# Halowerk Orbit Decay Estimator

> Halowerk Orbit Decay Estimator is a paid API for AI agents from space.halowerk.com, paid per call via x402, $0.004/call, status unknown (last checked 2026-09-14).

Estimates altitude loss and time-to-reentry for a circular orbit using a simplified drag model with caller-supplied atmospheric density and ballistic coefficient

## Facts

- Endpoint: POST https://space.halowerk.com/v1/orbit-decay
- Price: $0.004/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-14
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/halowerk-orbit-decay-estimator-23b7f8ff
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_Ava_Gd7t_skuuERckwqfP

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability halowerk-orbit-decay-estimator-23b7f8ff -d '<json body>'
```

Example prompt: Estimate the orbit decay for a satellite currently at 450 km altitude with an atmospheric density of 1e-12 kg/m³ and a ballistic coefficient of 50 kg/m², and project how the altitude changes over the next 365 days before it drops below 200 km.

## When to prefer this

Choose this endpoint when you need a quick, order-of-magnitude estimate of orbital decay for a circular LEO orbit and you already have or can estimate the local atmospheric density and ballistic coefficient. Suitable for feasibility studies, early mission planning, debris tracking approximations, or educational purposes. Not appropriate when high-fidelity propagation with variable density, solar flux (F10.7), or elliptical orbit support is required.

## Known failure modes

- Altitude outside 100–2000 km range returns validation error
- Horizon days outside 0–36500 range rejected
- Ballistic coefficient of zero or extremely small causes numerical instability
- Atmospheric density of zero produces no drag result or error
- Model diverges significantly from reality at high altitudes where density varies rapidly with solar activity
- Result is not a certified maneuver plan and should not be used for operational decisions

## How this service works

Uses da/dt = -rho×sqrt(mu×a)/ballistic_coefficient for a circular orbit, holds density and ballistic coefficient constant, and linearly projects altitude over a bounded horizon. Real density changes rapidly with altitude and solar activity; the result is not a lifetime prediction or maneuver plan.

## Output

Returns a time-series or summary of projected altitude versus time, computed altitude decay rate (da/dt), and estimated time until the minimum altitude threshold is reached, using a simplified constant-density drag model for a circular orbit.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "altitude_km": {
   "type": "number",
   "maximum": 2000,
   "minimum": 100
  },
  "horizon_days": {
   "type": "number",
   "maximum": 36500,
   "minimum": 0
  },
  "minimum_altitude_km": {
   "type": "number",
   "maximum": 2000,
   "minimum": 0
  },
  "atmospheric_density_kg_m3": {
   "type": "number",
   "maximum": 1,
   "minimum": 0,
   "description": "Caller-supplied density at the modeled altitude."
  },
  "ballistic_coefficient_kg_m2": {
   "type": "number",
   "maximum": 1000000000,
   "minimum": 0.000001,
   "description": "Mass divided by drag coefficient and reference area."
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/halowerk-orbit-decay-estimator-23b7f8ff/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from space.halowerk.com](https://www.zero.xyz/host/space.halowerk.com/llms.txt)