ECHO: Expandable Commercially-Enabled

Habitable Orbiter

Commercially Enabled LEO/Mars Habitable Module

Illinois Space Society

University of Illinois at Urbana-Champaign

May 15, 2017

Faculty Advisor: Koki Ho, Ph.D.

Team Lead: Ryan Noe

Rachel Di Bartolomeo, Katherine Carroll, Iaroslav Ekimtcov, Destiny Fawley

Brian Hardy, Guangting Lee, Courtney Leverenz, Richard Mannion, Erik Nord

Benjamin O’Hearn, Joshua Pilat, Brandon Sowinski

Introduction

Looking ahead to decommissioning the International Space Station (ISS), an opening will soon exist for a

next-generation habitat system in the Low Earth Orbit (LEO) sector. With NASA setting its long-term

human exploration goals firmly beyond Earth, this next-generation spacecraft also presents a key

opportunity for expansion of the commercial space market. The University of Illinois team proposes

ECHO, the Expandable Commercially-Enabled Habitable Orbiter. ECHO is a Bigelow B330-derived,

four-crew habitation module designed for rapid LEO deployment and future integration in manned Mars

transfer vehicles by 2030. Incorporating both satellite servicing and artificial gravity capabilities, ECHO

is designed with innovation as its centerpiece. Profitability will be achieved through the program’s

innovative focus on satellite servicing and leasing of research space and crew slots as new means of

income. Once launched in 2022, ECHO will be the first space station built and operated entirely by a

private entity, opening the next chapter in a continued human presence off the surface of the Earth.

Concept of Operations Timeline

A partial timeline of ECHO’s fifteen-year lifespan is provided in Figure 1, incorporating the station’s

development and assembly phases and its early years of operation. Prior to 2022, validation of the ECHO

module and both Satellite Servicers (SatServs) will be completed via ground testing and multiple cadence

missions, including the ongoing Bigelow Expandable Activity Module (BEAM) mission on ISS [1] as

well as a test flight of an independent B330 module in 2020. The current BEAM mission will test and

justify the utilization of an inflatable module in an atmosphere practically identical to that of ECHO. The

B330 module being launched in 2020 will be used to justify the technology readiness level of the

inflatable module in LEO. The Shuttle-derived Remote Manipulator System (RMS) as well as docking

points will be evaluated in LEO during cadence missions. High technology readiness levels will be

ensured prior to ECHO becoming fully operational. Completed station components will then launch from

2022 onward, beginning with ECHO itself onboard a Delta IV Heavy (DIV-H) which satisfies the

module’s 27,129 kg mass and 4.6 m payload fairing requirements. [2] Two International Standard

Payload Racks (ISPRs) along with a small portion of consumables and water will be aboard the initial

DIV-H launch, as well.

Falcons will escort four-member crew rotations every six months while Atlas V 401 will launch on nine-

month cycles for resupply including consumables, water, repair equipment, and experimental research

equipment. Three-year refueling missions continuing throughout habitation will occur in addition to a

single Falcon containing the remaining internal and external research racks. A Cygnus-derived refueling

craft will be manufactured for ECHO refueling. Onboard research capability will become fully

operational mid-2023. Launch operations required for ECHO assembly are outlined in Table 1. The RMS

is attached to ECHO prior to being launched, and therefore no assembly will be required for this

particular component. In addition to assembly, testing and manipulation of both EERs and docking points

must be completed prior to the ECHO achieving the status of fully functioning.

Figure 1: ECHO and SatServ timeline

Following completion of the main station, satellite servicing via ECHO will begin in late 2023. Satellite

Servicer-1 (SatServ-1) will be launched, via a Falcon, to validate the autonomous servicing architecture.

Practicing fuel transfers to/from ECHO and confirming that docking procedures operate as expected will

be completed over the course of numerous tests onboard ECHO. Final validation of the system will take

place in mid-2024, as SatServ-1 conducts its first test missions to nearby LEO satellite networks. These

tests will entail possible battery or other component replacements, refueling, or minor repairs. After these

early demonstrations, SatServ-1 and SatServ-2 will then begin regularly-scheduled contract missions to

geostationary (GEO) orbits, continuing for over a decade until ECHO is decommissioned in 2037. Due to

the fuel used on the SatServs, these GEO missions have the potential of taking long periods of time.

Therefore, having two will be far more efficient in performing repairs to multiple satellites. A full launch

schedule for ECHO assembly is outlined in Table 1, including masses for resupplies as well as

miscellaneous items such as Orbital Replacement Units (ORUs).

Table 1: ECHO Launch Schedule

ECHO Launch & Assembly Schedule, Beginning January 2022

Launch Vehicle

[1] [2] [3]

First

Launch

Date

Cycle

(Month) Purpose

Consumables

(kg)

Water

(kg)

Misc.

