1.PS

What is the complete PS reverse-sizing memory chain?

MASS → PROPELLANT → VOLUME → PRESSURANT → TANK → MASS BUDGET. Bipropellant: work backwards through RCS then OME; monopropellant: single rocket-equation branch.

Propulsion — what is the overall reverse-sizing memory chain?

MASS → PROPELLANT → VOLUME → PRESSURANT → TANK → MASS BUDGET.

Propulsion bipropellant — what is the crucial reverse order?

Work backwards from the final dry/margined mass through the last RCS burn first, then through the earlier OME burn: M_final ← RCS ← OME. Do not size both burns independently from the same final mass.

Propulsion bipropellant — which propellant is split by O/F?

Split only the OME propellant using O/F=0.80. The RCS uses hydrazine only, so after the OME split add the RCS hydrazine to the total fuel-tank hydrazine load.

Propulsion — what do the source labels mean?

[AKATSUKI] = mission/hardware-specific value from published sources. • [COURSE] = course margin/modeling rule. • [ASSUMPTION] = engineering/homework assumption, not verified as Akatsuki-specific.

g0 — what does this symbol mean, and what is its unit?

Name: standard gravitational acceleration • Unit: m/s² • Value used: 9.80665 m/s² • Status: Physical constant

M_dry — what does this symbol mean, and what is its unit?

Name: spacecraft dry mass before course margin • Unit: kg • Value used: 320 kg • Status: AKATSUKI rounded • Note: source notes published dry mass ≈321 kg

margin_dry — what does this symbol mean, and what is its unit?

Name: system-level dry-mass margin • Unit: – • Value used: 0.20 = 20% • Status: COURSE

M_final — what does this symbol mean, and what is its unit?

Name: mass remaining after propellant is spent, including dry-mass margin • Unit: kg • Value used: 384 kg • Status: Derived from input • Note: M_dry(1+margin_dry)

margin_prop — what does this symbol mean, and what is its unit?

Name: propellant allowance • Unit: – • Value used: 0.055 = 5.5% • Status: COURSE • Note: 3% residual + 2% ullage + 0.5% loading

margin_unusable — what does this symbol mean, and what is its unit?

Name: unusable propellant-volume allowance • Unit: – • Value used: 0.10 = 10% • Status: COURSE

margin_gas_mass — what does this symbol mean, and what is its unit?

Name: pressurant mass margin • Unit: – • Value used: 0.20 = 20% • Status: COURSE

margin_gas_volume — what does this symbol mean, and what is its unit?

Name: pressurant-tank unusable-volume margin • Unit: – • Value used: 0.10 = 10% • Status: COURSE

margin_bladd — what does this symbol mean, and what is its unit?

Name: bladder volume margin • Unit: – • Value used: 0.01 = 1% • Status: COURSE

margin_harness — what does this symbol mean, and what is its unit?

Name: propulsion subsystem harness/system budget margin • Unit: – • Value used: 0.10 = 10% • Status: COURSE

rho_f — what does this symbol mean, and what is its unit?

Name: hydrazine density • Unit: kg/m³ • Value used: 1010 kg/m³ • Status: ASSUMPTION • Note: approximate room-temperature value

rho_ox — what does this symbol mean, and what is its unit?

Name: MON-3 oxidizer density • Unit: kg/m³ • Value used: 1440 kg/m³ • Status: ASSUMPTION • Note: approximate room-temperature value

R_He — what does this symbol mean, and what is its unit?

Name: specific gas constant of helium • Unit: J/(kg·K) • Value used: 2077.3 J/(kg·K) • Status: Physical property

gamma_He — what does this symbol mean, and what is its unit?

Name: helium heat-capacity ratio • Unit: – • Value used: 1.667 • Status: Physical property • Note: used in course pressure-regulated formula

T_tank — what does this symbol mean, and what is its unit?

Name: tank/pressurant temperature • Unit: K • Value used: 293 K • Status: ASSUMPTION

sigma_allow — what does this symbol mean, and what is its unit?

Name: allowable tank material stress • Unit: Pa • Value used: 503 MPa • Status: COURSE/ASSUMPTION • Note: not verified Akatsuki tank material

rho_tank — what does this symbol mean, and what is its unit?

