<?xml version="1.0" encoding="UTF-8"?>

<!--XBRL Document Created with the Workiva Platform-->
<!--Copyright 2024 Workiva-->
<!--r:8864d726-f81c-41f9-a3c8-ffb428e05070,g:d673dff3-7dd9-445f-baa9-0aaa66fce7ed-->
<link:linkbase xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd">
  <link:roleRef roleURI="http://www.ngsgi.com/role/CONDENSEDCONSOLIDATEDBALANCESHEETS" xlink:type="simple" xlink:href="ngs-20240331.xsd#CONDENSEDCONSOLIDATEDBALANCESHEETS"/>
  <link:calculationLink xlink:role="http://www.ngsgi.com/role/CONDENSEDCONSOLIDATEDBALANCESHEETS" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesAndStockholdersEquity_09039bcc-779e-41de-b50e-4de81603f9ac" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LiabilitiesAndStockholdersEquity"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Liabilities_7e887384-2224-458c-8770-f0b6033c3062" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_Liabilities"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquity_09039bcc-779e-41de-b50e-4de81603f9ac" xlink:to="loc_us-gaap_Liabilities_7e887384-2224-458c-8770-f0b6033c3062" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommitmentsAndContingencies_57209bec-94df-49f2-88f8-12f1b3932df4" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommitmentsAndContingencies"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquity_09039bcc-779e-41de-b50e-4de81603f9ac" xlink:to="loc_us-gaap_CommitmentsAndContingencies_57209bec-94df-49f2-88f8-12f1b3932df4" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_b540e5ab-ecfb-437b-8027-9403160ff14e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockholdersEquity"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquity_09039bcc-779e-41de-b50e-4de81603f9ac" xlink:to="loc_us-gaap_StockholdersEquity_b540e5ab-ecfb-437b-8027-9403160ff14e" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesCurrent_39e77e1b-17d9-4823-ab62-4bebfc9500fa" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LiabilitiesCurrent"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsPayableCurrent_5eb239e6-09bb-4bb6-a5fe-6fbe44053ad1" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccountsPayableCurrent"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LiabilitiesCurrent_39e77e1b-17d9-4823-ab62-4bebfc9500fa" xlink:to="loc_us-gaap_AccountsPayableCurrent_5eb239e6-09bb-4bb6-a5fe-6fbe44053ad1" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccruedLiabilitiesCurrent_1f41af01-0c2c-4604-b81b-a7118a66b9a1" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccruedLiabilitiesCurrent"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_LiabilitiesCurrent_39e77e1b-17d9-4823-ab62-4bebfc9500fa" xlink:to="loc_us-gaap_AccruedLiabilitiesCurrent_1f41af01-0c2c-4604-b81b-a7118a66b9a1" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsCurrent_dea04d7a-ea63-4412-998b-1f9ca81bc4b5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AssetsCurrent"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_2ad50dd2-99cc-47f0-9dac-e4f0d36eedae" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_AssetsCurrent_dea04d7a-ea63-4412-998b-1f9ca81bc4b5" xlink:to="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_2ad50dd2-99cc-47f0-9dac-e4f0d36eedae" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsReceivableNetCurrent_41d867b9-1435-41e1-8ba5-b5183fe6ea4b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccountsReceivableNetCurrent"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_AssetsCurrent_dea04d7a-ea63-4412-998b-1f9ca81bc4b5" xlink:to="loc_us-gaap_AccountsReceivableNetCurrent_41d867b9-1435-41e1-8ba5-b5183fe6ea4b" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InventoryNet_63cd8f15-1b2c-4251-94ee-7e356391bfaa" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InventoryNet"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_AssetsCurrent_dea04d7a-ea63-4412-998b-1f9ca81bc4b5" xlink:to="loc_us-gaap_InventoryNet_63cd8f15-1b2c-4251-94ee-7e356391bfaa" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxesReceivable_c8c286fa-5d79-471b-a260-61df462b3f37" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeTaxesReceivable"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_AssetsCurrent_dea04d7a-ea63-4412-998b-1f9ca81bc4b5" xlink:to="loc_us-gaap_IncomeTaxesReceivable_c8c286fa-5d79-471b-a260-61df462b3f37" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PrepaidExpenseAndOtherAssetsCurrent_1dc559b6-ad71-4b48-a58e-1ce9b5043073" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PrepaidExpenseAndOtherAssetsCurrent"/>