(kg)

Delta IV-Heavy Jan. ‘22 1-Time ECHO + 2 ISPRs 500 2000 1600

Falcon + Dragon2 Feb. ‘22 1-Time Initial 4 Crew 50 50 0

Atlas V 401+ EnhCyg Mar. ‘22 1-Time Initial Resupply 2500 200 800

Falcon + Dragon2 Jul. ‘22 6 4 Crew 50 50 0

Atlas V 401+ EnhCyg Nov. ‘22 9 Resupply 2150 350 1000

Falcon + Dragon Mar. ‘23 1-Time 4 ISPRs + 2 EERs

4ISPR+Research

0 0 3310

Falcon + Dragon Apr. ‘23 1-Time 2 ISPRs + 2 EERs 0 1000 2310

Falcon 9 Dec. ‘23 1-Time SatServ-1 0 0 0

Atlas V 401 + Cygnus Dec. ‘24 36 Fuel Resupply 0 0 0

Falcon 9 Dec. ‘25 1-Time SatServ-2 0 0 0

Commercial Operations

Table 2: Number of Crew Members Owned by NASA over 15 Year Life Span of ECHO

NASA Crew Ownership on ECHO

Year in Operation 1 2-5 6-9 10-15

Crew Members 4 3 2 1

ECHO is designed with profitability in mind, incorporating a variety of attractive features that can

generate lucrative contracts from commercial customers. Initial development is intended to operate much

like the Commercial Crew program, with NASA investing significant funding up front to a private entity

that assumes responsibility for construction and ownership of the ECHO module. [4] In exchange NASA

will receive a certain degree of complimentary crew slots, decreasing over time, with remaining station

space gradually being filled by paying commercial scientists or tourists. This depletion is easily depicted

in Table 2. Other leasable features include the four EERs, acting as both an exterior research platform and

a CubeSat deployment area, as well as the eight flexible-use ISPRs and 45 m3 of multi-use space. By

renting out areas of ECHO and crew slots for commercial operators, a private developer could generate

income from companies involved in Earth imaging, small satellite deployment, micro-gravity

experiments, or prototype habitats that require human monitoring. Finally, the dual SatServ system

provides an enormous amount of profit potential by offering servicing and refueling for both LEO and

GEO satellites.

Applications for Mars Transit During the commercial operations phase, validation and testing for the ECHO-Mars Variant (ECHO-MV)

will commence. This will entail in-orbit research on radiation shielding as well as health effects in micro-

gravity, with actual construction of the ECHO-MV taking place throughout the mid-2020s. A further

explanation of specific system modifications for the Mars Variant can be found in the Adaptations for

ECHO-Mars Variant (ECHO-MV) section. In accordance with concepts outlined in the Mars Architecture

Overview, an SLS Block 1B will launch the 37,761 kg ECHO-MV module to a cis-lunar orbit for vehicle

aggregation between 2028 and 2032. Aggregation will include the chemical or hybrid propulsion system

and Co-manifest Logistics module, with assembly occurring prior to first crew arrival. In 2033, Crew 1

will be launched to the ECHO-MV to begin the 500 day mission to Phobos. [5] Upon returning, ECHO-

MV will be resupplied in cis-lunar space between 2034 and 2039. The propulsion system will be

replaced/resupplied, depending on propulsion type, and consumables/orbital replacement units (ORUs)

will be replenished via a new Co-manifest Logistics Module. Crew 2 will then reuse ECHO-MV for the

culmination of the program; a 1,100 day mission to Mars in 2039. [5] Since the Mars mission architecture

is still under development, ECHO-MV has been designed with the versatility to adapt to changing

architecture. The biggest example of this is ECHO-MV’s optional application of artificial gravity with

certain propulsion systems, shown in Figure 2. If the chemical propulsion system is selected, a tether and

counterweight system can be implemented with modification to provide the crew a Mars equivalent

0.38g, during transit to and from Mars. This system is not practical for the SEP/hybrid propulsion system

due to the extended acceleration time preventing use of a simple tether/cable system. Further details are

explained in the Artificial Gravity section.

Figure 2: ECHO-MV with Orion & Logistics Module (1), Artificial Gravity Option (2), and Hybrid Option (3)

Echo Subsystems

Habitat Layout

In an effort to enable a variety of commercial operations while providing the capability for expansion,

ECHO’s B330 core structure has been modified to include a wide diameter transfer tunnel, four docking

mechanisms and several external hardpoints as shown in Figure 3. The wide transfer tunnel, coupled with

the nadir-facing Common Berthing Mechanism (CBM), allows the transport of equipment up to 1.27 m

diameter into the habitat. Additionally, both ends of the habitat are equipped with a NASA Docking

System (NDS) port to enable seamless crew rotation and a means of emergency egress. A Quest-derived

airlock is integrated with the rearward NDS port, consisting of a crew-lock portion, dedicated gas tanks

for environment regulation, and an EVA hatch located tangent to the core axis. [6] [7] The nadir CBM on

the forward end of the spacecraft provides docking capability for Cygnus, Dragon, and future commercial

expansion modules. The EERs are located on the zenith face opposite the CBM. Adjacent to the CBM on

the port side is the SatServ Berthing Mechanism (SSBM) which provides an isolated refueling point for

SatServ units and Cygnus-derived ECHO refueling craft. Adjacent to the CBM on the starboard side is

the RMS and propellant storage system for ECHO station keeping propellant, SatServ Krypton, and

satellite ADCS replenishment hydrazine. By segregating the fuel transfer and storage system from crew

access points, the risk of hydrazine exposure will be minimized. The centralized location of the robotic

arm also allows for Cygnus docking, EER manipulation, and, if needed, remote fuel storage maintenance.

