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Diffractive Solar Sailing

Created: 2026-04-06 (session 35) | Updated: 2026-04-06 (session 37) | Data source: TechPort 117028 + NIAC Phase III 2023 Symposium Poster (fileId 381112) + 183697 live record

Summary

Diffractive Solar Sailing is a NIAC Phase III program (JHU/APL lead, 2022-2024) developing solar sails that use diffraction rather than reflection to generate radiation pressure. The key innovation: diffraction enables a transverse (in-plane) thrust force that reflection cannot produce, allowing novel solar polar orbits without the complex attitude maneuvers required by reflective sails. The target mission is a Solar Polar Orbiter constellation achieving >65° inclination above the ecliptic.

As of the 2023 NIAC Symposium Poster, the team is manufacturing and characterizing physical diffractive grating samples and preparing for radiation pressure testing — TRL 4 lab demonstration territory.

TechPort Records — Complete Lineage

The diffractive sailing concept has a 13-year NIAC history across two institutional homes. All RIT entries list Grover Swartzlander as PI; the Phase III at JHU/APL lists Amber Dubill as PI, with Swartzlander as Co-I — suggesting the program passed to a new lead when the APL team (better positioned for grating fabrication) took charge.

Stage Project ID Lead Org Period TRL Status Key Outcome
Pre-lineage Phase I 4371 Rochester Institute of Technology 2011-2012 1→1 Completed Transitioned_To NSF (551) + ONR (2330)
Phase I 95596 Rochester Institute of Technology 2018-2019 1→2 Completed Advanced_To [96186]
Phase II 96186 Rochester Institute of Technology 2019-2021 3→3 Completed Transitioned_To DARPA (4876) + Industry
Phase III 117028 JHU/APL 2022-2024 3→4 Completed Advanced_From [95596]

6-year gap: [4371] (2011-2012) → [95596] (2018-2019). The early concept attracted NSF and ONR interest immediately, but no follow-on NIAC phase was awarded for 6 years. The program rebooted in 2018 with a fresh Phase I, now explicitly targeting diffractive metamaterial films rather than just the optical lift force concept.

DARPA transition at Phase II: [96186] Transitioned_To DARPA (4876) AND Industry after Phase II completion. DARPA's interest likely reflects applications in directed energy, inertial navigation, or satellite attitude control — not solar polar orbits specifically. An independent Industry transition is also noted (partner unnamed).

Institutional transition at Phase III: Swartzlander (RIT, physicist) generated the concept and ran Phases I and II. Dubill (APL, aerospace engineer) led Phase III at JHU/APL, with Swartzlander as Co-I and Les Johnson (MSFC) joining as Co-I. APL brings grating fabrication capability (MEMS-class clean rooms) and mission systems engineering depth.

Key personnel (Phase III): - PI: Dr. Amber Dubill (JHU/APL), NIAC Fellow - Co-Is: Dr. Grover Swartzlander (RIT), Dr. Les Johnson (NASA MSFC), Dr. Angelos Vourlidas (JHU/APL), Dr. George Ho (JHU/APL), Dr. David Shrekenhamer (JHU/APL)

Technical Concept

Why Diffraction Instead of Reflection?

A reflective solar sail produces radiation pressure normal to the sail surface (pushing the sail away from the sun). To orbit at high solar inclination, you must tilt the sail forward and backward in complex sequences. This requires intricate attitude control and limits achievable orbital inclinations.

A diffractive sail uses gratings to redirect photons, producing a transverse force component — thrust in the plane of the sail. This transverse force is otherwise physically impossible with a reflective sail. Consequence: the sail can be held sun-facing throughout the orbit while still generating the lateral acceleration needed to climb out of the ecliptic plane.