    <link:calculationArc order="5" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_AssetsCurrent_dea04d7a-ea63-4412-998b-1f9ca81bc4b5" xlink:to="loc_us-gaap_PrepaidExpenseAndOtherAssetsCurrent_1dc559b6-ad71-4b48-a58e-1ce9b5043073" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Assets_3032cea7-15f5-4f10-85f5-b3d3c2d6b65a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_Assets"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsCurrent_cbe9cde3-6a4b-4275-b050-267e2ab12c70" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AssetsCurrent"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_Assets_3032cea7-15f5-4f10-85f5-b3d3c2d6b65a" xlink:to="loc_us-gaap_AssetsCurrent_cbe9cde3-6a4b-4275-b050-267e2ab12c70" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_ngs_RentalEquipmentNet_c728ad08-c785-4211-b975-cfda273dad12" xlink:href="ngs-20240331.xsd#ngs_RentalEquipmentNet"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_Assets_3032cea7-15f5-4f10-85f5-b3d3c2d6b65a" xlink:to="loc_ngs_RentalEquipmentNet_c728ad08-c785-4211-b975-cfda273dad12" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentOtherNet_d9b78b8c-8021-43d8-a1ed-5a644f7161a8" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PropertyPlantAndEquipmentOtherNet"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_Assets_3032cea7-15f5-4f10-85f5-b3d3c2d6b65a" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentOtherNet_d9b78b8c-8021-43d8-a1ed-5a644f7161a8" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IntangibleAssetsNetExcludingGoodwill_6276347a-a5a6-45c9-ab7e-cda538dd2122" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IntangibleAssetsNetExcludingGoodwill"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_Assets_3032cea7-15f5-4f10-85f5-b3d3c2d6b65a" xlink:to="loc_us-gaap_IntangibleAssetsNetExcludingGoodwill_6276347a-a5a6-45c9-ab7e-cda538dd2122" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssetsNoncurrent_56158a14-d908-4069-83d6-fd744055de95" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherAssetsNoncurrent"/>
    <link:calculationArc order="5" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_Assets_3032cea7-15f5-4f10-85f5-b3d3c2d6b65a" xlink:to="loc_us-gaap_OtherAssetsNoncurrent_56158a14-d908-4069-83d6-fd744055de95" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InventoryNoncurrent_9ca73293-5f5a-4141-ad6f-288cbfde0dac" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InventoryNoncurrent"/>
    <link:calculationArc order="6" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_Assets_3032cea7-15f5-4f10-85f5-b3d3c2d6b65a" xlink:to="loc_us-gaap_InventoryNoncurrent_9ca73293-5f5a-4141-ad6f-288cbfde0dac" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_454e9d37-251b-4fec-b8e4-7208516cd0dc" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockholdersEquity"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockValue_f21797b8-8f81-4cf9-a91f-9454aa959d8b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PreferredStockValue"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_StockholdersEquity_454e9d37-251b-4fec-b8e4-7208516cd0dc" xlink:to="loc_us-gaap_PreferredStockValue_f21797b8-8f81-4cf9-a91f-9454aa959d8b" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockValue_facaec6d-0dcc-429c-857c-942c6bf31d7e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonStockValue"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_StockholdersEquity_454e9d37-251b-4fec-b8e4-7208516cd0dc" xlink:to="loc_us-gaap_CommonStockValue_facaec6d-0dcc-429c-857c-942c6bf31d7e" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapitalCommonStock_2dda56c0-d538-4458-a222-9a573cd6afb2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AdditionalPaidInCapitalCommonStock"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_StockholdersEquity_454e9d37-251b-4fec-b8e4-7208516cd0dc" xlink:to="loc_us-gaap_AdditionalPaidInCapitalCommonStock_2dda56c0-d538-4458-a222-9a573cd6afb2" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsAccumulatedDeficit_368b8210-1d2c-4dfe-b368-68cb0db813a8" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RetainedEarningsAccumulatedDeficit"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_StockholdersEquity_454e9d37-251b-4fec-b8e4-7208516cd0dc" xlink:to="loc_us-gaap_RetainedEarningsAccumulatedDeficit_368b8210-1d2c-4dfe-b368-68cb0db813a8" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockCommonValue_85d1b09b-4596-4d5d-8748-77e5951dd44a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TreasuryStockCommonValue"/>
