Research lead: Biswajit Jana · Engineering model v0.6 · 26 October 2026
The starting question is whether Earth can send a newly chosen message to a receiver 4.24 light-years away and receive an immediate reply. For ordinary propagation through flat spacetime, the first transmission takes approximately 4.24 years and the earliest immediate response takes another 4.24 years (illustrative fixed separation). Higher bit rates do not shorten the propagation time.
The accompanying 12-page PDF and six large SVG design drawings were generated locally and supplied in the v0.6 download package. The PDF and new SVG binaries/figures are not yet uploaded to GitHub; this document reproduces the critical system block diagrams directly using Mermaid, and provides working reference code.
flowchart LR
subgraph E["EARTH STATION"]
E1["Optical Tx: PPM + FEC + telescope"]
E2["Optical Rx: photon count + FEC"]
end
subgraph P["PROXIMA STATION"]
P1["Optical Rx: photon count + FEC"]
P2["Optical Tx: PPM + FEC + telescope"]
end
E1 -- "Forward photons; approx. 4.24 years" --> P1
P2 -- "Reply photons; another approx. 4.24 years" --> E2
This is two-way communication, not an FTL circuit. Even if payload transmission took only milliseconds, the ordinary request-to-reply delay is about 8.48 years before processing overhead.
flowchart LR
DATA["Fresh measurement"] --> CRC["Packet + CRC"]
CRC --> FEC["Error-control encoding"]
FEC --> PPM["FPGA PPM pulse timing"]
PPM --> DRIVER["Qualified laser driver with interlock"]
DRIVER --> LASER["Optical source"]
LASER --> TELESCOPE["Transmitter pupil + fast steering mirror"]
CAM["Beacon / guide camera"] --> CONTROL["Pointing controller"]
CONTROL --> TELESCOPE
SAFETY["Hardware E-stop, power monitoring"] --> DRIVER
The laser source and its driver must be selected and qualified for optical power, pulse energy, timing, eye safety, temperature, interlocks and electrical compatibility. Do not treat a firmware GPIO as a replacement for a certified optical safety interlock.
flowchart LR
SCOPE["Receiving telescope"] --> FILTER["Spectral filter and coupling"]
FILTER --> DETECTOR["Vendor-qualified SPAD or SNSPD"]
DETECTOR --> TDC["Digital event timestamps"]
CLOCK["Reference oscillator; epoch / sync"] --> TDC
TDC --> SLOTS["Slot alignment + count statistics"]
SLOTS --> DECODER["Soft decisions + FEC"]
DECODER --> CRC["CRC / erasure flag"]
CRC --> OUT["Verified reconstructed new data"]
A detector’s bias/quench or cryogenic subsystem is not specified here. Its event output may require correct LVTTL/LVDS compatibility, vendor termination, ESD controls and time-tagging calibration. We have no physically validated advanced detector PCB.
Controller 3.3-V GPIO -> 330-ohm resistor -> visible LED -> ground. Across a short air gap, a phototransistor has its emitter at receiver ground and collector at a sense node pulled up to 3.3 V by 10 kohm. A suitable 3.3-V Schmitt input timestamps the node. Light pulls the node LOW; invert the bit decision.
Approximate TX LED current for an assumed 2.0-V forward voltage: \(I = \frac{3.3\,{\rm V}-2.0\,{\rm V}}{330\,\Omega} \simeq 3.9\,{\rm mA}.\) This is a concept, not a validated circuit board. Confirm GPIO ratings, LED current, phototransistor pinout, rise/fall time, light levels, wiring and all component datasheets before construction. It is not a single-photon receiver.
For an unobscured circular transmitting pupil and a much smaller aperture at the receiver plane of its diffraction pattern, define
\[z=\frac{\pi D_tD_r}{2\lambda R},\qquad \eta_{\rm capture}\simeq \frac{z^2}{4},\qquad N_{\rm detected/s} \simeq \frac{P_t}{hc/\lambda}\,\eta_{\rm capture}\,\eta_{\rm system}.\]This is an ideal small-receiver, far-field approximation, not a full telescope model. The reproducible v0.6 source uses a stable fourth-order correction. At 4.24 ly, 1064 nm, 10 W, $D_t=1$ m, $D_r=10$ m and 20% end-to-end efficiency, it predicts 0.363 detected photons/s in this optimistic idealisation. Real acquisition, jitter, atmospheric and background losses are excluded.
For uncoded M-slot PPM at zero background, if a pulse produces a Poisson mean $s$ and a tie is guessed uniformly when no photon is detected, the symbol error probability is exactly
\[P_{\rm SER}=(1-1/M)e^{-s}.\]A coded radio/optical modem with timing uncertainty and background requires much more than this analytic lower-complexity control. The additional regression tests check parameter rejection, aperture scaling, inverse-square distance, zero-background PPM and one-way/round-trip timing.
Run:
python -m research_tools.interstellar_optical_budget
python -m unittest discover -s research_tools/tests -v
The Krasnikov-tube paper describes a hypothetical spacetime with an unusually short theoretical round trip when a corridor has been established. It is a mathematical geometry, not a buildable receiver or modulator. Such proposals face exotic matter/energy, source, stability, horizon, global causality and chronology constraints. Alcubierre and Lobo’s review is an appropriate starting point.
A proposed experiment requires (i) a physically consistent source of its candidate metric, (ii) a calculation of $J^+(A)$ under the actual metric, (iii) a freshly randomised message $X$ at event A, (iv) receiver-only record Y at event B, (v) measured clock uncertainty and side-channel exclusion, and (vi) replication. The no-signalling theorem rules out encoding a fresh bit into Bob’s local marginal using entanglement alone.
Project status: software-level calculations and conceptual electronics only. There is no demonstrated light-speed-limit violation or constructed spacecraft-grade transmitter/receiver.