Supplemental Balance Sheet Disclosures - Unbilled Receivables (Details)	3 Months Ended	6 Months Ended
Mar. 31, 2018 USD ($) customer	Mar. 31, 2017 USD ($)	Mar. 31, 2018 USD ($) customer	Mar. 31, 2017 USD ($)	Sep. 30, 2017 USD ($)
Unbilled Receivables
Unbilled receivables, net of progress payments	$ 926,629		$ 926,629		$ 1,480,822
Number of customer accounted \| customer	1		1
Cumulative change in operating income resulting from changes in estimates	$ (1,143,511)	$ 2,985,918	$ (2,195,072)	$ 1,390,623
Inventory valuation
Raw materials	3,244,976		3,244,976		2,920,209
Work-in-process	733,211		733,211		794,756
Finished goods	462,355		462,355		464,689
Inventories	4,440,542		4,440,542		4,179,654
Prepaid expenses and other current assets
Prepaid insurance	362,873		362,873		402,300
Income tax refund receivable	268,978		268,978		260,509
Other	319,398		319,398		429,255
Total prepaid expenses and other current assets	951,249		951,249		$ 1,092,064
Long-term contracts accounted for under percentage-of-completion
Unbilled Receivables
Cumulative change in operating income resulting from changes in estimates	$ 0	$ (33,000)	$ 0	$ 121,000

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Carrying amount as of the balance sheet date of income taxes previously overpaid to tax authorities (such as U.S. Federal, state and local tax authorities) representing refunds of overpayments or recoveries based on agreed-upon resolutions of disputes. Also called income tax refund receivable.

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Carrying amount, net of valuation reserves and adjustments, as of the balance sheet date of merchandise or goods held by the company that are readily available for sale.

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Amount after valuation and LIFO reserves of inventory expected to be sold, or consumed within one year or operating cycle, if longer.

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Carrying amount, net of valuation reserves and adjustments, as of the balance sheet date of unprocessed items to be consumed in the manufacturing or production process.

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Carrying amount, net of reserves and adjustments, as of the balance sheet date of merchandise or goods which are partially completed. This inventory is generally comprised of raw materials, labor and factory overhead costs, which require further materials, labor and overhead to be converted into finished goods, and which generally require the use of estimates to determine percentage complete and pricing.

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