    <link:calculationArc order="5" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_StockholdersEquity_454e9d37-251b-4fec-b8e4-7208516cd0dc" xlink:to="loc_us-gaap_TreasuryStockCommonValue_85d1b09b-4596-4d5d-8748-77e5951dd44a" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Liabilities_c314bb52-8009-4a60-a748-5e7768dbf02d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_Liabilities"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredIncomeTaxLiabilitiesNet_312bb08b-3f8e-457f-b631-894312f4a23b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DeferredIncomeTaxLiabilitiesNet"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_Liabilities_c314bb52-8009-4a60-a748-5e7768dbf02d" xlink:to="loc_us-gaap_DeferredIncomeTaxLiabilitiesNet_312bb08b-3f8e-457f-b631-894312f4a23b" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesCurrent_7e3d6fd2-b204-42f5-979b-8bcd27a53563" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LiabilitiesCurrent"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_Liabilities_c314bb52-8009-4a60-a748-5e7768dbf02d" xlink:to="loc_us-gaap_LiabilitiesCurrent_7e3d6fd2-b204-42f5-979b-8bcd27a53563" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherLiabilitiesNoncurrent_7f375161-ea56-4732-b210-44ee5ced537f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherLiabilitiesNoncurrent"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_Liabilities_c314bb52-8009-4a60-a748-5e7768dbf02d" xlink:to="loc_us-gaap_OtherLiabilitiesNoncurrent_7f375161-ea56-4732-b210-44ee5ced537f" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermLineOfCredit_b17c9624-58c8-4ac7-a9a2-73ff90ce4356" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongTermLineOfCredit"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_Liabilities_c314bb52-8009-4a60-a748-5e7768dbf02d" xlink:to="loc_us-gaap_LongTermLineOfCredit_b17c9624-58c8-4ac7-a9a2-73ff90ce4356" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.ngsgi.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFOPERATIONS" xlink:type="simple" xlink:href="ngs-20240331.xsd#CONDENSEDCONSOLIDATEDSTATEMENTSOFOPERATIONS"/>
  <link:calculationLink xlink:role="http://www.ngsgi.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFOPERATIONS" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_2a6b06ad-7e47-4cb7-8bcd-ee75a84d084a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingIncomeLoss_cf9cfec9-209d-4b39-8cdf-363a21359a3d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OperatingIncomeLoss"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_2a6b06ad-7e47-4cb7-8bcd-ee75a84d084a" xlink:to="loc_us-gaap_OperatingIncomeLoss_cf9cfec9-209d-4b39-8cdf-363a21359a3d" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonoperatingIncomeExpense_7da0177a-b2ea-42c6-9797-b5fa730ed8a9" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NonoperatingIncomeExpense"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_2a6b06ad-7e47-4cb7-8bcd-ee75a84d084a" xlink:to="loc_us-gaap_NonoperatingIncomeExpense_7da0177a-b2ea-42c6-9797-b5fa730ed8a9" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonoperatingIncomeExpense_2cc25966-613f-435d-89cf-05781e8b7bbb" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NonoperatingIncomeExpense"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpense_89f6e666-a7f2-48d9-b337-a3d3b50f10bd" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InterestExpense"/>
    <link:calculationArc order="1" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NonoperatingIncomeExpense_2cc25966-613f-435d-89cf-05781e8b7bbb" xlink:to="loc_us-gaap_InterestExpense_89f6e666-a7f2-48d9-b337-a3d3b50f10bd" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherNonoperatingIncomeExpense_560e89cc-bfec-43d8-9446-dbb977caeaef" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherNonoperatingIncomeExpense"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NonoperatingIncomeExpense_2cc25966-613f-435d-89cf-05781e8b7bbb" xlink:to="loc_us-gaap_OtherNonoperatingIncomeExpense_560e89cc-bfec-43d8-9446-dbb977caeaef" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostsAndExpenses_d4e0ee8e-1511-40cf-8bdf-a3aa7eccd803" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CostsAndExpenses"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DirectCostsOfLeasedAndRentedPropertyOrEquipment_74fcadc7-bbc2-4f65-8705-92f2ce100833" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DirectCostsOfLeasedAndRentedPropertyOrEquipment"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_CostsAndExpenses_d4e0ee8e-1511-40cf-8bdf-a3aa7eccd803" xlink:to="loc_us-gaap_DirectCostsOfLeasedAndRentedPropertyOrEquipment_74fcadc7-bbc2-4f65-8705-92f2ce100833" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostOfPropertyRepairsAndMaintenance_9f8b9ee5-9b71-4603-8a72-e518cb136b9d" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CostOfPropertyRepairsAndMaintenance"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_CostsAndExpenses_d4e0ee8e-1511-40cf-8bdf-a3aa7eccd803" xlink:to="loc_us-gaap_CostOfPropertyRepairsAndMaintenance_9f8b9ee5-9b71-4603-8a72-e518cb136b9d" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SellingGeneralAndAdministrativeExpense_551afad3-c8c8-4848-b721-5838f82b228a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SellingGeneralAndAdministrativeExpense"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_CostsAndExpenses_d4e0ee8e-1511-40cf-8bdf-a3aa7eccd803" xlink:to="loc_us-gaap_SellingGeneralAndAdministrativeExpense_551afad3-c8c8-4848-b721-5838f82b228a" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DepreciationDepletionAndAmortization_86d2fcd4-81d9-4917-b315-6ec69a645fd3" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DepreciationDepletionAndAmortization"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_CostsAndExpenses_d4e0ee8e-1511-40cf-8bdf-a3aa7eccd803" xlink:to="loc_us-gaap_DepreciationDepletionAndAmortization_86d2fcd4-81d9-4917-b315-6ec69a645fd3" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherCostOfOperatingRevenue_f9dc1373-bac2-4011-bdc3-e691ca390035" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherCostOfOperatingRevenue"/>
    <link:calculationArc order="5" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_CostsAndExpenses_d4e0ee8e-1511-40cf-8bdf-a3aa7eccd803" xlink:to="loc_us-gaap_OtherCostOfOperatingRevenue_f9dc1373-bac2-4011-bdc3-e691ca390035" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ImpairedAssetsToBeDisposedOfByMethodOtherThanSaleAmountOfImpairmentLoss_7e543484-db6d-4b0f-a524-338f12e896e1" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ImpairedAssetsToBeDisposedOfByMethodOtherThanSaleAmountOfImpairmentLoss"/>
    <link:calculationArc order="6" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_CostsAndExpenses_d4e0ee8e-1511-40cf-8bdf-a3aa7eccd803" xlink:to="loc_us-gaap_ImpairedAssetsToBeDisposedOfByMethodOtherThanSaleAmountOfImpairmentLoss_7e543484-db6d-4b0f-a524-338f12e896e1" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Revenues_5ac8797e-f098-4387-bebb-c7783dd31739" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_Revenues"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RentalIncomeNonoperating_139b4c83-5308-43a1-a59b-afedd7c50724" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RentalIncomeNonoperating"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_Revenues_5ac8797e-f098-4387-bebb-c7783dd31739" xlink:to="loc_us-gaap_RentalIncomeNonoperating_139b4c83-5308-43a1-a59b-afedd7c50724" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_85c8aee6-394d-4120-b4cb-6deba76bb8e2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_Revenues_5ac8797e-f098-4387-bebb-c7783dd31739" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_85c8aee6-394d-4120-b4cb-6deba76bb8e2" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingIncomeLoss_03669534-8dcb-41c0-9a4a-a6e6f14f7594" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OperatingIncomeLoss"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Revenues_6981b4a4-a641-4df1-a440-b968bba50aae" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_Revenues"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_OperatingIncomeLoss_03669534-8dcb-41c0-9a4a-a6e6f14f7594" xlink:to="loc_us-gaap_Revenues_6981b4a4-a641-4df1-a440-b968bba50aae" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostsAndExpenses_c6fa8d60-4da7-4a9c-8574-650e4c51c200" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CostsAndExpenses"/>
    <link:calculationArc order="2" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_OperatingIncomeLoss_03669534-8dcb-41c0-9a4a-a6e6f14f7594" xlink:to="loc_us-gaap_CostsAndExpenses_c6fa8d60-4da7-4a9c-8574-650e4c51c200" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_f03b999d-6b13-40f9-85c9-d317289d42c8" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetIncomeLoss"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_0bda74e7-dbf8-487f-9f10-cc94fe37f868" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetIncomeLoss_f03b999d-6b13-40f9-85c9-d317289d42c8" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_0bda74e7-dbf8-487f-9f10-cc94fe37f868" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxExpenseBenefit_e99f581d-879b-4bd3-ba0d-d3624a7654b0" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeTaxExpenseBenefit"/>