The ECHO habitat core structure deviates from traditional Bigelow designs with the inclusion of the

Figure 3: ECHO-LEO utilizes four docking points for efficient operations involving crew, cargo, fueling, and

SatServ needs

transfer tunnel and nadir CBM. To ensure these modifications would not compromise structural integrity,

the core structure underwent Finite Element Analysis (FEA) with a 6g axial loading as would be seen

during launch on a DIV-H. [8] Additional loading from attached components (expandable habitat

material, solar arrays, radiators, etc.) were included to improve quality as can be seen in Figure 4. As

expected, maximum loading occurred near the CBM tunnel with peak compression of ~180MPa.

Aluminum 6061 Yield Strength is ~280MPa which leaves a safety factor of only 1.55, less than the

desired safety factor of 2. [9] Further revision to the core structure could be done to reinforce the core

and minimize loading along the CBM port.

Figure 4: Maximum stresses applied to ECHO core structure during Delta IV Launch with 6g acceleration

Crew Accommodations

The habitable volume of ECHO, shown in Figure 5, is divided into three distinct portions to provide

separation between crew quarters and work areas. Dividers provide visual and audio isolation for crew

members and are designed with the same materials used in the B330 exterior walls, consisting of a foam

layer sandwiched between two sheets of Vectran. [10] Each section’s volume was designed in compliance

with the Human Integration Design Handbook’s habitable volume recommendations to provide a safe and

comfortable environment for NASA and commercial astronauts. [11] In total, ECHO has 65 m3 of storage

and 191 m3 of habitable volume.

ECHO’s living arrangements are designed to support a crew of four. The crew quarters are located in the

central section along the rim of the module with 4 m3 of living space for each crew member. While the

NASA Human Integration Design Handbook does not provide a set requirement of living volume, ECHO

provides over twice as much living space as the ISS and Skylab. [11] Near the core and along the rim in

the central section lies the equipment for meal preparation, including the consumables storage and food

preparation area. On the rim across from the consumables storage area of the central section is the general

storage that has a total volume of 10 m3 to be shared among the astronauts. The lower section of ECHO

contains the exercise and hygiene area with a volume of 15 m3 and 10 m3, respectively. Four Category A

windows that are 0.5 m in diameter are built in the module, with two in the upper section and two in the

lower section. Each window will have handholds to facilitate viewing and be equipped with internal

protective panes and covers in accordance with the Human Integration Design Handbook. [11]

Figure 5: Estimated ECHO habitat volume broken down by section and classification

Environmental Control & Life Support System (ECLSS)

ECHO’s consumable requirements include 1.83 kg of food and 8.4 kg of water per person per day, with

an ISS-derived water reclamation system capable of 93% water recovery. Factoring in consumption and a

30% safety margin, ECHO will require 3,476 kg of food and 1,116 kg of water annually. [11] ECHO’s

environmental control systems are based off those currently used on the ISS. The temperature and

humidity control system is comprised of ventilation fans, a cooled hydrophilic-coated condensing heat

exchanger, and a rotary liquid separator to remove condensation from the air stream. Atmospheric control

will consist of the Carbon Dioxide Removal, Trace Contaminant Control, Major Constituent Analyzer

and the Oxygen Generation Assembly. [12] The Carbon Dioxide Removal System contains a 4-bed

molecular sieve which includes Zeolite to assist with CO2 removal and a combination of zeolite and silica

gel to desiccate the incoming air. The Trace Contaminant System is constructed with an activated

charcoal adsorption bed and thermal catalytic oxidizer with post-sorbent bed. The Major Constituent

Analyzer uses mass spectrometry to detect and analyze the atmosphere on the ISS. Lastly, the Oxygen

Generation Assembly utilizes electrolysis to separate hydrogen and oxygen from water molecules to

provide oxygen for the crew on board.

Temperature Control and Environmental Control are based off systems currently used on the ISS. The

Temperature and Humidity Control is comprised of ventilation fans, cooled hydrophilic-coated

condensing heat exchanger and rotary liquid separator to remove condensate from the air stream. The Fire

Suppression system on the ISS consists of distributed smoke detection and portable CO2 fire suppression

bottles. Each crew member is provided a bunk that has a volume of 3 m3 which follows the recommended

sizes for crew accommodations. [13]

Astronauts typically lose 1.5% of bone and muscle mass after six months in microgravity with ISS level

exercise regimens. [14] To counter losing bone and muscle mass, a rigorous 2-3 hour daily exercise

session and vitamin supplements will be implemented for the crew. Each crew member will have their

own exercise routine that will include running on the COLBERT treadmill, cycling on a stationary bike,

and lifting weights using the Advanced Resistive Exercise Device (ARED). [15] [16]

Guidance, Navigation, and Control (GN&C)

ECHO will be placed into an orbit similar to that of the ISS at an altitude of 400 km and 28 inclination.