Name: tank structural material density • Unit: kg/m³ • Value used: 2810 kg/m³ • Status: COURSE/ASSUMPTION • Note: not verified Akatsuki tank material

DeltaV_OME — what does this symbol mean, and what is its unit?

Name: OME maneuver delta-V • Unit: m/s • Value used: 1000 m/s • Status: ASSUMPTION

Isp_OME — what does this symbol mean, and what is its unit?

Name: OME specific impulse • Unit: s • Value used: 319 s • Status: AKATSUKI hardware test

DeltaV_RCS — what does this symbol mean, and what is its unit?

Name: RCS maneuver delta-V • Unit: m/s • Value used: 200 m/s • Status: ASSUMPTION

Isp_RCS — what does this symbol mean, and what is its unit?

Name: RCS hydrazine specific impulse • Unit: s • Value used: 230 s • Status: ASSUMPTION

O/F_OME — what does this symbol mean, and what is its unit?

Name: OME oxidizer-to-fuel mass ratio • Unit: – • Value used: 0.80 • Status: AKATSUKI OME test condition

P_prop_reg — what does this symbol mean, and what is its unit?

Name: regulated propellant-tank pressure • Unit: Pa • Value used: 1.40 MPa • Status: Mission-based reverse-sizing value

P_He_i — what does this symbol mean, and what is its unit?

Name: initial helium storage pressure • Unit: Pa • Value used: 22.0 MPa • Status: Mission-based reverse-sizing value

n_OME — what does this symbol mean, and what is its unit?

Name: number of 500-N OME units • Unit: – • Value used: 1 • Status: Configuration count

n_RCS23 — what does this symbol mean, and what is its unit?

Name: number of 23-N RCS thrusters • Unit: – • Value used: 8 • Status: Configuration count

n_RCS3 — what does this symbol mean, and what is its unit?

Name: number of 3-N RCS thrusters • Unit: – • Value used: 4 • Status: Configuration count

m_OME_unit — what does this symbol mean, and what is its unit?

Name: mass of one 500-N OME incl. bracket • Unit: kg • Value used: 3.85 kg • Status: Akatsuki-derived component value

m_RCS23_unit — what does this symbol mean, and what is its unit?

Name: mass of one 23-N RCS unit • Unit: kg • Value used: 0.80 kg • Status: Akatsuki-derived component value

m_RCS3_unit — what does this symbol mean, and what is its unit?

Name: mass of one 3-N RCS unit • Unit: kg • Value used: NaN / not supplied • Status: NOT VERIFIED • Note: The script intentionally leaves this unknown.

MR_RCS — what does this symbol mean, and what is its unit?

Name: RCS mass ratio • Unit: – • Value used: ≈1.092721 • Status: Derived • Note: exp(ΔV_RCS/(Isp_RCS g0))

M_before_RCS — what does this symbol mean, and what is its unit?

Name: mass just before the RCS segment • Unit: kg • Value used: ≈419.605 kg • Status: Derived • Note: M_final MR_RCS

Mprop_RCS_nom — what does this symbol mean, and what is its unit?

Name: nominal RCS hydrazine mass • Unit: kg • Value used: ≈35.605 kg • Status: Derived • Note: M_before_RCS−M_final

MR_OME — what does this symbol mean, and what is its unit?

Name: OME mass ratio • Unit: – • Value used: ≈1.376660 • Status: Derived • Note: exp(ΔV_OME/(Isp_OME g0))

M_before_OME — what does this symbol mean, and what is its unit?

Name: mass before the earlier OME segment • Unit: kg • Value used: ≈577.653 kg • Status: Derived • Note: M_before_RCS MR_OME

Mprop_OME_nom — what does this symbol mean, and what is its unit?

Name: nominal OME bipropellant mass • Unit: kg • Value used: ≈158.048 kg • Status: Derived • Note: M_before_OME−M_before_RCS

Mprop_tot_nom — what does this symbol mean, and what is its unit?

Name: nominal total propellant • Unit: kg • Value used: ≈193.653 kg • Status: Derived • Note: OME+RCS nominal

Mprop_RCS — what does this symbol mean, and what is its unit?