    <link:calculationArc order="2" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetIncomeLoss_f03b999d-6b13-40f9-85c9-d317289d42c8" xlink:to="loc_us-gaap_IncomeTaxExpenseBenefit_e99f581d-879b-4bd3-ba0d-d3624a7654b0" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.ngsgi.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFCASHFLOWS" xlink:type="simple" xlink:href="ngs-20240331.xsd#CONDENSEDCONSOLIDATEDSTATEMENTSOFCASHFLOWS"/>
  <link:calculationLink xlink:role="http://www.ngsgi.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFCASHFLOWS" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_74ecbd7e-1218-4e52-848b-2bf619325260" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_b187b3ac-f0dd-4100-8e53-41e42fe05efd" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivities"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_74ecbd7e-1218-4e52-848b-2bf619325260" xlink:to="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_b187b3ac-f0dd-4100-8e53-41e42fe05efd" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_46eb9b1b-8f15-41ae-8448-8ffb63342515" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetCashProvidedByUsedInInvestingActivities"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_74ecbd7e-1218-4e52-848b-2bf619325260" xlink:to="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_46eb9b1b-8f15-41ae-8448-8ffb63342515" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_28ecb7e8-43cd-4e27-94e4-3cabcef57307" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivities"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_74ecbd7e-1218-4e52-848b-2bf619325260" xlink:to="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_28ecb7e8-43cd-4e27-94e4-3cabcef57307" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_81f23c5d-a568-41e5-98ef-ddf857a1e38f" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivities"/>
    <link:loc xlink:type="locator" xlink:label="loc_ngs_PaymentsForOtherLongTermLiabilitiesNet_09b22517-5011-42a0-86be-e55b895a4be6" xlink:href="ngs-20240331.xsd#ngs_PaymentsForOtherLongTermLiabilitiesNet"/>
    <link:calculationArc order="1" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_81f23c5d-a568-41e5-98ef-ddf857a1e38f" xlink:to="loc_ngs_PaymentsForOtherLongTermLiabilitiesNet_09b22517-5011-42a0-86be-e55b895a4be6" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsOfDebtIssuanceCosts_38f64fee-ba81-47b7-b7c7-9d40de2405fd" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PaymentsOfDebtIssuanceCosts"/>
    <link:calculationArc order="2" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_81f23c5d-a568-41e5-98ef-ddf857a1e38f" xlink:to="loc_us-gaap_PaymentsOfDebtIssuanceCosts_38f64fee-ba81-47b7-b7c7-9d40de2405fd" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsRelatedToTaxWithholdingForShareBasedCompensation_8d4afda1-184d-4870-ab04-ccc5b4d48e0a" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PaymentsRelatedToTaxWithholdingForShareBasedCompensation"/>
    <link:calculationArc order="3" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_81f23c5d-a568-41e5-98ef-ddf857a1e38f" xlink:to="loc_us-gaap_PaymentsRelatedToTaxWithholdingForShareBasedCompensation_8d4afda1-184d-4870-ab04-ccc5b4d48e0a" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromIssuanceOfLongTermDebt_5b6f0742-bfa9-46e1-a425-c159050121c2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ProceedsFromIssuanceOfLongTermDebt"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_81f23c5d-a568-41e5-98ef-ddf857a1e38f" xlink:to="loc_us-gaap_ProceedsFromIssuanceOfLongTermDebt_5b6f0742-bfa9-46e1-a425-c159050121c2" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_b210139a-7c83-4b49-b910-85450b5885d3" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetCashProvidedByUsedInInvestingActivities"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquirePropertyPlantAndEquipment_5be52fcb-dff6-4493-b5f9-4b1801f48524" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PaymentsToAcquirePropertyPlantAndEquipment"/>
    <link:calculationArc order="1" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_b210139a-7c83-4b49-b910-85450b5885d3" xlink:to="loc_us-gaap_PaymentsToAcquirePropertyPlantAndEquipment_5be52fcb-dff6-4493-b5f9-4b1801f48524" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquireLifeInsurancePolicies_9fab1e36-78df-4a1e-a9c2-1fc32f4f507c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PaymentsToAcquireLifeInsurancePolicies"/>