Additional efficiency gains (from Phase II analysis): - Simpler attitude control scheme (no tilting required) - Simpler heat management configuration (constant sun-facing orientation) - Smaller sail for equivalent performance (less risk of boom buckling) - Enhanced acceleration from mass reduction

Material and Fabrication

  • Base material: CP-1 resin (polyimide) — under 10 microns thick
  • Grating layer: Aluminum (~100 nm thick) deposited by evaporation
  • Grating design: Saw-tooth prism geometry, 6 micron pitch
  • Fabrication: Master mold created in silicon wafer (MEMS process); CP-1 spun onto mold, cured, and removed. Aluminum layer added after demolding.
  • Current sample size: 1" × 1", can scale to 6" diameter wafers
  • First-iteration transverse efficiency: ~30%

The grating pitch and profile control the momentum transfer direction and magnitude. Multiple parameters explored: steepness of cut-off, smoothness, rounding, step size, feature resolution.

Optical Characterization Results

  • Testing at two wavelengths: 780 nm and 830 nm
  • Preliminary optical characterization at JHU APL before sending to NASA MSFC's Combined Environmental Effects Facility for space weathering tests
  • Radiation pressure testing using broadband source (RIT torsion oscillator setup)
  • Target: characterize realistic diffractive sail dynamics for inclusion in orbital trajectory models

Mission Architecture: Solar Polar Orbiter Constellation

Mission concept: A constellation of diffractive sails circumnavigating the Sun at >65° inclination above the ecliptic, providing continuous multi-view coverage of the solar poles.

Context: - NASA's Ulysses and ESA's Solar Orbiter are the only two missions to significantly leave the ecliptic — neither achieved polar coverage - Solar poles are critical for heliophysics: originate solar wind, magnetic pole reversals, coronal hole dynamics - Decadal Survey 2024 (Solar and Space Physics) submission made for this concept

Trajectory design: - Trajectory spirals inward toward the Sun from Earth's orbit, gaining velocity from solar radiation pressure - Transitions out of the ecliptic plane at perihelion (high solar flux = peak acceleration) - Target: >65° inclination, >0.5 AU — simultaneous multi-view of solar poles - Flight dynamics solutions exist for both aggressive (1.5 AU perihelion) and conservative (2.9 AU) paths

Alignment with NASA strategic programs: LWS (Living With a Star), Helio 2050

Phase III Status and Roadmap

Current Phase III activities (as of 2023 NIAC Symposium): - Orchestrated workshop with solar sailing community (Dec 2023) - Developed, modeled, and analyzed reflective diffractive active grating design - Explored diffractive grating methods beyond saw-tooth prism: ie metasurfaces, Beam Co unpolarized samples - Performed grating sample fabrication trades (material, resolution, feature size) - Manufactured first set of CP-1/Al samples - Ongoing optical characterization at JHU APL before MSFC space weathering tests - Modifying RIT torsion oscillator for radiation pressure testing with broadband source - Preparing Solar Polar Orbiter Constellation study

Phase III development areas: 1. Improvement in efficiency of gratings for broadband solar spectrum 2. Manufacturing of sail material and scaling to large areas 3. Complete characterization of realistic diffractive sail dynamics 4. Space qualification of diffractive sail materials

15-year technology roadmap (from poster):

Time Milestone
2 years Improvement + Design of Electro-Optic Attitude Control System
5 years Implementation of Angle-Controlled Electro-Optic Attitude Control System
10 years Implementation of Partially Diffractive Sails
15 years Implementation of Full Diffractive Sails

Significance

Physics innovation: Transverse radiation pressure is a genuine physical difference from reflective sails — not an incremental improvement but an enabling capability for specific orbit classes.

Mission enabling: Solar polar orbits are a persistent heliophysics goal (Ulysses only reached ~80° on parabolic trajectories; Solar Orbiter targets 34° at best). A polar-orbiting constellation would be transformative for space weather prediction (3-5 day advance warning for Earth-facing CMEs requires polar vantage point).

Les Johnson (NASA MSFC) co-authorship is significant — Johnson is NASA's solar sailing champion and led the Near-Earth Asteroid Scout and Solar Cruiser programs. His involvement means this has internal NASA institutional support beyond NIAC.

