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Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
Originator-Key-Asymmetric:
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 TWSM7vrzLADbmYQaionwg5sDW3P6oaM5D3tdezXMm7z1T+B+twIDAQAB
MIC-Info: RSA-MD5,RSA,
 JrMjHES7DEL/Re6uBLMSP6mMmSps10nF15lzERCNXzVW0UNV1M3Azy0K/dtGXdx/
 72vNiYuKmRPmcljR8Ea0Sg==

<SEC-DOCUMENT>0000908662-04-000233.txt : 20041015
<SEC-HEADER>0000908662-04-000233.hdr.sgml : 20041015
<ACCEPTANCE-DATETIME>20041015165408
ACCESSION NUMBER:		0000908662-04-000233
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20041013
FILED AS OF DATE:		20041015
DATE AS OF CHANGE:		20041015

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			ADIK STEPHEN P
		CENTRAL INDEX KEY:			0001205202

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-16171
		FILM NUMBER:		041081536

	BUSINESS ADDRESS:	
		STREET 1:		801 E 86TH AVENUE
		CITY:			MERRILLVILLE
		STATE:			IN
		ZIP:			46410
		BUSINESS PHONE:		219 791 4300 EXT 224

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			BEACON POWER CORP
		CENTRAL INDEX KEY:			0001103345
		STANDARD INDUSTRIAL CLASSIFICATION:	ELECTRIC SERVICES [4911]
		IRS NUMBER:				043372365
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		234 BALLARDVALE ST
		CITY:			WILMINGTON
		STATE:			MA
		ZIP:			01887
		BUSINESS PHONE:		9786949121

	MAIL ADDRESS:	
		STREET 1:		234 BALLARDVALE ST
		CITY:			WILMINGTON
		STATE:			MA
		ZIP:			01887
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>edgar.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2004-10-13</periodOfReport>

    <issuer>
        <issuerCik>0001103345</issuerCik>
        <issuerName>BEACON POWER CORP</issuerName>
        <issuerTradingSymbol>BCON</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001205202</rptOwnerCik>
            <rptOwnerName>ADIK STEPHEN P</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O BEACON POWER CORPORATION</rptOwnerStreet1>
            <rptOwnerStreet2>234 BALLARDVALE STREET</rptOwnerStreet2>
            <rptOwnerCity>WILMINGTON</rptOwnerCity>
            <rptOwnerState>MA</rptOwnerState>
            <rptOwnerZipCode>01887</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Stock Option (Right to Buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>.74</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2004-10-13</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>100000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <value>2004-12-31</value>
            </exerciseDate>
            <expirationDate>
                <value>2014-10-13</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>100000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>100000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Grant of Option</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>Stephen P. Adik</signatureName>
        <signatureDate>2004-10-14</signatureDate>
    </ownerSignature>
</ownershipDocument>

</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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