# Project 4023 — Expeditionary Underwater Systems

**Program element:** 0604536N — Advanced Undersea Prototyping  
**Project:** 4023  
**Component:** U.S. Navy  
**Appropriation:** 1319 — RDT&E, Navy  
**Budget Activity:** 4 — Advanced Component Development & Prototypes  
**Vintage:** President's Budget PB2027  
**Canonical URL:** https://hitchintel.com/programs/0604536N/4023  
**Parent:** https://hitchintel.com/programs/0604536N

## Summary

Project 4023 — Expeditionary Underwater Systems requests $17.6M in FY2027, 11% of the $164.5M requested for program element 0604536N — a new start, with no prior-year and no current-year money. 3 R-2A activities decompose the request, 3 new this cycle. HI is the largest named R-3 performer at $1.6M, 9.0% of the project's FY2027 R-3 total.

## Funding profile

| Fiscal Year | Estimate Type | Amount ($M) |
|---|---|---|
| FY2025 | Actual | 0.0 |
| FY2026 | Enacted | 0.0 |
| FY2027 | Request | 17.6 |
| FY2028 | Outyear | 16.9 |
| FY2029 | Outyear | 16.2 |
| FY2030 | Outyear | 15.1 |
| FY2031 | Outyear | 15.4 |

> Estimate types are not summed. This project is one leaf of PE 0604536N; the PE total is the sum of its projects, never added to them.

## What project 4023 buys

The MK18 Expeditionary Unmanned Underwater Vehicle (UUV) programs represent a critical portfolio of capabilities, directly supporting the Chief of Naval Operations' (CNO) strategy to hedge our forces against evolving maritime threats. This portfolio is centered on a dynamic approach of integrating, experimenting with, and maturing advanced technologies to ensure a persistent undersea advantage. The MK18 Expeditionary UUV programs develop, field and sustain advanced and highly portable UUVs to support a variety of critical naval missions. The Family of Systems consists of the fielded MK 18 MOD 1 Swordfish small UUV and MK 18 MOD 2 Kingfish medium UUV, both in sustainment. The MK 18 family also consists of the next generation cybersecure MK 18 MOD 3 Lionfish, currently in full rate production and intended as a small UUV replacement to the MK 18 MOD 1. The Lionfish has greater endurance, depth, sensor, autonomy, cybersecurity and other improvements over the Swordfish. Finally, the MK 18 family consists of the MK 18 MOD 4 Viperfish, currently in development and test/evaluation, and intended as a more capable and more expeditionary deep water UUV replacement to the larger MK 18 MOD 2. The Viperfish smaller size allows launch, recovery and movement from a much larger host of platforms, to include the 9-meter Rigid Hull Inflatable Boat, and will leverage volume and bottom minehunting at the same or deeper depths as the larger legacy MK 18 MOD 2. These programs provide required unmanned capabilities to expeditionary forces such as Explosive Ordnance Disposal (EOD) platoons, Expeditionary Mine Countermeasures (ExMCM) companies, Mobile Diving and Salvage units, Naval Special Warfare forces, USMC Littoral forces, and UUV Squadrons. They provide a safe and effective means to conduct mine countermeasures, surveillance, and intelligence gathering; enabling the remote detection and neutralization of underwater threats like mines and IEDs, and the detection, classification and localization of other items of interest. They directly support fleet battle group maneuver through key maritime terrain both in deep water and in chokepoints, along with contested logistics, Maritime Homeland Defense, and amphibious operations.

**R-3 lines of work:** Product Development; Support; Test and Evaluation; Management Services.

## Named R-3 performers

| Performer | $M | Share of this project's FY2027 R-3 total |
|---|---|---|
| HI | 1.6 | 9.0% |

> Budget-justification contract funding, not obligations. Shares need not reach 100% — unnamed and government work is in the denominator.

## Activities (R-2A) — 3

| Activity | FY2025 | FY2026 | FY2027 | Move | Page |
|---|---|---|---|---|---|
| Lionfish | 0.0 | 0.0 | 10.8 | new | [a1](https://hitchintel.com/programs/0604536N/4023/a1) |
| Viperfish | 0.0 | 0.0 | 5.7 | new | — |
| Swordfish and Kingfish | 0.0 | 0.0 | 1.2 | new | — |

> Activities carry the prior, current and budget year only — no five-year plan. In the request year they partition this project exactly; in earlier years they can under-cover it.