The ISS’s 51.6° inclination was unnecessary for ECHO since no Russian launch vehicles are required and

28° was selected to maximize payloads on launches from Kennedy Space Center. A 400 km altitude does

result in significant drag effects on ECHO due to its proximity to Earth’s atmosphere. Specifically,

ECHO’s orbit will decrease by 2 km for every month uncorrected. To compensate for this decrease,

ECHO’s bipropellant hydrazine thrusters (with a specific impulse of 235 seconds) will need to impart a

V on the decreased orbit. The estimated specific impulse is based on SpaceX’s SuperDraco engines and

was calculated using the exhaust velocity on page 12 of the Blue Ridge Research and Consulting report.

[17] The V, calculated as a Hohmann transfer from a 398 km to 400 km altitude orbit, is 1.13 m/s per

month. Using the Tsiolkovsky Rocket Equation with a 30% safety margin, the monthly fuel consumption

based on the V is 23.79 kg. [18] The dual-propellant nitrogen tetroxide/monomethyl hydrazine

(NTO/MMH) fuel required for such maneuvers will be stored in an isolated exterior compartment on the

forward, starboard side of the core section near the RSM. This compartment will accommodate 1,500 kg

of attitude, determination, and control systems (ADCS) Dual-Propellant and 2,000 kg of stored Krypton

and hydrazine for SatServ.

While in LEO, ECHO’s orientation will be determined using a combination of absolute attitude sensors

including star, sun, and earth horizon trackers as well as relative attitude sensors including

accelerometers. Surrey Satellite Technology Ltd. (SSTL) manufactures a star, sun, and horizon tracker

that will be implemented onboard the module. The Rigel-L star tracker has a double camera head unit

(CHU) for redundancy and will dissipate approximately 8 W of power while operating. [19] A 2-Axis

DMC Sun Sensor with a maximum power dissipation estimate of 100 mW while in direct sunlight will

also double as a temperature sensing mechanism. [20] The horizon tracker sensor/processor system,

designed by the Servo Corporation, will dissipate 1 W of power. [21] Determination of relative attitude as

well as v will be done by a Multi-Axis Accelerometer Package manufacture by Applied Technology

Associates and dissipates less than 4 W of power during operation. [22]

Once ECHO’s orientation is determined, control moment gyroscopes (CMGs) together with the module’s

thrusters will be responsible for attitude control. ECHO’s maximum moment of inertia is 960,000 kg-m2

and was calculated using Creo Parametric 3.0. An approximate angular acceleration was determined using

maximum output torque and moments of inertia of similarly-sized spacecraft. That angular acceleration,

on the order of 10-5 rad/s, together with the moment of inertia corresponds to 10 N-m of torque in each

direction. Implemented onboard ECHO will be four CMGs (one included for redundancy) each outputting

a maximum torque of 10 N-m. Based on numbers from existing CMGs and scaling for ECHO’s required

torque, the power consumption during spin-up (full power) should be 20 W for each CMG. [23] ECHO-

MV will sport the same GN&C and ADCS components as ECHO’s LEO variant excluding the horizon

tracker, which is unnecessary for interplanetary journeys.

Communications

ECHO’s onboard communications will use the Tracking and Data Relay Satellite System (TDRSS) to

relay a Ku band link of 50 Mbps, which is comparable to data rates for ISS communications. [24] This

network will allow for video, voice, and payload data communication with Earth. ECHO will utilize a

non-parabolic 6 dB gain antenna transmitting over the 12 GHz Ku band frequency, requiring

approximately 5 W of power. [24] Collectively, the system will have a 10 dB link with a margin of 3.6

dB. To ensure redundancy, ECHO will also be equipped with a low data rate S band system.

Thermal Management

The active thermal control system (ATCS) maintains a constant temperature in the ECHO module by

rejecting heat from onboard electronics into space via a network of coolant loops and external radiators.

[25] A thermal simulation was completed using Siemens NX 10.0 to determine the heating from solar,

Earth infrared, and Earth albedo radiation that would need to be dissipated per orbit. The solar flux at the

warmest time of day is shown in Figure 6, with a maximum flux of 1.376 x 10-3 W/mm2. Using an

integration of the total flux over the surface, the maximum power to be rejected, including the amount

generated by the module, was determined to be 8.1 kW per orbit. [26] To satisfy the ATCS heat

dissipation requirements, the module will utilize two radiator wings with a total surface area of 49.5 m2.

