lead at NASA’s Marshall Space Flight Center in Huntsville, Alabama.
As NASA’s Space Technology Mission Directorate examines comments submitted in July on proposed prizes, NASA Advanced Exploration Systems officials are preparing to review mission concepts for BioSentinel, Lunar Flashlight and Near Earth Asteroid Scout. If those missions are approved, researchers plan to begin designing and building the cubesats.
BioSentinel is designed to extend beyond low Earth orbit the biological research NASA Ames scientists have performed for many years. Future manned missions to an asteroid or Mars will require a better understanding of the radiation environment beyond low Earth orbit, said Matt Sorgenfrei, NASA Ames BioSentinel propulsion system lead.
The BioSentinel mission will carry into a deep-space heliocentric orbit multiple cultures of a genetically modified strain of yeast that researchers have manipulated to respond to DNA damage by reproducing, as well as a radiation spectrometer and dosimeter for taking measurements, Sorgenfrei said.
“We can track the growth of this culture of yeast cells to deduce information about the radiation flux being experienced by the spacecraft in this deep-space orbit,” Sorgenfrei said. “What makes the biology payload exciting is that by studying growth of the yeast cells and their response to DNA damage, we start to build up a little bit of an analogy of what might happen to humans while they are traveling to an asteroid or Mars.”
The BioSentinel team plans to build three identical payloads. In addition to the SLS cubesat, one is for the international space station and the other would remain on the ground. “We would be able over the life of the mission to collect three data points: one from the deep-space environment where you don’t have the benefit of the protection of Earth’s magnetic field, one from the standard low Earth orbit environment where humans have spent the vast majority of their time in space, and this additional control on the ground, which we could blast with specific types of radiation at someplace like Brookhaven [National] Laboratory or let it grow as a standard control.”
Lunar Flashlight is focused on the Moon. The mission is designed to travel to the Moon’s south pole to determine whether it holds water ice that future exploration missions could tap for a variety of uses including fuel production and astronaut hydration.
“We have data from the Lunar Reconnaissance Orbiter and other missions that indicate stores of water trapped at the lunar poles,” Cohen said. “This is a mission to further characterize the surface layer and to understand whether the water ice may exist as a frost on the surface or whether it’s buried at depth.”
In addition, Lunar Flashlight seeks to demonstrate new technology, including an 80-square-meter solar sail to propel and guide the spacecraft into a highly elliptical orbit that passes near the Moon’s south pole. During the majority of the orbit when the cubesat travels far from the lunar surface, the solar sail would provide propulsion and guidance. When the cubesat approaches the Moon, it turns the solar sail to face the sun, making sunlight bounce onto the lunar surface and providing enough light to enable a spectrometer to look for water ice, Cohen said.
The Near Earth Asteroid Scout is designed to use an identical solar sail to enable a cubesat to travel slowly past an asteroid. The cubesat would use an onboard camera with color filters to gather high-resolution imagery.
“The mission paves the way for future exploration of near-Earth asteroids by reducing uncertainty and retiring risk,” said Julie Castillo-Rogez, Near Earth Asteroid Scout principal investigator at JPL.
“We will obtain for the first time up-close observations of a near-Earth asteroid smaller than 100 meter [diameter] and determine what it looks like, its shape, how quickly it rotates and whether there is debris around that object,” Castillo-Rogez said. “High-resolution imaging of the surface will show us the surface regolith and if slopes are stable or there are landslides. This is the type of information we need in preparation for human exploration.”
The three cubesats would use NASA’s Deep Space Network to relay observations. “Because the Orion Multi-Purpose Crew Vehicle will be on its way to circumnavigate the Moon and come home, these huge antennas will be pointing out to deep space. Cubesats floating around in that beam width, we can opportunistically phone home,” Sorgenfrei said.