Solicitation
Fox Tail
Dept of Defense · Defense Advanced Research Projects Agency (DARPA) · Sol. DARPA-PS-26-136
Due in 111 days
Track this notice by email. We'll email you if it's amended or awarded, and a week and two days before responses are due.
AI summary Beta
Some details weren't available to this summary, so it may miss requirements. Check the attachments on SAM.gov.
DARPA's Defense Sciences Office wants research proposals on extreme-scale hydrodynamics: first-principles computer and theory models of violent seawater events such as high-amplitude waves, very high Reynolds number flows and abrupt phase changes. It plans multiple awards as Other Transaction (OT) prototype agreements over 18 months. This is a classified SECRET-level program, and the real technical requirements are only in a classified addendum.
Watch out for
- Classified SECRET program. You need a facility clearance, safeguarding capability and cleared staff (or a path to them before award), and even the technical instructions are only released to cleared recipients.
Fox Tail is a classified program operating at the SECRET level.
- Key requirements are in a classified addendum. Metrics, schedule, milestones, deliverables and technical proposal format are not public, so you cannot judge fit or effort without first getting the addendum.
Details on the program schedule are included in the classified addendum.
- Early classified-abstract deadlines. Notice of intent is due October 30, 2026 and the abstract November 13, 2026, and classified materials take at least 10 business days to arrive, so the abstract step is tight.
DARPA is not responsible for abstract or proposal submission delays due to late requests.
- Non-conforming if metrics are not supported. Proposals without enough data, analysis or proof showing they can meet the classified metrics can be removed before evaluation.
may be considered non-conforming and removed from consideration.
- Strict IP and data rights terms. The Government requires Government Purpose Rights in program results and will not accept Background IP restrictions that hinder transition, which can be hard for firms with proprietary tools.
The Government will not accept restrictions associated with Background IP,
- Publication limits. Results may need DARPA approval before you publish anything, which matters for universities and research-driven firms.
the awardee to seek DARPA permission before publishing
- CMMC status must be in SPRS before award. Your CMMC unique identifier and annual affirmation must already be posted in SPRS, and you must vouch for your subcontractors.
the CMMC Unique Identifier (UID) associated
- Government-only research partners cannot be funded through you. If you plan to team with a national lab, FFRDC or UARC, their costs must stay out of your cost proposal and the proposal may be rejected otherwise.
may also be deemed non-conforming unless
Read from the notice and 5 attachments. 2 not read in full.
- DARPA-PS-26-136.pdf
- Attachment_J_Representations_and_Certifications.docx
- Attachment_G_Model_Other_Transaction_for_Agreement.docx
- Attachment_E_Proposal_Volume_II__Cost_Proposal_.docx
- Attachment_K_CLASSIFIED_ADDENDUM_AND_SECURITY_CLASS_GUIDE_REQUEST_FORM.docx
- Attachment_F_DARPA_Cost_Proposal_Spreadsheet.xlsx: spreadsheet: not read yet
- Attachment_I_Schedule_of_Milestones_and_Payments.xlsx: spreadsheet: not read yet
Full brief
What they want
- Innovative theory and computational models of extreme-scale hydrodynamics (high-amplitude wave propagation, very high Reynolds number flows, abrupt phase changes)
- First-principles closures of the governing laws of fluid motion, including local thermodynamic non-equilibrium effects
- Models that balance disturbance energy budgets (mechanical power, formation enthalpy, phase transformations)
- Proposals that meet the program metrics set in the classified addendum, backed by calculations, theory and data
- A classified technical volume plus an unclassified cost proposal, milestone schedule, redlined model OT and signed certifications
- Contract type
- Other Transaction (OT) for Prototype agreement, with fixed-amount milestone payments; multiple awards anticipated
- Period of performance
- 18 months: 12-month base period plus a 6-month option
- Contract vehicle
- DARPA Program Solicitation DARPA-PS-26-136 (Other Transaction authority, 10 U.S.C. 4022); not tied to a schedule or IDIQ
- How they'll choose
- Scientific review of proposals against stated criteria, listed in descending order of importance. Cost sharing may be a positive factor for efforts likely to have commercial use.
- Offers due
- Proposal due January 29, 2027, 4:00 p.m. ET. Earlier steps: notify DARPA security of intent to submit a classified abstract by October 30, 2026; abstract due November 13, 2026, 4:00 p.m.; questions close January 13, 2027, 4:00 p.m.; notify security of intent to submit a classified proposal by January 16, 2027.
