Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Cash flows from operating activities
Net loss	$ (17,058)	$ (15,591)
Adjustments to reconcile net loss to net cash used in operations:
Depreciation	1,103	910
Share-based compensation expense	619	539
Inventory write-downs	852	4
Other non-cash adjustments	0	(23)
Change in:
Accounts receivable, net	(2,048)	(2,657)
Costs and estimated earnings in excess of billings on uncompleted contracts	987	680
Inventory	203	32
Other current and non-current assets	336	(293)
Accounts payable	(412)	(1,215)
Accrued liabilities	(608)	283
Deferred revenue	0	5,000
Billings on uncompleted contracts in excess of related costs	101	441
Other currrent liabilities	(112)	(79)
Operating lease liabilities	(321)	0
Other long-term liabilities	0	(284)
Net cash used in operating activities	(16,358)	(12,253)
Cash flows from investing activities
Purchases of property and equipment	(513)	(502)
Net cash used in investing activities	(513)	(502)
Cash flows from financing activities
Principal payments under finance leases	(9)	0
Net proceeds from issuance of common stock	7,728	16,782
Net cash provided by financing activities	7,719	16,782
Change in cash and cash equivalents, and restricted cash	(9,152)	4,027
Cash, cash equivalents and restricted cash at beginning of period	14,201	17,401
Cash, cash equivalents and restricted cash at end of period	5,049	21,428
Supplemental schedule of non-cash investing and financing activities
Non-cash additions to property and equipment	15	386
Issuance of common stock for commitment fee	$ 258	$ 0