Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Cash flows from operating activities
Net loss	$ (15,302)	$ (17,367)
Adjustments to reconcile net loss to net cash used in operations:
Depreciation	1,294	679
Amortization of intangible assets	87	87
Share-based compensation expense	721	1,027
Inventory write-downs	1,139	202
Other non-cash adjustments	99	(47)
Change in:
Accounts receivable, net	(5,029)	5
Costs and estimated earnings in excess of billings on uncompleted contracts	(400)	0
Inventory	55	(3,222)
Other current and non-current assets	(98)	(2,221)
Accounts payable	(1,416)	1,769
Accrued liabilities	(188)	101
Billings in excess of costs and estimated earnings on uncompleted contracts	(4)	1,310
Other currrent liabilities	(115)	9,856
Other long-term liabilities	(305)	(26)
Net cash used in operating activities	(19,462)	(7,847)
Cash flows from investing activities
Purchases of property and equipment	(971)	(2,448)
Net cash used in investing activities	(971)	(2,448)
Cash flows from financing activities
Principal payments under capital leases and long-term debt	(2)	0
Increase in deferred rent	139	0
Net proceeds from issuance of common stock and warrants	16,540	20,459
Net cash provided by financing activities	16,677	20,459
Change in cash and cash equivalents	(3,756)	10,164
Cash, cash equivalents and restricted cash at beginning of period	17,401	15,574
Cash, cash equivalents and restricted cash at end of period	13,645	25,738
Supplemental schedule of non-cash investing and financing activities
Property and equipment acquired under capital leases	42	0
Non-cash additions to property and equipment	$ 149	$ 245