Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Cash flows from operating activities
Net loss	$ (8,068)	$ (7,132)
Adjustments to reconcile net loss to net cash used in operations:
Depreciation	552	448
Share-based compensation expense	351	320
Inventory write-downs	0	4
Other non-cash adjustments	0	(10)
Change in:
Accounts receivable, net	202	(2,487)
Costs and estimated earnings in excess of billings on uncompleted contracts	(212)	422
Inventory	47	18
Other current and non-current assets	220	(702)
Accounts payable	(193)	(1,010)
Accrued liabilities	(332)	755
Billings on uncompleted contracts in excess of related costs	5	(1)
Other currrent liabilities	(59)	(39)
Operating lease liabilities	(160)	0
Other long-term liabilities	0	(142)
Net cash used in operating activities	(7,647)	(9,556)
Cash flows from investing activities
Purchases of property and equipment	(313)	(182)
Net cash used in investing activities	(313)	(182)
Cash flows from financing activities
Principal payments under finance leases	(4)	0
Net proceeds from issuance of common stock	1,177	0
Net cash provided by financing activities	1,173	0
Change in cash and cash equivalents, and restricted cash	(6,787)	(9,738)
Cash, cash equivalents and restricted cash at beginning of period	14,201	17,401
Cash, cash equivalents and restricted cash at end of period	7,414	7,663
Supplemental schedule of non-cash investing and financing activities
Non-cash additions to property and equipment	$ 221	$ 101