Name: RCS propellant after +5.5% • Unit: kg • Value used: ≈37.563 kg • Status: Derived • Note: nominal×1.055

Mprop_OME — what does this symbol mean, and what is its unit?

Name: OME propellant after +5.5% • Unit: kg • Value used: ≈166.741 kg • Status: Derived • Note: nominal×1.055

Mprop_tot — what does this symbol mean, and what is its unit?

Name: total propellant after +5.5% • Unit: kg • Value used: ≈204.304 kg • Status: Derived • Note: Mprop_RCS+Mprop_OME

Mfu_OME — what does this symbol mean, and what is its unit?

Name: OME hydrazine mass after O/F split • Unit: kg • Value used: ≈92.634 kg • Status: Derived • Note: Mprop_OME/(1+O/F)

Mox_OME — what does this symbol mean, and what is its unit?

Name: OME MON-3 mass after O/F split • Unit: kg • Value used: ≈74.107 kg • Status: Derived • Note: Mprop_OME−Mfu_OME

Mfu_total — what does this symbol mean, and what is its unit?

Name: total hydrazine tank load • Unit: kg • Value used: ≈130.197 kg • Status: Derived • Note: Mfu_OME+Mprop_RCS

Mox_total — what does this symbol mean, and what is its unit?

Name: total oxidizer tank load • Unit: kg • Value used: ≈74.107 kg • Status: Derived • Note: Mox_OME

Vfu — what does this symbol mean, and what is its unit?

Name: hydrazine volume before unusable-volume margin • Unit: m³ • Value used: ≈0.128908 m³ • Status: Derived • Note: Mfu_total/rho_f

Vox — what does this symbol mean, and what is its unit?

Name: MON-3 volume before unusable-volume margin • Unit: m³ • Value used: ≈0.051463 m³ • Status: Derived • Note: Mox_total/rho_ox

Vprop — what does this symbol mean, and what is its unit?

Name: total propellant liquid volume before +10% • Unit: m³ • Value used: ≈0.180371 m³ • Status: Derived • Note: Vfu+Vox

Vfu_m — what does this symbol mean, and what is its unit?

Name: margined fuel-tank propellant volume • Unit: m³ • Value used: ≈0.141799 m³ • Status: Derived • Note: Vfu×1.10

Vox_m — what does this symbol mean, and what is its unit?

Name: margined oxidizer-tank propellant volume • Unit: m³ • Value used: ≈0.056610 m³ • Status: Derived • Note: Vox×1.10

Vprop_m — what does this symbol mean, and what is its unit?

Name: total margined displaced propellant volume • Unit: m³ • Value used: ≈0.198408 m³ • Status: Derived • Note: Vfu_m+Vox_m

M_He_nom — what does this symbol mean, and what is its unit?

Name: nominal pressure-regulated helium mass • Unit: kg • Value used: ≈0.81248 kg • Status: Derived • Note: course regulated-gas equation

M_He — what does this symbol mean, and what is its unit?

Name: helium mass after +20% margin • Unit: kg • Value used: ≈0.97498 kg • Status: Derived • Note: M_He_nom×1.20

V_He — what does this symbol mean, and what is its unit?

Name: helium storage volume at initial high pressure • Unit: m³ • Value used: ≈0.026974 m³ • Status: Derived • Note: M_He R_He T/P_He_i

V_He_m — what does this symbol mean, and what is its unit?

Name: helium tank volume after +10% • Unit: m³ • Value used: ≈0.029671 m³ • Status: Derived • Note: V_He×1.10

r_fu — what does this symbol mean, and what is its unit?

Name: equivalent spherical fuel-tank inner radius • Unit: m • Value used: ≈0.32349 m • Status: Derived • Note: (3Vfu_m/4π)^(1/3)

t_fu — what does this symbol mean, and what is its unit?

Name: fuel-tank shell thickness • Unit: m or mm • Value used: ≈0.450 mm • Status: Derived • Note: P_prop r/(2σ_allow)

M_tank_fu — what does this symbol mean, and what is its unit?

Name: fuel tank shell mass • Unit: kg • Value used: ≈1.666 kg • Status: Derived • Note: rho_tank×shell volume

r_ox — what does this symbol mean, and what is its unit?

