Condensed Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Cash flows from operating activities
Net loss	$ (10,064)	$ (23,199)
Adjustments to reconcile net loss to net cash used in operations:
Depreciation and amortization	726	1,382
Impairment of intangible assets	0	97
Impairment of property and equipment	0	204
Gain on disposal of property and equipment	(450)	0
Share-based compensation expense	839	877
Non-cash interest expense	7	0
Inventory write-downs	168	2,203
Change in:
Accounts receivable, net	1,079	(29)
Costs and estimated earnings in excess of billings on uncompleted contracts	0	987
Inventory	24	(1,335)
Other current and non-current assets	104	2,021
Accounts payable	(340)	(982)
Accrued liabilities	(1,750)	(1,360)
Deferred revenue	(21)	28
Other currrent liabilities	(1,678)	(146)
Operating lease liabilities	(491)	(481)
Net cash used in operating activities	(11,847)	(19,733)
Cash flows from investing activities
Proceeds on sale of property and equipment	525	0
Purchases of property and equipment	(94)	(671)
Net cash provided by (used in) investing activities	431	(671)
Cash flows from financing activities
Principal payments under finance leases	(19)	(15)
Proceeds from long-term debt	1,571	0
Net proceeds from issuance of common stock	9,054	13,295
Net cash provided by financing activities	10,606	13,280
Change in cash and cash equivalents, and restricted cash	(810)	(7,124)
Cash, cash equivalents and restricted cash at beginning of period	6,272	14,201
Cash, cash equivalents and restricted cash at end of period	5,462	7,077
Supplemental schedule of non-cash investing and financing activities
Non-cash additions to property and equipment	19	48
Issuance of common stock for commitment fee	$ 0	$ 258