Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Cash flows from operating activities
Net loss	$ (7,132)	$ (5,949)
Adjustments to reconcile net loss to net cash provided by (used in) operating activities:
Depreciation	419	85
Amortization of intangible assets	29	29
Share-based compensation expense	320	310
Inventory write-downs	4	0
Other non-cash adjustments	(10)	(16)
Change in:
Accounts receivable, net	(2,487)	85
Costs and estimated earnings in excess of billings on uncompleted contracts	422	(256)
Inventory	18	(819)
Other current and non-current assets	(702)	(79)
Accounts payable	(1,010)	(320)
Accrued liabilities	755	315
Billings on uncompleted contracts in excess of related costs	(1)	(106)
Other current liabilities	(39)	(8)
Other long-term liabilities	(142)	0
Net cash used in operating activities	(9,556)	(6,729)
Cash flows from investing activities
Purchases of property and equipment	(182)	(755)
Net cash used in investing activities	(182)	(755)
Change in cash and cash equivalents	(9,738)	(7,484)
Cash, cash equivalents and restricted cash at beginning of period	17,401	15,574
Cash, cash equivalents and restricted cash at end of period	7,663	8,090
Supplemental schedule of non-cash investing and financing activities
Non-cash additions to property and equipment	$ 101	$ 713