Name: equivalent spherical oxidizer-tank inner radius • Unit: m • Value used: ≈0.23820 m • Status: Derived • Note: (3Vox_m/4π)^(1/3)

t_ox — what does this symbol mean, and what is its unit?

Name: oxidizer-tank shell thickness • Unit: m or mm • Value used: ≈0.331 mm • Status: Derived • Note: P_prop r/(2σ_allow)

M_tank_ox — what does this symbol mean, and what is its unit?

Name: oxidizer tank shell mass • Unit: kg • Value used: ≈0.665 kg • Status: Derived • Note: rho_tank×shell volume

r_He — what does this symbol mean, and what is its unit?

Name: equivalent spherical helium-tank inner radius • Unit: m • Value used: ≈0.19205 m • Status: Derived • Note: (3V_He_m/4π)^(1/3)

t_He — what does this symbol mean, and what is its unit?

Name: helium-tank shell thickness • Unit: m or mm • Value used: ≈4.200 mm • Status: Derived • Note: P_He_i r/(2σ_allow)

M_tank_He — what does this symbol mean, and what is its unit?

Name: helium tank shell mass • Unit: kg • Value used: ≈5.590 kg • Status: Derived • Note: rho_tank×shell volume

M_PS_known — what does this symbol mean, and what is its unit?

Name: known bipropellant PS dry-mass subtotal excluding 3-N thrusters • Unit: kg • Value used: ≈19.146 kg • Status: Derived • Note: OME+8×23N+He+3 tanks

mono_full_mission — what does this symbol mean, and what is its unit?

Name: switch for mono delta-V comparison • Unit: boolean • Value used: true • Status: Model option • Note: true gives ΔV_mono=ΔV_OME+ΔV_RCS=1200 m/s

DeltaV_mono — what does this symbol mean, and what is its unit?

Name: hypothetical all-hydrazine mission delta-V • Unit: m/s • Value used: 1200 m/s • Status: Derived input • Note: same total modeled delta-V as biprop case

Isp_mono — what does this symbol mean, and what is its unit?

Name: monopropellant specific impulse • Unit: s • Value used: 230 s • Status: ASSUMPTION

T_RCS23 — what does this symbol mean, and what is its unit?

Name: thruster force class in mono architecture • Unit: N • Value used: 23 N • Status: Hardware class

n_mono — what does this symbol mean, and what is its unit?

Name: number of 23-N thrusters in hypothetical mono model • Unit: – • Value used: 8 • Status: Simplifying assumption

use_akatsuki_pressure — what does this symbol mean, and what is its unit?

Name: blowdown pressure-set selector • Unit: boolean • Value used: true • Status: Model option • Note: uses 1.40 MPa initial tank pressure

P_inlet_min — what does this symbol mean, and what is its unit?

Name: assumed minimum thruster inlet pressure • Unit: Pa • Value used: 0.59 MPa • Status: ASSUMPTION • Note: not verified as an Akatsuki-specific minimum

dP_feed — what does this symbol mean, and what is its unit?

Name: feed-line pressure loss • Unit: Pa • Value used: 35 kPa • Status: COURSE/ASSUMPTION

P_tank_i_mono — what does this symbol mean, and what is its unit?

Name: initial blowdown tank pressure • Unit: Pa • Value used: 1.40 MPa • Status: Akatsuki-based active level • Note: alternative course branch uses 2.76 MPa inlet max + 35 kPa

P_tank_f_mono — what does this symbol mean, and what is its unit?

Name: final blowdown tank pressure • Unit: Pa • Value used: 0.625 MPa • Status: Derived • Note: P_inlet_min+dP_feed

MR_mono — what does this symbol mean, and what is its unit?

Name: monopropellant mass ratio • Unit: – • Value used: ≈1.702378 • Status: Derived • Note: exp(ΔV_mono/(Isp_mono g0))

M_wet_mono — what does this symbol mean, and what is its unit?

Name: wet mass before the modeled mono burn • Unit: kg • Value used: ≈653.713 kg • Status: Derived • Note: M_final MR_mono

Mprop_mono_nom — what does this symbol mean, and what is its unit?

