by Douglas Messier
NASA’s planetary defense mission to deflect a small asteroid continues to move toward a February 2022 launch date while holding to its $313.9 million budget, according to a new assessment by the Government Accountability Office (GAO).
The Double Asteroid Redirection Test (DART) will fly to the binary asteroid Didymos and impact the smaller of the two bodies to assess techniques for deflecting dangerous asteroids on collision courses with Earth.
NASA originally planned to fly DART on a rideshare mission with another payload. The agency subsequently selected SpaceX’s Falcon 9 as a dedicated booster for the launch from Vandenberg Air Force Base in California.
“According to officials, having a dedicated launch vehicle allows for a new trajectory that reduces the amount of propellant required,” the GAO assessment said. “As a result, the project no longer relies on the NASA Evolutionary Xenon Thruster-Commercial (NEXT-C) technology demonstration, which has experienced development delays.”
NASA’s Glenn Research Center in Cleveland is managing NEXT-C, an electric propulsion technology demonstration project, under the space agency’s Discovery Program.
NASA’s DART mission is part of the international Asteroid Impact and Deflection Assessment, a collaboration with the European Space Agency (ESA) and the Italian Space Agency (ASI).
ASI is contributing the Light Italian CubeSat for Imaging of Asteroids (LICIACube), which will document DART’s impact of Didymos.
“In November 2019, the European Space Agency (ESA) approved HERA, a possible partner mission due to launch in 2024, which will provide additional follow-up analysis of DART’s impact. NASA and the ESA have not yet reached a formal agreement on this contribution,” the report said.
GAO’s assessment of DART follows.
NASA: Assessments of Major Projects
Report to Congressional Committees
Government Accountability Office
Double Asteroid Redirection Test
The DART project plans to travel to the near-Earth asteroid Didymos, a binary system, and impact the smaller of the two bodies. NASA will assess the deflection result of the impact for possible future use on other potentially hazardous near-Earth objects.
The project stems from the NASA Authorization Act of 2008 and responds to near-Earth object guidance by the Office of Science and Technology Policy to better understand our impact mitigation posture, and to a recommendation by the National Research Council Committee to conduct a test of a kinetic impactor.
The DART mission is part of the Asteroid Impact and Deflection Assessment, which is an international investigation and collaboration with the European Space Agency and the Italian Space Agency.
The DART project continues to operate within its cost and schedule baselines. In April 2019, the Launch Services Program selected the SpaceX Falcon 9 as the dedicated launch vehicle for the DART project, as opposed to a rideshare option.
According to officials, having a dedicated launch vehicle allows for a new trajectory that reduces the amount of propellant required. As a result, the project no longer relies on the NASA Evolutionary Xenon Thruster-Commercial (NEXT-C) technology demonstration, which has experienced development delays.
According to project officials, NASA continues to fund NEXT-C to accompany DART but if delays continue, DART can fly without it. Project officials plan to review the status of NEXT-C between December 2019 and February 2020 to reach a final decision on whether it will fly on DART.
As of October 2019, the project reported that it has a signed agreement with the Italian Space Agency (ASI) for a CubeSat contribution. Similar to NEXT-C, DART will not delay launch to accommodate this contribution if delays materialize because it is not required to achieve mission success.
Cost and Schedule Status
The DART project continues to work within its cost and schedule baselines set in August 2018. In August 2019, the project amended its internal cost and schedule goals, pushing its internal launch readiness date back by 1 month to July 2021, to accommodate the dedicated launch service that was selected, among other changes. The project now has 7 months of schedule reserve remaining to its February 2022 baseline launch date.
The launch service selection was competed, and the Launch Services Program selected a dedicated launch vehicle for DART, the SpaceX Falcon 9, rather than a rideshare option.
According to officials, this allows for a new trajectory that reduces the amount of propellant required removing reliance on NEXT-C, an electric propulsion technology demonstration project managed at Glenn Research Center under the Discovery Program.
The new trajectory no longer includes a flyby of a potentially hazardous asteroid, originally planned to calibrate sensors and tune the subsystem used to autonomously drive the spacecraft to impact the smaller body of the Didymos asteroid system.
Project officials said this carries some risk to navigation system testing but they see the risk as acceptable given available ground simulation and in flight testing using the moons of Jupiter.
Design and Technology
DART held its critical design review in June 2019 with approximately 86 percent of design drawings released, just below the best practice of releasing 90 percent of design drawings at this review. Our product development best practices work has shown that meeting this metric lowers the risk of projects experiencing design changes and manufacturing problems that can lead to cost and schedule growth.
Although DART does not need NEXT-C to meet its requirements, NASA still plans for the separately funded technology demonstration to fly on DART. The project had reported concerns about on-time delivery of NEXT-C due to ongoing developmental issues, and was pursuing two parallel development paths, one expecting delivery of NEXT-C and one expecting to use a mass simulator—an object of similar weight and balance—in place of NEXT-C, to mitigate this risk.
As of December 2019, however, NEXT-C may meet DART’s schedule needs. According to officials, the parallel development approach required additional cost and time compared to pursuing a single development path.
Project officials plan to complete a full review of NEXT-C between December 2019 and February 2020, with the goal of delivering NEXT-C in February 2020 prior to the start of project-level integration and testing.
Project officials told us that in October 2019 NASA decided to descope the electric propulsion gimbal assembly due to cost overruns and other contractor issues. The gimbal was designed to connect NEXT-C to DART to allow adjustments to the direction of propulsion.
Officials said they will not add funds to the gimbal assembly contract to continue work, and now plan to use a stationary mount, which is simpler and should yield cost and schedule savings.
As of October 2019, NASA reported that it has signed an agreement with the Italian Space Agency (ASI) to contribute the Light Italian CubeSat for Imaging of Asteroids (LICIACube) that will document DART’s impact of Didymos.
According to officials, there is some risk that the contribution could be delivered late. To mitigate this risk, project officials purchased a deployment box—a device used to integrate the CubeSat and allow it to launch with DART as a ride-along—identical to the deployment box ASI plans to use.
Officials explained that this purchase provides schedule margin for the satellite’s delivery to DART. This contribution is not required for DART to achieve mission success, however, and officials said they will not delay DART’s launch to accommodate LICIACube.
In November 2019, the European Space Agency (ESA) approved HERA, a possible partner mission due to launch in 2024, which will provide additional follow-up analysis of DART’s impact. NASA and the ESA have not yet reached a formal agreement on this contribution.
Project Office Comments
In commenting on a draft of this assessment, DART project officials stated that as of January 2020, the testing of the flight NEXT-C thruster and electronics has gone very well, and the NEXT-C system is on track for a timely delivery for integration on the spacecraft. Officials also provided technical comments on a draft of this assessment, which were incorporated as appropriate.