The passive thermal control system (PTCS) maintains a safe temperature range for onboard equipment

using a combination of insulating material and surface coatings. ECHO’s insulation consists of alternating

layers of Nextel and protective foam that make up the outside layer of the inflatable shell. To protect the

radiator and solar panel orbital replacement units (ORU) on the exterior of the module, a finished coating

will be applied that provides insulation and radiation protection.

Figure 6: Solar flux due to sun on ECHO. The largest flux occurs on surfaces facing the sun with gradual decrease to

surfaces away from the sun

Power

ECHO will utilize Spectrolab XTJ Prime Triple Junction Solar Cells and Saft VL48E Li-Ion batteries to

provide power during daylight and eclipse periods, respectively. The power requirement for subsystems

of ECHO is calculated in to be 18.88 kW, generating a total power requirement of 40.8 kW. [27] The

solar cells have an end-of-life (EOL) efficiency of 26.7%, so 140 m2 are necessary for a 20% power

contingency battery recharge capability in the 56.5-minute day period. [28] The solar cells have an

expected lifespan of 15 years, so they are not expected to require replacement during the life of the

module.

The Li-Ion batteries are expected to have 100,000 charge/discharge cycles in the 20 year lifespan with an

end of life (EOL) depth of discharge (DOD) of 20%. [29] With an EOL energy density of 105 Wh/kg and

mass of 195 kg, the available EOL energy for each battery is 4390 Wh. For an eclipse period of 36.1

minutes at a 400 km orbit, four batteries will be required to provide the required 12,400 Wh. [30]

Satellite Servicing

The on-orbit servicing capabilities of ECHO’s dual SatServ units have the potential to provide a major

income source for the station while also greatly advancing the GEO satellite market. A single SatServ unit

is pictured in Figure 9, including a breakdown of major components onboard each spacecraft. Each

SatServ is equipped with two robotic arms, used for attaching fuel lines to satellites and manipulating

replacement components during repairs. Also included are autonomous computer systems that will allow

servicing work to occur with minimal human intervention. For propulsion purposes, the craft makes use

of a solar electric propulsion engine to facilitate efficient travel between ECHO and satellites. Accounting

for a journey of approximately six months between ECHO and GEO, calculations indicate that SatServ

has the capability to service up to four satellites per trip to GEO before returning to ECHO to refuel.

Figure 7: DeltaV Contour for various target orbits (left) and propellant mass (right) for SEP maneuvers of SatServ

Figure 7 demonstrates the required delta V and mass of propellant to transfer one SatServ into various

target orbits from ECHO’s orbit. SatServ utilizes electric propulsion with a thruster that has a specific

impulse of 2700 s. The maximum propellant mass for an orbit transfer form LEO to GEO is 154 kg to

provide a delta V of 9.7 km/s. [31] [32] The maximum time required for an orbit transfer was calculated

to be 16 days with a mass flow rate of 2*10-4 kg/s. [31] Figure 8 shows how the operating parameters vary

for the design variations investigated and how the final architecture was chosen. The total propellant

mass was calculated to be around 450 kg, allowing a round-trip orbit transfer and servicing of several

satellites. Krypton was chosen as the propellant due to its similar performance to Xenon for a drastically

reduced price. The required power to accelerate the krypton propellant is approximately 2.5 kW. The

total solar array and propellant cost are $1.33 Million 2017 U.S. dollars. [33]

Figure 8: SEP properties for several propellants as functions of specific impulse. The optimal operating parameters

occur at an Isp of ~2700 seconds

Maintenance services offered by SatServ will include battery replacement, electronics upgrades, and

hydrazine refueling. Utilizing two SatServs maximizes efficiency by having one provide service while the

other travels or refuels at ECHO. Factoring in the fuel needs of both SatServs, as well as the 400 kg/year

fuel requirement of ECHO itself, the station will require refueling every 3 years.

Figure 9: Overview of SatServ Components, power draw and mass

Table 3: ECHO equipment mass, power budget and Technical Readiness Level review for the LEO Variant

ECHO Launch Mass

Ma

ss

(kg

)

Po

wer

(kW

)

TR

L Continued Launch Mass

Ma

ss

(kg

)

Po

wer

(kW

)

TR

L

Payload Thermal [34]

(1) RMS [35] 500 0.55 8

-

9

(2) Radiator Assemblies 750 0 9

(2) ISPRs 1,600 2.0 9 Passive Thermal Con. System 50 0 9

ECLSS Active Thermal Con. System [25] 800 0.55 9

Air Revitalization [12] 447 2.6 9 Power

Temp/Humidity Control [12] 137 2.2 9 (2) XTJ Prime Solar Arrays 200 0 9

Radiation Shielding [36]

http://rascal.nianet.org/wp-

content/uploads/2015/07/MIT_2

016-RASC-AL-Technical-

Report.pdf

2,478

.