    <link:calculationArc order="2" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_b210139a-7c83-4b49-b910-85450b5885d3" xlink:to="loc_us-gaap_PaymentsToAcquireLifeInsurancePolicies_9fab1e36-78df-4a1e-a9c2-1fc32f4f507c" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_b99164fe-a5ce-492e-8721-65cd6df7dfd0" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivities"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInInventories_c266b937-b34c-4bdc-8d07-e12ecc81c0db" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncreaseDecreaseInInventories"/>
    <link:calculationArc order="1" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_b99164fe-a5ce-492e-8721-65cd6df7dfd0" xlink:to="loc_us-gaap_IncreaseDecreaseInInventories_c266b937-b34c-4bdc-8d07-e12ecc81c0db" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInAccountsPayableAndAccruedLiabilities_f95bc09d-d3ef-4093-abcd-09c9669a9245" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncreaseDecreaseInAccountsPayableAndAccruedLiabilities"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_b99164fe-a5ce-492e-8721-65cd6df7dfd0" xlink:to="loc_us-gaap_IncreaseDecreaseInAccountsPayableAndAccruedLiabilities_f95bc09d-d3ef-4093-abcd-09c9669a9245" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets_aaef1fcf-2b1a-4d96-9125-127c7929a8c0" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets"/>
    <link:calculationArc order="3" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_b99164fe-a5ce-492e-8721-65cd6df7dfd0" xlink:to="loc_us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets_aaef1fcf-2b1a-4d96-9125-127c7929a8c0" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInContractWithCustomerLiability_e9c70e18-1287-4ee1-b5d4-206c6676a354" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncreaseDecreaseInContractWithCustomerLiability"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_b99164fe-a5ce-492e-8721-65cd6df7dfd0" xlink:to="loc_us-gaap_IncreaseDecreaseInContractWithCustomerLiability_e9c70e18-1287-4ee1-b5d4-206c6676a354" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInAccountsReceivable_4aa92f27-e3e2-478c-b528-7d0821a31743" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncreaseDecreaseInAccountsReceivable"/>
    <link:calculationArc order="5" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_b99164fe-a5ce-492e-8721-65cd6df7dfd0" xlink:to="loc_us-gaap_IncreaseDecreaseInAccountsReceivable_4aa92f27-e3e2-478c-b528-7d0821a31743" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensation_fe2ed70d-35c0-4abd-99a4-ee3848a0a47c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensation"/>
    <link:calculationArc order="6" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_b99164fe-a5ce-492e-8721-65cd6df7dfd0" xlink:to="loc_us-gaap_ShareBasedCompensation_fe2ed70d-35c0-4abd-99a4-ee3848a0a47c" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LifeInsuranceCorporateOrBankOwnedChangeInValue_c40291b1-55cb-47db-ac19-28772322e170" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LifeInsuranceCorporateOrBankOwnedChangeInValue"/>
    <link:calculationArc order="7" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_b99164fe-a5ce-492e-8721-65cd6df7dfd0" xlink:to="loc_us-gaap_LifeInsuranceCorporateOrBankOwnedChangeInValue_c40291b1-55cb-47db-ac19-28772322e170" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DepreciationDepletionAndAmortization_8c89c093-4c3e-4f15-b2cc-45614b4441f2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DepreciationDepletionAndAmortization"/>
    <link:calculationArc order="8" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_b99164fe-a5ce-492e-8721-65cd6df7dfd0" xlink:to="loc_us-gaap_DepreciationDepletionAndAmortization_8c89c093-4c3e-4f15-b2cc-45614b4441f2" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInOtherCurrentAssets_04c60303-7106-4ef9-ae55-d24ceb53a2a8" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncreaseDecreaseInOtherCurrentAssets"/>
    <link:calculationArc order="9" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_b99164fe-a5ce-492e-8721-65cd6df7dfd0" xlink:to="loc_us-gaap_IncreaseDecreaseInOtherCurrentAssets_04c60303-7106-4ef9-ae55-d24ceb53a2a8" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProvisionForDoubtfulAccounts_62b34d64-f254-48b4-9fc3-28bdc48d7259" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ProvisionForDoubtfulAccounts"/>
    <link:calculationArc order="10" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_b99164fe-a5ce-492e-8721-65cd6df7dfd0" xlink:to="loc_us-gaap_ProvisionForDoubtfulAccounts_62b34d64-f254-48b4-9fc3-28bdc48d7259" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_a93a186a-5a5a-4404-9517-36418c86d9f1" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetIncomeLoss"/>