- How to submit
- Classified technical volume sent through classified channels per the classified addendum; unclassified cost volume, milestone schedule, redlined model OT and certifications uploaded to DARPA's BAAT portal; unclassified questions to FoxTail@darpa.mil
- Page limits
- Cost volume has no page limit. Technical volume limits are in the classified addendum (not provided).
What they'll judge offers on
- Overall Scientific and Technical Merit
- Potential Contribution and Relevance to the DARPA Mission
- Security (the criteria text also describes this one, though the opening sentence lists only three factors)
- Cost and Schedule Realism
What to include when you submit
- Request the Security Classification Guide and classified addendum with the Attachment K form, emailed to FoxTail@darpa.mil, and allow at least 10 business days
- Email an unclassified notice of intent to submit a classified abstract and, later, a classified proposal, using the subject lines given in the solicitation
- Abstract is strongly encouraged; DARPA will say whether a full proposal is encouraged
- Volume II cost proposal in PDF or Word, 8.5 x 11 paper, 1-inch margins, 11-point font minimum, with the Attachment F cost spreadsheet as a separate editable file
- Cost proposal valid for at least 120 days, with unclassified, high-level task and milestone descriptions
- Submit the Schedule of Milestones and Payments (Attachment I), listing milestones by number only
- Submit any redlines to the model OT agreement (Attachment G)
- Complete and submit Representations and Certifications (Attachment J)
- Include a statement showing which OT-for-prototypes condition under 10 U.S.C. 4022(d)(1) is met
- State whether you view the proposed research as fundamental or not
- For CMMC, attest that subcontractors handling FCI or CUI meet the required level and describe how you will verify it
You must have
- U.S. organizations only; non-U.S. organizations and individuals cannot participate
Non-U.S. organizations and/or individuals cannot participate in this solicitation.
- Work is at the SECRET level; you need (or can obtain before award) approved cleared facilities, information systems and personnel
Fox Tail is a classified program operating at the SECRET level.
- Current CMMC Level 2 (Self-Assessment) status posted in SPRS for the prime, plus a current annual affirmation; subcontractors handling FCI or CUI must meet the required level too
CMMC Level 2 (Self-Assessment).
- To use an OT for prototypes, at least one condition must be met, such as a nontraditional defense contractor participating significantly, all significant participants being small businesses or nontraditional contractors, or one-third non-federal cost share
There is at least one nontraditional defense contractor or
- Cost sharing is not required unless you are a traditional defense contractor not working significantly with a nontraditional contractor
Cost sharing is not required unless the proposer is a traditional defense
- Active SAM registration for All Awards, and WAWF registration within 10 days of award (from the model agreement)
The Performer shall maintain an active registration for
- FFRDCs, UARCs, Government entities and National Laboratories cannot be primes and have special limits as subawardees
contractor capacity may be deemed non-conforming and not evaluated.
Not in the notice text
- Program metrics, schedule, milestones and deliverables (all in the classified addendum)
- Technical proposal format and page limits (classified addendum)
- Funding level or award size per performer
- Place of performance (blank in the notice)
- Contents of Attachment F (cost spreadsheet) and Attachment I (milestone schedule), which were not readable
- Whether Security is a fourth scored factor, since the opening sentence lists three but four are described
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Key facts
- Response due
- Jan 29, 2027, 9:00 PM UTC
- Posted
- Sep 24, 2026
- Notice type
- Solicitation
- Solicitation
- DARPA-PS-26-136
- Agency
- Dept of Defense · Defense Advanced Research Projects Agency (DARPA)
- Office
- Def Advanced Research Projects Agcy
- NAICS
- 541715
- Product/service code
- AC12
- Business type
- Engineering, architecture & research
- Contracting contact
- BAA CoordinatorFoxTail@darpa.mil
What similar contracts paid
227 contracts at this agency for the same NAICS and product/service codes had activity in the last 5 years, according to USAspending.gov. Small businesses won 15% of the dollars in this market over the last 3 fiscal years.
Typical contract$4MMiddle half: $2.5M to $5.8M
Typical per year$1.5MValue divided by years of performance
Before you respond
Full notice text from SAM.gov
The Defense Advanced Research Projects Agency (DARPA) is soliciting innovative proposals in the general area of extreme-scale hydrodynamics, including, but not limited to, high amplitude wave propagation, very high Reynolds number flows, and abrupt phase changes. Proposed research should investigate innovative theoretical and computational modeling approaches relying on first principles-based closures of the governing laws of fluid motion under such conditions.
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