0 9 (4) VL48E Li-Ion Batteries 458 0 9

Fire Detect./Suppression [12] 17 0.02 9 Propulsion

Crew Cabin 260 0 9 Bipropellant Hydrazine Thrusters 100 0 9

Water Recovery [13] 734 0.5 9 Propellant Storage System 200 0 9

(1) Treadmill [16] 998 0 9 Fluids

(1) Exercise Bike [16] 250 0 9 ECHO Dual Fuel (MMH/NTO) 1,500 0 9

(1) ARED Device [15] 1,000 0 9 SatServ Propellant Storage 500 0 9

Structures

Water/Ammonia Coolant [25] 300 0 9

Central Structure 5,000 0 7 Potable Water [37] 1,116 0 9

Expandable Exterior 4,000 0 7 Launch Totals 27,129 10.88

(2) NDS Mechanism+CBM [38] 1,250 0.50 7 Additional Equipment (Launched Separate)

EVA Airlock/Gas Storage 3,000 0.25 9 (6) ISPRs 4,800 6 9

Attitude Det. & Control Food (Annual,1.83 kg/day/person) 3,476 0 9

(4) CMG [23] 32 0.08 9 Water (Annual) 1,116 0 9

(2) Star Tracker [19] 4.4 0.016 9 (4) EERs 1,600 2 9

(2) Sun Sensor [20] 0.42 0.0002 9 (4) EVA Suits 240 0 9

(2) Accelerometer [22] 2.6 0.008 9 Repair Tools and ORUs 1,000 0

Horizon Tracker [21] 1.5 0.001 9 Equipped Orbiting Total 39,361 18.88

Communications/Data Handling

(2) Antenna (Ku) and Radio [39] 207 0.1 9 Orbiting Total + 15% Margin 43,297 20.77

(1) Non-Par. 6 dB Gain Antenna 200 0.1 9

Data Bus Architecture 100 0.5 9

Adaptations for ECHO-Mars Variant (ECHO-MV) ECHO has been designed as a two-purpose vehicle. After it has been demonstrated as a successful LEO

module, work will commence to modify its systems to accommodate an interplanetary journey. Given the

lack of access to the ground and the more intense radiation and thermal effects outside of Earth’s sphere

of influence, some systems, like ECLSS, will need to be more heavily modified than others. Following

updates, the vehicle will be prepared for a four-person crewed journey to Phobos and Mars.

Power

ECHO will require an upgraded power system for a Mars mission. With the 21.55 kW power requirement

calculated in Table 2, the solar array area with a 20% contingency will be 232 m2. According to NASA’s

2015 Technology Roadmap, advanced lithium batteries will be developed by 2021 and can be used for

future Mars missions. The batteries are expected to provide an EOL energy density of 175 Wh/kg with a

30% DOD, so 771 kg of battery mass will be utilized on a Mars transit mission. [40]

Communications

The communication system on the transit to Mars will utilize a 1 kW radio in order to transmit data to a

34-meter DSN antenna from a maximum distance of 2.5 AU at a 10 Mbps data rate. [41] [42] This will be

accomplished using an 8.45 GHz X-band frequency with a 3.8 m parabolic antenna, which will provide a

13 dB link with a 3 dB margin. [43]

Upgraded ECLSS Components

ECHO-MV will be equipped with largely similar ECLSS components and exercise devices that are on

board ECHO; however, certain ECLSS components will be upgraded. [12] The carbon dioxide reduction

and removal, temperature and humidity control, trace contaminant, waste management and water

processing systems need to be modified and adapted for ECHO-MV. A high pressure oxygen generator

assembly will be used to allow switching between cabin air composite and re-pressurizing the oxygen

tanks. Nitrox will be used instead of pure nitrogen for the pressurized gas management as it provides a

safer direct feed for the crew members. ECLSS components that are currently being developed for deep

space travel include the fire detection and suppression system, cascade water distillation system and brine

processing system.

For systems that are vital to the survival of the crew, additional consideration was taken into account in

the event of a system failure. There will be sufficient oxygen and water supplies on board for the crew to

survive for several days in the event the oxygen generation or water recycling systems require repair.

There will be two units of carbon dioxide reduction and removal systems as well as temperature and

humidity control systems on board the vehicle. This fully redundant design was selected as this will be

enough time to repair the subsystems should they fail. With the upgraded systems and additional

redundancies, a failure of a subsystem will not cripple the mission and will allow the crew to mitigate the

situation.

Consumables and Crew Health

Each crew member will require 1.83 kg of food and 8.4 kg of water per day, bringing a total of 8,056 kg

of food and 36,960 kg of water required for the full 1,100 day mission. [13] However, the water recovery

system is able to recycle 93% of the water; hence, ECHO will only require 2,587 kg of water. [37] When

a 30% safety margin was included, the total amount of food and water that is needed would be 10,473 kg

and 3,363 kg, respectively. Similar to ECHO, the Mars transit vehicle will be equipped with the ARED

weight device, a COLBERT treadmill, and an exercise bike. Although the Mars transit vehicle may be

equipped with artificial gravity, the gravity experienced by the crew will be less than that on Earth.

