SUBSEQUENT EVENTS (Details)	Nov. 01, 2021 USD ($) day $ / shares shares	Oct. 25, 2021 USD ($)	Jul. 01, 2021 $ / shares
Subsequent Event [Line Items]
Conversion price (in dollars per share) | $ / shares			$ 1,000
Subsequent Event | Senior Notes | Convertible Notes
Subsequent Event [Line Items]
Loan Amount	$ 155,000,000
Debt instrument, stated rate (as a percent)	6.25%
Proceeds from offering	$ 133,900,000
Portion to fund funds payable		$ 33,700,000
Portion to fund engineering services		13,000,000
Portion to fund repayment under credit facility		10,900,000
Portion to fund repayments under certain secured equipment leases		$ 400,000
Issue price, percentage	90.00%
Conversion price (in dollars per share) | $ / shares	$ 5.89
Debt instrument, convertible, percentage of conversion premium (as a percent)	37.50%
Share price (in usd per share) | $ / shares	$ 4.28
Percentage of common stock issuable upon conversion	19.99%
Minimum percentage of common stock issuable upon conversion of the notes	130.00%
Debt Instrument, convertible, threshold trading days | day	20
Debt instrument, convertible, threshold consecutive trading days | day	30
Percentage of offer amount for escrow account to be released	75.00%
Special mandatory redemption date, term	9 months
Satisfaction of reporting conditions, term	6 months
Satisfaction of reporting conditions, additional interest, term	3 months
Debt instrument, conversion ratio	0.1699235
Subsequent Event | Senior Notes | Convertible Notes | Debt Instrument, Redemption, Period One
Subsequent Event [Line Items]
Redemption price, percentage (as a percent)	100.00%
Subsequent Event | Senior Notes | Convertible Notes | Debt Instrument, Redemption, Period Two
Subsequent Event [Line Items]
Redemption price, percentage (as a percent)	100.00%
Subsequent Event | Senior Notes | Convertible Notes | Debt Instrument, Redemption, Period Three
Subsequent Event [Line Items]
Redemption price, percentage (as a percent)	100.00%
Subsequent Event | Unsecured Debt | Convertible Notes
Subsequent Event [Line Items]
Percentage of potential principal amount redeemed	25.00%
Debt instrument, convertible, percentage of additional interest on conversion (as a percent)	1.00%
Subsequent Event | Unsecured Debt | Convertible Notes | Maximum
Subsequent Event [Line Items]
Common stock issued upon conversion of the convertible notes (in shares) | shares	36,214,960
Debt instrument, conversion ratio	0.2336449
Subsequent Event | Unsecured Debt | Convertible Notes | Debt Instrument, Redemption, Period Four
Subsequent Event [Line Items]
Redemption price, percentage (as a percent)	100.00%
Subsequent Event | Unsecured Debt | Convertible Notes | Debt Instrument, Redemption, Period Five
Subsequent Event [Line Items]
Redemption price, percentage (as a percent)	100.00%