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Schedule of Revenue by Major Customers by Reporting Segments (Details) - USD ($)
$ in Thousands
 3 Months Ended 9 Months Ended
Jan. 31, 2022
Jan. 31, 2021
Jan. 31, 2022
Jan. 31, 2021
Product Information [Line Items]        
Revenues $ 484 $ 317 $ 1,003 $ 604
Revenue Benchmark [Member] | Customer Concentration Risk [Member] | Eni S.p.A [Member]        
Product Information [Line Items]        
Revenues 34 14 135
Revenue Benchmark [Member] | Customer Concentration Risk [Member] | Department of Energy [Member]        
Product Information [Line Items]        
Revenues 102 182
Revenue Benchmark [Member] | Customer Concentration Risk [Member] | EGP [Member]        
Product Information [Line Items]        
Revenues 223 163 379
Revenue Benchmark [Member] | Customer Concentration Risk [Member] | ACET [Member]        
Product Information [Line Items]        
Revenues 33 37
Revenue Benchmark [Member] | Customer Concentration Risk [Member] | Valaris FNI [Member]        
Product Information [Line Items]        
Revenues [1] 7 142
Revenue Benchmark [Member] | Customer Concentration Risk [Member] | Brigham Young University [Member]        
Product Information [Line Items]        
Revenues 66 66
Revenue Benchmark [Member] | Customer Concentration Risk [Member] | Nippon Kaiyo [Member]        
Product Information [Line Items]        
Revenues [2] 78 78
Revenue Benchmark [Member] | Customer Concentration Risk [Member] | Naval Surface Warfare Center [Member]        
Product Information [Line Items]        
Revenues [2] 98 98
Revenue Benchmark [Member] | Customer Concentration Risk [Member] | Other [Member]        
Product Information [Line Items]        
Revenues $ 133 $ 27 $ 260 $ 53
[1] 3Dent related consulting
[2] MAR related sales