EX-4.2





 Exhibit 4.2 

AMENDMENT OF 
 WARRANT
AGREEMENT 
 THIS AMENDMENT OF WARRANT AGREEMENT (this “Agreement”), made as of August 25, 2021, is made by
and among Rocket Lab USA, Inc. (f/k/a Vector Acquisition Corporation), a Delaware corporation (the “Company,” and prior to the Closing (as defined below), “Vector”), Continental Stock Transfer &
Trust Company, a New York corporation, as warrant agent (“Continental”), and American Stock Transfer & Trust Company, a New York corporation (“AST”). 

WHEREAS, the Company and Continental are parties to that certain Warrant Agreement (the “Existing Warrant Agreement”), dated
as of September 24, 2020, pursuant to which the Company issued 10,666,666 warrants (the “Public Warrants”) in its initial public offering and 5,600,000 private placement warrants (“Private Placement Warrants”,
together with the Public Warrants, the “Warrants”), each representing the right to purchase one share of common stock, par value $0.0001 per share, of the Company; 

WHEREAS, capitalized terms used herein, but not otherwise defined, shall have the meanings given to such terms in the Existing Warrant
Agreement; 
 WHEREAS, effective as of March 1, 2021, the Company entered into an Agreement and Plan of Merger (the “Merger
Agreement”) by and among Rocket Lab USA, Inc. (“Old Rocket Lab”), Prestige USA Merger Sub, Inc., a Delaware corporation and direct wholly owned subsidiary of Old Rocket Lab, and Vector; 

WHEREAS, the transactions contemplated by the Merger Agreement closed on the date of this Agreement (the “Closing”); 

WHEREAS, Continental has agreed to resign its duties as the Warrant Agent as of the date hereof, and AST has agreed to serve as successor
Warrant Agent from and after the date hereof; and 
 WHEREAS, pursuant to Section 9.8 of the Existing Warrant Agreement, the parties
may, under certain circumstances, including those contemplated by this Agreement, amend the Existing Warrant Agreement without the consent of the Registered Holders. 

NOW, THEREFORE, in consideration of the mutual agreements contained herein and other good and valuable consideration, the receipt and
sufficiency of which are hereby acknowledged, and intending to be legally bound hereby, the parties hereto agree as follows: 

1.    Amendment of Existing Warrant Agreement. The parties hereby amend, effective as of the date of
this Agreement, the Existing Warrant Agreement as provided in this Section 1. 
 a.    
Change in Warrant Agent Amendment. References to “Continental Stock Transfer & Trust Company” in the Existing Warrant Agreement shall be replaced with “American Stock Transfer & Trust Company”. 












 b.     Change of Address of Warrant Agent. Section 9.2 of
the Existing Warrant Agreement is hereby amended to direct that any notice, statement or demand authorized by the Existing Warrant Agreement to be given or made by the Warrant Agent or by the holder of any Warrant to or on the Company pursuant to
Section 9.2 shall be delivered to: 
 American Stock Transfer & Trust Company 

6201 15th Avenue 

Brooklyn, NY 11219 
 Email:
Reorgwarrants@astfinancial.com 
 c.     Change of Address of Company. Section 9.2 of
the Existing Warrant Agreement is hereby amended to direct that any notice, statement or demand authorized by this Agreement to be given or made by the Warrant Agent or by the holder of any Warrant to or on the Company pursuant to Section 9.2
shall be delivered to: 
 Rocket Lab USA, Inc. 

3881 McGowen Street 
 Long Beach,
CA, USA 90808 
 Attn: Robbie Hurwitz 

Email: r.hurwitz@rocketlabusa.com 

With a copy to: 
 Goodwin
Procter LLP 
 601 Marshall St. 

Redwood City, CA 94063 
 Attn:
Stuart Ogg 
 Email: sogg@goodwinlaw.com 

2.    Warrant Agent Succession and Resignation of Current Warrant Agent and Appointment of Successor.
Continental hereby resigns as Warrant Agent, and the Company hereby appoints AST to act as the Warrant Agent for the Company for the Warrants, and AST hereby accepts such appointment and agrees to perform the same in accordance with the terms
and conditions set forth in the Existing Warrant Agreement as modified by this Agreement. 
 3.    Miscellaneous
Provisions. 
 a.     Successors. All the covenants and provisions of this Agreement by or for the
benefit of the parties shall bind and inure to the benefit of their respective successors and assigns. 
 b.    
Applicable Law. The validity, interpretation, and performance of this Agreement shall be governed in all respects by the laws of the State of New York, without giving effect to conflicts of law principles that would result in the
application of the substantive laws of another jurisdiction. The Company hereby agrees that any action, proceeding or claim against it arising out of or relating in any way to this Agreement shall be brought and enforced in the courts of the State
of New York or the United States District Court for the Southern District of New York, and irrevocably submits to such jurisdiction, which jurisdiction shall be exclusive. The Company hereby waives any objection to such exclusive jurisdiction and
that such courts represent an inconvenient forum. 












 c.     Counterparts. This Agreement may be executed in any number
of original or facsimile counterparts and each of such counterparts shall for all purposes be deemed to be an original, and all such counterparts shall together constitute but one and the same instrument. 

d.     Effect of Headings. The section headings herein are for convenience only and are not part of this Agreement
and shall not affect the interpretation thereof. 
 e.     Severability. This Agreement shall be deemed
severable, and the invalidity or unenforceability of any term or provision hereof shall not affect the validity or enforceability of this Agreement or of any other term or provision hereof. Furthermore, in lieu of any such invalid or unenforceable
term or provision, the parties hereto intend that there shall be added as a part of this Agreement a provision as similar in terms to such invalid or unenforceable provision as may be possible and be valid and enforceable. 

f.     Entire Agreement. The Existing Warrant Agreement, as modified by this Agreement, constitutes the entire
understanding of the parties and supersedes all prior agreements, understandings, arrangements, promises and commitments, whether written or oral, express or implied, relating to the subject matter hereof, and all such prior agreements,
understandings, arrangements, promises and commitments are hereby canceled and terminated. 
 [Signature page follows] 












 IN WITNESS WHEREOF, the parties hereto have caused this Agreement to be duly
executed as of the date first above written. 
  

					
	ROCKET LAB USA, INC.
		
	By:	 	 /s/ Peter
Beck                        

		 	Name:	 	Peter Beck
		 	Title:	 	President
	
	CONTINENTAL STOCK TRANSFER & TRUST COMPANY
		
	By:	 	 /s/ Ana Gois

		 	Name:	 	Ana Gois
		 	Title:	 	Vice President
	
	AMERICAN STOCK TRANSFER & TRUST COMPANY
		
	By:	 	 /s/ Michael A. Nespoli

		 	Name:	 	Michael A. Nespoli
		 	Title:	 	Executive Director



  
 [Signature Page to
Amendment of Warrant Agreement]