Comparison to SCOPE

SCOPE (GSFC, NIAC Phase II active) also uses solar sail propulsion for a heliophysics/outer-planet mission. Key differences:

Feature Diffractive Solar Sailing SCOPE
Sail type Diffractive grating Reflective (conventional)
Mission target Solar polar orbit Neptune-Triton flyby
Science goal Heliophysics Outer planet science
TRL 4 (Phase III) 2→3 (Phase II active)
Decadal alignment Solar/Space Physics Planetary Science

Open Questions

  • [4371] early-concept NSF + ONR transitions: what did NSF/ONR fund downstream? Did any paper trail emerge? (Outside TechPort scope — web search needed)
  • [96186] DARPA + Industry transitions: which DARPA program (likely DARPA Tactical Technology Office or DARPA DSO)? And which Industry partner? (Outside TechPort scope)
  • Closed TechPort record [117028] has Advanced From only — no follow-on NIAC Phase IV or TDM slot visible. Is there a Phase IV concept?
  • Will this feed into a future Solar Cruiser successor or independent technology demonstration?
  • Scalability: 6 micron pitch gratings on 6" wafers — how does this scale to sail areas of 1000 m²?
  • Les Johnson's involvement: is MSFC considering a small-satellite technology demonstration?
  • [4371] early-concept NSF + ONR transitions: what did NSF/ONR fund downstream? Did any paper trail emerge? (Outside TechPort scope)
  • [96186] DARPA + Industry transitions: which DARPA program? And which Industry partner? (Outside TechPort scope)
  • Closed TechPort record [117028] has Advanced From only — no follow-on NIAC Phase IV or TDM slot visible. Is there a Phase IV concept or Solar Cruiser successor?
  • Scalability: 6 micron pitch gratings on 6" wafers — how does this scale to sail areas of 1000 m²?

Parallel Development Branch: Purdue [183697] (Investigated Session 37)

Project 183697: "Origami-inspired Diffractive Sail for Directed Energy Propulsion" - Program: STRG (not NIAC) - Lead: Purdue University (West Lafayette, IN) - PI (contact email): Kenshiro Oguri (kenshiro.oguri@jpl.nasa.gov — JPL affiliation) - Co-org: Marshall Space Flight Center - Period: 2025-05-01 to 2028-05-31 (3-year STRG grant, active) - TRL: not recorded (typical STRG) - TX: TX01.4.6 Advanced Energetic Propulsion (mismatch: ML predicts TX01.4.1 Solar Sails) - Destinations: Moon, Mars, Others Inside Solar System (also mentions interstellar — Alpha Centauri)

This is NOT a continuation of the Swartzlander/APL lineage. PI is Kenshiro Oguri (JPL), not Swartzlander (RIT) or Dubill (APL). The MSFC co-org suggests Les Johnson or another MSFC connection, maintaining the institutional thread.

Key innovation over the NIAC lineage: "Origami-enabled, 3-D shaped diffractive sails" — foldable 3D structures that: 1. Increase producible thrust beyond flat-sail limits 2. Enable photon recycling (redirected photons absorbed and re-emitted) 3. Provide passive beam-riding attitude stability 4. Enable attitude torque/thrust control via shape transformation 5. Greater maneuver capability across orbit phases

Target: Directed energy propulsion — the TX mismatch reflects this: the concept targets laser-driven propulsion (Breakthrough Starshot concept territory) rather than pure solar-pressure sailing. This is a significant extension of scope beyond the solar polar orbiter concept.

Concept diffusion pattern confirmed: Diffractive sail concept has now spread from one academic group (Swartzlander/RIT, 2011–2021) through NIAC maturation (APL/Dubill, 2022–2024) to a second independent academic group (Oguri/JPL-Purdue, 2025–2028) with architectural innovations. The MSFC thread (Les Johnson) provides institutional continuity across all stages. This is a healthy concept proliferation pattern.

Open thread closed: The Purdue project is NOT the same team as the NIAC lineage — it's a parallel branch that independently advances the concept with new origami structural innovations.