Therefore, in order to retain muscle and bone mass throughout the mission, the crew will have similar

exercise schedules compared to those on ECHO.

Risk Mitigation

Four systems that were vital for human life was taken into account when considering the redundancies the

Mars transit vehicle needed to be equipped with due to its long duration spent isolated in space. The four

systems were those that generated oxygen, carbon dioxide, humidity and water. [11] When determining if

a backup system was needed, the time from which a failure occurs till the time where the living

conditions deteriorate to critical level was taken into account. For the oxygen and water systems, the time

taken for the environment to reach critical levels would be three days respectively, therefore a backup

system will not be necessary. The carbon dioxide and humidity systems will take 20.5 hours and between

1 to 10 hours for the environment to reach critical levels. [12] For these two systems, the amount of time

required to restore the system is under a day; therefore, a backup system is required. Thermal control

would also require a backup as the electronics could overheat in a short period of time. Because the fire

detection sensors are distributed around the cabin, they will provide a backup for each other should one

sensor fail and thus additional redundancy would not be required. The waste processing system would not

require a redundancy as there would be sufficient time for the system to be repaired.

In terms of maintaining and repairing, the systems should be designed to allow common parts to be used

on the subsystems. This would allow less parts that would have to be brought on board the Mars transit

vehicle and also less training of the crew members would be required. 3D printing could also be used to

manufacture the spare parts in space which would reduce the amount of ORUs needed to be brought on

board and allows for the flexibility to make different parts on demand. The systems with redundancies

will be repaired while the backup system is running and the repaired system will then be used as a

redundancy once it is back in working condition.

The long durations of the trip to Mars can prove to have a substantial effect on the crew members. In

addition to the effects of radiation and microgravity, the crew will also have to endure a long period with

three other crew members. [44] The potential effects of living in an isolated environment may include

motivational decline, fatigue, and strained crew relations. There will be a plan that will be used to de-

escalate the situation should a significant conflict occur. In order to counter any psychological factors that

the crew will face, psychological condition should be taken into account during crew selection and the

crew should undergo psychological training and be provided with in-flight support.

Radiation

In the transit to Mars, ECHO will be exposed to cosmic rays without the protection of the Earth’s

magnetic field. It will require significant shielding for radiation levels to remain low enough for

habitation. According to Bigelow, the B330 exterior wall provides the equivalent shielding as 27 g/cm2

aluminum specifically for deep space habitation. [36] Along with the protection normally provided by the

B330 shell, the exterior walls of the ECHO-MV will be coated with polyethylene for the Mars Transit as

Polyethylene is one of the most effective shielding materials [45]. The walls of the Mars Transit Vehicle

(MTV) will have a layer of 10 g/cm2 polyethylene. With a surface area of 91.79 m2, this additional mass

is 917.90 kg, In addition, two of the crew quarter walls (44.4 m2) will be lined with another 10 g/cm2 of

polyethylene which will be utilized in the event of a solar particle event bringing mass for ECHO MV to

1,361.9 kg .The density of the polyethylene chosen is based on the fact that research has shown that for a

two-layer shielding system with 10 g/cm2 aluminum and 10 g/cm2 polyethylene, only 0.26 Gray-

Equivalent (Gy-Eq) of radiation will pass through the shielding. [46] Having robust radiation protection

on the vehicle will ensure that the crew will adhere to the short-term dose limits provided by NASA of 1.5

Gy-Eq for eyes, 3.0 Gy-Eq for skin and 0.5 Gy-Eq for blood forming organs. [47] [48]

Artificial Gravity Options

Based on the current Mars Architecture Technology Overview, ECHO-MV will have the option of

including an artificial gravity system. The purpose of creating artificial gravity is to mitigate the harmful

effects of lengthened zero-g exposure on the crew. For this adaptation, the crew capsule will be tethered

to the SLS Block 1B Exploration Upper Stage, which will act as a 12,800 kg counterweight. [49] The

MTV will be the center of the rotating system and will contain a hub portion to attach the crew capsule

and counterweight. In order to ensure that the artificial gravity system offers a practical advantage over

weightlessness without requiring a large amount of propellant and structural mass to produce 1 g, the

rotating tethered body will create a nominal artificial gravity of 0.38 g to simulate the gravitational

strength on the Martian surface. Another optional capability of ECHO-MV will be incorporating a hybrid

architecture of solar electric propulsion (SEP), as shown at right in Figure 10 below.

Figure 10: ECHO-MV with chemical propulsion and artificial gravity configuration (left) and SEP Hybrid

Architecture (right) *Cable lengths are NOT to scale.