    <link:calculationArc order="11" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_b99164fe-a5ce-492e-8721-65cd6df7dfd0" xlink:to="loc_us-gaap_NetIncomeLoss_a93a186a-5a5a-4404-9517-36418c86d9f1" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AmortizationOfFinancingCosts_10798992-91dd-436b-8ebf-b1c929b6aec9" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AmortizationOfFinancingCosts"/>
    <link:calculationArc order="12" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_b99164fe-a5ce-492e-8721-65cd6df7dfd0" xlink:to="loc_us-gaap_AmortizationOfFinancingCosts_10798992-91dd-436b-8ebf-b1c929b6aec9" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainLossOnDispositionOfAssets_ec601622-54da-48e2-b056-37d92901ea2e" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_GainLossOnDispositionOfAssets"/>
    <link:calculationArc order="13" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_b99164fe-a5ce-492e-8721-65cd6df7dfd0" xlink:to="loc_us-gaap_GainLossOnDispositionOfAssets_ec601622-54da-48e2-b056-37d92901ea2e" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredIncomeTaxExpenseBenefit_dc275fe0-481b-40c4-b36d-f850321e292b" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DeferredIncomeTaxExpenseBenefit"/>
    <link:calculationArc order="14" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_b99164fe-a5ce-492e-8721-65cd6df7dfd0" xlink:to="loc_us-gaap_DeferredIncomeTaxExpenseBenefit_dc275fe0-481b-40c4-b36d-f850321e292b" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ImpairedAssetsToBeDisposedOfByMethodOtherThanSaleAmountOfImpairmentLoss_4bf2744f-a7e8-4288-8e4a-bafd2e1d479c" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ImpairedAssetsToBeDisposedOfByMethodOtherThanSaleAmountOfImpairmentLoss"/>
    <link:calculationArc order="15" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_b99164fe-a5ce-492e-8721-65cd6df7dfd0" xlink:to="loc_us-gaap_ImpairedAssetsToBeDisposedOfByMethodOtherThanSaleAmountOfImpairmentLoss_4bf2744f-a7e8-4288-8e4a-bafd2e1d479c" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.ngsgi.com/role/SummaryofSignificantAccountingPoliciesScheduleofContractwithCustomerAssetandLiabilityDetails" xlink:type="simple" xlink:href="ngs-20240331.xsd#SummaryofSignificantAccountingPoliciesScheduleofContractwithCustomerAssetandLiabilityDetails"/>
  <link:calculationLink xlink:role="http://www.ngsgi.com/role/SummaryofSignificantAccountingPoliciesScheduleofContractwithCustomerAssetandLiabilityDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsReceivableNetCurrent_cf5d89ed-6adc-4188-8722-fe432761aca8" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccountsReceivableNetCurrent"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsReceivableGrossCurrent_91474b3e-33b8-4702-b86e-3a0d56833fd2" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccountsReceivableGrossCurrent"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_AccountsReceivableNetCurrent_cf5d89ed-6adc-4188-8722-fe432761aca8" xlink:to="loc_us-gaap_AccountsReceivableGrossCurrent_91474b3e-33b8-4702-b86e-3a0d56833fd2" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllowanceForDoubtfulAccountsReceivableCurrent_0795ecea-151f-4fd9-af8e-b5c1d86639f5" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AllowanceForDoubtfulAccountsReceivableCurrent"/>
    <link:calculationArc order="2" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_AccountsReceivableNetCurrent_cf5d89ed-6adc-4188-8722-fe432761aca8" xlink:to="loc_us-gaap_AllowanceForDoubtfulAccountsReceivableCurrent_0795ecea-151f-4fd9-af8e-b5c1d86639f5" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsReceivableGrossCurrent_5c12dfb0-50c6-4da0-8a05-3451d52cff30" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccountsReceivableGrossCurrent"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerAssetNetCurrent_c6fd42e1-651d-4f0b-ba98-7a3556c6f2ae" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ContractWithCustomerAssetNetCurrent"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_AccountsReceivableGrossCurrent_5c12dfb0-50c6-4da0-8a05-3451d52cff30" xlink:to="loc_us-gaap_ContractWithCustomerAssetNetCurrent_c6fd42e1-651d-4f0b-ba98-7a3556c6f2ae" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_ngs_AccountsReceivableExcludingContractsWithCustomerAssetCurrent_27587ef8-786d-406b-b5b5-5dd46cdef6d2" xlink:href="ngs-20240331.xsd#ngs_AccountsReceivableExcludingContractsWithCustomerAssetCurrent"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_AccountsReceivableGrossCurrent_5c12dfb0-50c6-4da0-8a05-3451d52cff30" xlink:to="loc_ngs_AccountsReceivableExcludingContractsWithCustomerAssetCurrent_27587ef8-786d-406b-b5b5-5dd46cdef6d2" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.ngsgi.com/role/InventoryScheduleofInventoryDetails" xlink:type="simple" xlink:href="ngs-20240331.xsd#InventoryScheduleofInventoryDetails"/>
