Cover Page	3 Months Ended
	Mar. 31, 2022 shares
Document Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Mar. 31, 2022
Document Transition Report	false
Entity File Number	001-39128
Entity Registrant Name	Momentus Inc.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	84-1905538
Entity Address, Address Line One	3901 N. First Street
Entity Address, City or Town	San Jose
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	95134
City Area Code	650
Local Phone Number	564-7820
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Smaller Reporting Company	true
Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding	81,755,715
Entity Central Index Key	0001781162
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2022
Document Fiscal Period Focus	Q1
Amendment Flag	false
Class A common stock
Document Information [Line Items]
Title of 12(b) Security	Class A common stock
Trading Symbol	MNTS
Security Exchange Name	NASDAQ
Warrants
Document Information [Line Items]
Title of 12(b) Security	Warrants
Trading Symbol	MNTSW
Security Exchange Name	NASDAQ