### Lionfish — NEW START

FY 2027 continues fielding baseline Lionfish production units with spiral software upgrades as required. Funding will provide additional investments in the transition of advanced technologies. Efforts will include continued development and evaluation of artificial intelligence/machine learning algorithms, advanced autonomy behaviors and…

Full year-by-year narrative: https://hitchintel.com/programs/0604536N/4023/a1

### Viperfish — NEW START

**FY2027 planned work.** Viperfish efforts will include continued in water test and evaluation of EDM vehicles with FLS9, in stride with software improvements and Automated Target Recognition development, in support of an in water capability demonstration in 3QFY27. Efforts will focus on improving forward looking sonar detection and localization accuracy of in volume contacts for successful handoff to other robotic systems for neutralization. Development efforts will also include focus on deep water propulsion and navigational accuracy alternatives to reduce risk in key technical areas and provide planned improvements to cut in to proposed baseline deep water configurations. Investments will continue in AI/ML technologies and ATR algorithms to shorten detect-to-engage timelines, increase probability of detection, and optimize machine-Sailor teaming.

**FY2026 to FY2027 change.** The increase in RDTE reflects the updated acquisition strategy for Viperfish, which utilizes a similar vehicle and sensors as the Lionfish. This utilization of parallel RDTE efforts for Lionfish enables the Viperfish project to cut in mature technology from Lionfish RDTE efforts to the Viperfish when ready for transition.

**FY2026 plans — current year.** Viperfish efforts will include EDM delivery, GFE Front Nose Sections/FLS09 EDM integration and test, in water testing and evaluation, software maturation and Automated Target Recognition development. EDM units will commence Contractor Quality Acceptance Testing (QAT) and Government Design Verification Testing (DVT). Efforts also provide updates to autonomy , planning, Post Mission Analysis (PMA), deep hunt actions and tools. Funding supports continued development and testing of advanced technologies that will allow warfighters to detect, classify, and localize high priority threats in meeting mine and undersea warfare missions. Investments will continue in Artificial Intelligence and Machine Learning (AI/ML) technologies, as well as continued improvements in Automated Target Recognition (ATR) algorithms, more advanced autonomy architecture and enhancements to acoustic and electro-optic sensor performance. This program was apart of PE 0604028N in FY26.

### Swordfish and Kingfish — NEW START

**FY2027 planned work.** FY 2027 efforts include fleet demonstration of the fielded deep water capability for volume and bottom target search/classify/map missions, and continued engineering change proposals with hardware and software upgrades as required to sustain the MK 18 MOD 1 and MOD 2 fleets until replaced by the next generation expeditionary UUVs.

**FY2026 to FY2027 change.** The decrease in funding from FY 2026 to FY 2027 is due to an overall decrease in DT&E efforts as the deep water capability is fully fielded, and the program enters into a small but steady amount of funding for continued engineering change proposal development.

**FY2026 plans — current year.** FY 2026 continues final acceptance testing and integration of the V2 ASPs, followed by fleet delivery and associated software release deployment. At sea deep water testing and evaluation of both the V1 and V2 FLS ASPs will continue, as technical teams prepare to transition those deep water capabilities to operational forces

## What is NOT on this page

Congressional marks, the R-2 mission description and acquisition strategy, the industry vs government split of the whole request, and related program elements are recorded at **program-element** grain — an NDAA mark lands on a PE, never on a project. They are at https://hitchintel.com/programs/0604536N.

## Source & machine access

- **Source:** FY2027 Department of the Navy RDT&E Budget Justification, Exhibits R-2/R-2A/R-3, PE 0604536N project 4023 (PB PB2027).
- **MCP:** `mcp.hitchintel.com` — `budget_get_program_element(pe="0604536N")`.

*HitchAI is an independent intelligence service, not affiliated with the U.S. Department of Defense. Budget figures are requests/estimates, not obligations.*