Revenue - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Services revenue	$ 786	$ 912	$ 1,740	$ 1,778
Grant revenue	1,475	482	2,049	1,553
Total revenue	2,261	1,394	3,789	3,331
Project revenue
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Services revenue	442	635	975	1,451
Engineering services revenue
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Services revenue	$ 344	$ 277	$ 765	$ 327