How do I install the Rocket Sizing skill?

Run npx skillmds@latest add ashfordeou/rocket-sizing in your terminal (requires Node.js), paste this page's agent-chat prompt into Claude, Cursor, or any MCP-connected agent, or download the SKILL.md file and copy it into your agent's skills directory.

Is Rocket Sizing safe to use?

This skill has not completed SkillMD's automated safety review yet. SkillMD never runs a skill's scripts for you; review the SKILL.md before installing.

Which AI agents work with Rocket Sizing?

This skill is tagged as working with Claude Code, Claude.ai, OpenAI Codex. SKILL.md is an open format, so most agents that read a skills directory can load it too.

Is Rocket Sizing free to use?

Yes. Installing skills from SkillMD is free. This skill is licensed under Apache-2.

Who published Rocket Sizing?

ashfordeOU (@ashfordeou) published this skill. Their other Agent Skills are listed on their SkillMD profile.

Rocket Sizing by ashfordeou — Agent Skill

Name: Rocket Sizing
Author: ashfordeOU

Rocket Sizing

Use when you must size launch-vehicle propulsion with the rocket equation: calculate delta-v from specific impulse and the initial and final masses, derive the mass ratio from a delta-v requirement, compute the propellant mass, and sum the delta-v across the stages of a multistage launch vehicle. Produces the stage delta-v, the mass ratio, and the propellant mass that gate the vehicle sizing. Applies to each stage of the launch vehicle in consistent SI units. Trigger: rocket equation, delta-v, mass ratio, propellant mass, staging, specific impulse.

ashfordeOU ad097da 3 files · 8.3 KB Updated Sep 17, 2026

File contents

Rocket Sizing (propulsion/rocket/rocket-sizing)

Use when the task is launch-vehicle propulsion sizing with the rocket equation: delta-v, mass ratio, propellant mass, and multistage delta-v summation.

Domain quick reference

The ideal rocket equation gives delta-v = g0 * Isp * ln(m0 / mf), with g0 = 9.80665 m/s^2.
Units: specific impulse in seconds, masses in kg, delta-v in m/s.
The mass ratio is m0 / mf; the propellant mass is m0 - mf.
A multistage vehicle sums the delta-v of its stages, each computed with its own stage masses and specific impulse.
ECSS space-systems standards frame the launch-vehicle engineering context.

Workflow

Collect stage specific impulse and the initial and final masses.
Compute stage delta-v with rocket_equation_delta_v.
Derive the mass ratio with mass_ratio_from_delta_v.
Compute the propellant mass with propellant_mass.
Sum the stage delta-v with total_stage_delta_v.

Pitfalls

Confusing mass ratio (m0 / mf) with propellant fraction ((m0 - mf) / m0).
Summing delta-v without recomputing the rocket equation per stage with that stage's own masses.
Using a zero final mass (or mf >= m0), which breaks the logarithm.

Behavior contract (gate 3)

The delta-v, mass ratio, propellant, and staging logic is exercised by the gate 3 contract test: scripts/test_rocket_sizing.py against scripts/rocket_sizing_logic.py (stdlib unittest, offline). Run: python3 scripts/test_rocket_sizing.py

Compliance

Standards referenced, not reproduced: ECSS is a free ESA download (ecss.nl/standards); the rocket equation is common propulsion methodology, summary-only per standards-map.yaml.
compliance: STANDARDS-REF, gated: false.

---name: rocket-sizingdescription: Use when you must size launch-vehicle propulsion with the rocket equation: calculate delta-v from specific impulse and the initial and final masses, derive the mass ratio from a delta-v requirement, compute the propellant mass, and sum the delta-v across the stages of a multistage launch vehicle. Produces the stage delta-v, the mass ratio, and the propellant mass that gate the vehicle sizing. Applies to each stage of the launch vehicle in consistent SI units. Trigger: rocket equation, delta-v, mass ratio, propellant mass, staging, specific impulse.license: Apache-2.0---# Rocket Sizing (propulsion/rocket/rocket-sizing)Use when the task is launch-vehicle propulsion sizing with therocket equation: delta-v, mass ratio, propellant mass, andmultistage delta-v summation.## Domain quick reference- The ideal rocket equation gives delta-v = g0 * Isp * ln(m0 / mf), with g0 = 9.80665 m/s^2.- Units: specific impulse in seconds, masses in kg, delta-v in m/s.- The mass ratio is m0 / mf; the propellant mass is m0 - mf.- A multistage vehicle sums the delta-v of its stages, each computed with its own stage masses and specific impulse.- ECSS space-systems standards frame the launch-vehicle engineering context.## Workflow1. Collect stage specific impulse and the initial and final masses.2. Compute stage delta-v with rocket_equation_delta_v.3. Derive the mass ratio with mass_ratio_from_delta_v.4. Compute the propellant mass with propellant_mass.5. Sum the stage delta-v with total_stage_delta_v.## Pitfalls- Confusing mass ratio (m0 / mf) with propellant fraction ((m0 - mf) / m0).- Summing delta-v without recomputing the rocket equation per stage with that stage's own masses.- Using a zero final mass (or mf >= m0), which breaks the logarithm.## Behavior contract (gate 3)The delta-v, mass ratio, propellant, and staging logic is exercisedby the gate 3 contract test: scripts/test_rocket_sizing.py againstscripts/rocket_sizing_logic.py (stdlib unittest, offline). Run:python3 scripts/test_rocket_sizing.py## Compliance- Standards referenced, not reproduced: ECSS is a free ESA download (ecss.nl/standards); the rocket equation is common propulsion methodology, summary-only per standards-map.yaml.- compliance: STANDARDS-REF, gated: false.

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