  <link:calculationLink xlink:role="http://www.ngsgi.com/role/InventoryScheduleofInventoryDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InventoryNet_51f11c95-3817-4673-ba5e-825ab60693b7" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InventoryNet"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InventoryFinishedGoodsNetOfReserves_a5642e36-b3ac-4c29-882c-37a381bced65" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InventoryFinishedGoodsNetOfReserves"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_InventoryNet_51f11c95-3817-4673-ba5e-825ab60693b7" xlink:to="loc_us-gaap_InventoryFinishedGoodsNetOfReserves_a5642e36-b3ac-4c29-882c-37a381bced65" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InventoryWorkInProcessNetOfReserves_9f7a5698-c3b6-46a2-8eef-15a83ed30b62" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InventoryWorkInProcessNetOfReserves"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_InventoryNet_51f11c95-3817-4673-ba5e-825ab60693b7" xlink:to="loc_us-gaap_InventoryWorkInProcessNetOfReserves_9f7a5698-c3b6-46a2-8eef-15a83ed30b62" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_ngs_InventoryNetOfReserves_5bdbb9b9-af8a-4f31-a5f7-111a000629cb" xlink:href="ngs-20240331.xsd#ngs_InventoryNetOfReserves"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InventoryRawMaterialsNetOfReserves_e5b23ea4-df0e-402b-88e3-424987c0a7cf" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InventoryRawMaterialsNetOfReserves"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_ngs_InventoryNetOfReserves_5bdbb9b9-af8a-4f31-a5f7-111a000629cb" xlink:to="loc_us-gaap_InventoryRawMaterialsNetOfReserves_e5b23ea4-df0e-402b-88e3-424987c0a7cf" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InventoryNet_0120fe57-c844-4221-b21d-9956dfaf8acb" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InventoryNet"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_ngs_InventoryNetOfReserves_5bdbb9b9-af8a-4f31-a5f7-111a000629cb" xlink:to="loc_us-gaap_InventoryNet_0120fe57-c844-4221-b21d-9956dfaf8acb" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.ngsgi.com/role/RentalEquipmentDetails" xlink:type="simple" xlink:href="ngs-20240331.xsd#RentalEquipmentDetails"/>
  <link:calculationLink xlink:role="http://www.ngsgi.com/role/RentalEquipmentDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_ngs_RentalEquipmentNet_e646765f-c1c3-4759-bbd4-40f362ed822b" xlink:href="ngs-20240331.xsd#ngs_RentalEquipmentNet"/>
    <link:loc xlink:type="locator" xlink:label="loc_ngs_RentalEquipmentGross_c69be0f6-43cb-448a-986c-3ecd61ed8a77" xlink:href="ngs-20240331.xsd#ngs_RentalEquipmentGross"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_ngs_RentalEquipmentNet_e646765f-c1c3-4759-bbd4-40f362ed822b" xlink:to="loc_ngs_RentalEquipmentGross_c69be0f6-43cb-448a-986c-3ecd61ed8a77" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_ngs_RentalEquipmentAccumulatedDepreciation_d6ba43ed-749f-4e66-8416-af3d1234a718" xlink:href="ngs-20240331.xsd#ngs_RentalEquipmentAccumulatedDepreciation"/>
    <link:calculationArc order="2" weight="-1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_ngs_RentalEquipmentNet_e646765f-c1c3-4759-bbd4-40f362ed822b" xlink:to="loc_ngs_RentalEquipmentAccumulatedDepreciation_d6ba43ed-749f-4e66-8416-af3d1234a718" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.ngsgi.com/role/EarningslossperShareDetails" xlink:type="simple" xlink:href="ngs-20240331.xsd#EarningslossperShareDetails"/>
  <link:calculationLink xlink:role="http://www.ngsgi.com/role/EarningslossperShareDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_cbdd760b-8551-4592-93bb-6dcd5e885660" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_605a29f9-46ff-40c9-91e8-061885794620" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingBasic"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_cbdd760b-8551-4592-93bb-6dcd5e885660" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_605a29f9-46ff-40c9-91e8-061885794620" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements_34f982b1-814a-4f87-a876-daaaedfe8651" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_cbdd760b-8551-4592-93bb-6dcd5e885660" xlink:to="loc_us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements_34f982b1-814a-4f87-a876-daaaedfe8651" xlink:type="arc"/>
  </link:calculationLink>
</link:linkbase>