Name: nominal hydrazine mass • Unit: kg • Value used: ≈269.713 kg • Status: Derived • Note: M_wet_mono−M_final

Mprop_mono — what does this symbol mean, and what is its unit?

Name: hydrazine mass after +5.5% allowance • Unit: kg • Value used: ≈284.547 kg • Status: Derived • Note: Mprop_mono_nom×1.055

Vprop_mono — what does this symbol mean, and what is its unit?

Name: hydrazine liquid volume • Unit: m³ • Value used: ≈0.281730 m³ • Status: Derived • Note: Mprop_mono/rho_f

Vprop_mono_m — what does this symbol mean, and what is its unit?

Name: hydrazine volume after +10% unusable allowance • Unit: m³ • Value used: ≈0.309903 m³ • Status: Derived • Note: Vprop_mono×1.10

B — what does this symbol mean, and what is its unit?

Name: blowdown ratio • Unit: – • Value used: 2.24 • Status: Derived • Note: P_tank_i/P_tank_f

Vgas_i — what does this symbol mean, and what is its unit?

Name: initial helium gas volume in blowdown tank • Unit: m³ • Value used: ≈0.249922 m³ • Status: Derived • Note: Vprop_mono_m/(B−1)

M_He_mono_nom — what does this symbol mean, and what is its unit?

Name: nominal helium mass for blowdown • Unit: kg • Value used: ≈0.57486 kg • Status: Derived • Note: P_i Vgas_i/(R_He T_tank)

M_He_mono — what does this symbol mean, and what is its unit?

Name: helium mass after +20% margin • Unit: kg • Value used: ≈0.68984 kg • Status: Derived • Note: nominal×1.20

Vtank_mono — what does this symbol mean, and what is its unit?

Name: total propellant+gas tank internal volume • Unit: m³ • Value used: ≈0.559825 m³ • Status: Derived • Note: Vprop_mono_m+Vgas_i

Vtank_mono_m — what does this symbol mean, and what is its unit?

Name: tank volume after +1% bladder margin • Unit: m³ • Value used: ≈0.565423 m³ • Status: Derived • Note: Vtank_mono×1.01

r_mono — what does this symbol mean, and what is its unit?

Name: radius of cylindrical tank with hemispherical ends • Unit: m • Value used: ≈0.46607 m • Status: Derived • Note: [9V/(16π)]^(1/3) under course geometry assumption

h_cyl — what does this symbol mean, and what is its unit?

Name: length of straight cylindrical section • Unit: m • Value used: ≈0.20714 m • Status: Derived • Note: 4r/9

t_sphere — what does this symbol mean, and what is its unit?

Name: required hemispherical-end thickness • Unit: m or mm • Value used: ≈0.649 mm • Status: Derived • Note: P_i r/(2σ_allow)

t_cyl — what does this symbol mean, and what is its unit?

Name: required cylindrical-wall thickness • Unit: m or mm • Value used: ≈1.297 mm • Status: Derived • Note: P_i r/σ_allow

t_used — what does this symbol mean, and what is its unit?

Name: constant tank thickness selected • Unit: m or mm • Value used: ≈1.297 mm • Status: Derived • Note: max(t_sphere,t_cyl)=t_cyl

M_tank_mono — what does this symbol mean, and what is its unit?

Name: monopropellant tank shell mass • Unit: kg • Value used: ≈12.192 kg • Status: Derived • Note: shell-volume calculation with t_used

M_PS_mono — what does this symbol mean, and what is its unit?

Name: mono PS dry-mass subtotal before harness • Unit: kg • Value used: ≈19.282 kg • Status: Derived • Note: 8×0.80 + M_He_mono + M_tank_mono

M_PS_mono_harness — what does this symbol mean, and what is its unit?

Name: mono PS dry-mass budget after +10% harness • Unit: kg • Value used: ≈21.210 kg • Status: Derived • Note: M_PS_mono×1.10

Propulsion — Step B1: Dry mass margin • What do you do, and what equation is used?

Equation: M_final=M_dry(1+margin_dry) • Purpose: Establish the final mass that remains after all propellant is spent. • With current inputs: M_final=384 kg