BALANCE SHEET COMPONENTS (Tables)

12 Months Ended

Dec. 31, 2020

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Prepaid Expenses and Other Current Assets

Prepaid expenses and other current assets consisted of the following at December 31, 2020 and 2019, respectively:

	As of December 31,
	2020		2019
Materials and supplies	$	—	$	1,872
Prepaid expenses and other current assets	5,368		2,663
Total prepaid expenses and other current assets	$	5,368	$	4,535

Property, Plant and Equipment

Property and equipment is stated at cost less accumulated depreciation. Repair and maintenance costs are expensed as incurred. Depreciation is recorded on a straight-line basis over each asset's estimated useful life.

Property and Equipment	Useful life
Machinery and equipment	5 - 20 years
Furniture and fixtures	7 years
Leasehold improvements	Shorter of useful life or lease term
Software	3 years
Building	12 years

Property and equipment consist of the following at December 31, 2020 and 2019, respectively:

	As of December 31,
	2020		2019
Machinery and equipment	$	14,820	$	13,483
Furniture and fixtures	1,480		1,228
Leasehold improvements	1,488		1,437
Software	4,285		1,909
Building	—		33,248
Finance lease asset	34,775		—
Construction-in-progress	21,218		4,264
Other	1,750		1,309
Property and equipment, gross	79,816		56,878
Less: accumulated depreciation and amortization	(8,415)		(3,500)
Total property and equipment, net	$	71,401	$	53,378

Schedule of Accounts Payable and Accrued Liabilities

Accrued expenses and other current liabilities consisted of the following at December 31, 2020 and 2019, respectively:

	As of December 31,
	2020		2019
Accrued payroll and payroll related expenses	$	1,105	$	1,385
Accrued stock issuance costs	285		4,695
Accrued outsourced engineering services	2,514		3,205
Accrued purchases of property and equipment	2,533		433
Accrued legal expenses	8,845		243
Other accrued expenses	2,457		804
Current portion of finance lease liability	1,070		—
Current portion of BTS lease financing liability	—		660
Total accrued expenses and other current liabilities	$	18,809	$	11,425