The artificial gravity system will be attached to either side of the MTV hub using a set of six evenly

spaced Kevlar cables. The crew capsule and counterweight will be connected to the hub by cables that are

37.76 m and 88.49 m long, respectively. Six sets of these cable pairs are required for a total mass of 24.76

kg. [50] The cables are attached using Bloom Series 8000 winches, which have a pulling capacity of up to

289,000 N. [51] Since the rotation requires a centripetal force of 112,000 N, these winches overcome the

maximum centripetal force exerted by the station with a safety factor of 2.58. Each attachment system

also consists of winch housing structures to protect from micrometeoroid impacts, spools for the cables,

and electric motors to unwind the spools. The total mass of the attachment system is 434.94 kg.

The spin up process will be completed using reaction control system (RCS) thrusters on both the ECHO-

MV capsule and the SLS Upper Stage counterweight. In case of necessary repairs or servicing of external

components to the spacecraft during Mars transit, sufficient fuel for three spin up/down cycles is carried

on the initial launch. To begin the spin up process, the spools completely unwind, after which an 11.86

m/s ΔV is completed using the thrusters. [52] Assuming a specific impulse of 235 seconds for the

thrusters and a safety factor of 30%, a fuel mass of 573.96 kg is required for one spin up/down cycle.

Thus, 1,722 kg of fuel will be carried for the entire Mars transit. This ΔV will create an angular velocity

of 3 RPM and approximate 5.05 percent head-to-foot “gravity gradient,” which satisfies crew comfort

criteria for dizziness and motion sickness. [52]

Table 4: ECHO-MV Mass, Power, and TRL Budget for Mars Mission Profile

ECHO-MV Launch Mass

Ma

ss

(kg

)

Po

wer

(kW

)

TR

L Continued Launch Mass

Ma

ss

(kg

)

Po

wer

(kW

)

TR

L

Payload Thermal [34]

(1) RMS [35] 500 0.55 8 (2) Radiator Assemblies 750 0 9

(2) ISPRs 1,600 2.0 9 Passive Thermal Con. System 50 0 9

ECLSS Active Thermal Con. System [25] 800 0.55 9

Air Revitalization [12] 447 2.6 9 Power

Temp/Hum. Control [12] 137 2.2 9 (2) XTJ Prime Solar Arrays 200 0 9

Radiation Shielding [45] 3,839 0 4 (4) Li-Ion Batteries 458 0 6

Fire Detection/Suppression

[16]

17 0.02 9 Propulsion

Crew Cabin 260 0 9 Bipropellant Hydrazine Thrusters 100 0 9

Water Recovery [37]

http://salotti.pagesperso-

orange.fr/lifesupport3.pd

f

734 0.5 9 Propellant Storage System 200 0 9

(1) Treadmill [16]

https://www.nasa.gov/mis

sion_pages/station/behind

sce nes/colbert_feature.html

220 0 9 Fluids

(1) Exercise Bike [16] 250 0 9 ECHO Dual Fuel (MMH/NTO) 1,500 0 9

(1) ARED Device [15] 1,000 0 9 Water/Ammonia Coolant [25] 300 0 9

Structures

Potable Water(93% Recycle Rate) 1,116 0 9

Central Structure 5,000 0 7 Artificial Gravity Options

Expandable Exterior 4,000 0 7 (12) Kevlar Tether Cables 24.76 0 4

(1) NDS Mechanism [38] 500 0.25 7 (12) Winch/Attachments 434.94 0 4

(1) CBM 250 0.25 9 Fuel for spin up/down cycles 1,722 0 9

EVA Airlock/Gas Storage 3,000 0.25 9 Launch Totals 29,591 10.57

Attitude Det. & Control Launch Totals +20% Margin 35,509 12.68

(4) CMG [23] 32 0.08 9 Additional Equipment

(Launched Separate)

Star Tracker [19] 4.4 0.016 9 (4) ISPRs 3,200 4 9

Sun Sensor [20] 0.21 0.0002 9 Food (Annual,1.83

kg/day/person)

8,056 0 9

Accelerometer [22] 2.6 0.008 9 Water (Annual) 2,587 0 9

Communications/Data

Handling

(4) EERs 1,600 2 9

(2) Radio Transceiver [39] 20 0.2 9 Repair Tools and ORUs 1,000 0 9

(1) 3.8m Parabolic

Antenna

17 0.1 9 Equipped Orbiting Total 46,034 16.57

Data Bus Architecture 100 0.5 9 Orbiting Total + 20% Margin 55,240 19.88

X-Band GaN Solid State

Power Amplifier [53]

5.6 0.5 9

Business Model The budget distribution entails years 2017-2037 and identifies various stages of ECHO mission

development. Prior to 2022, ECHO’s design and development of the ECLSS, structural components,

attitude control, power, communications and thermal control factors in $1,099 FY 2017, Million when

adjusted to inflation, with $291.53 Million dedicated to the production of the abovementioned

components of the module. These figures yield a total budget for ECHO at $1,390.72 Million without the

costs of launching payload into orbit.

In 2022 ECHO will be launched into LEO, with subsequent crewed missions and resupply cargo and fuel

launches increasing the cost of the budget of the module, totaling at $12,390 FY2017, Million at the end

of the mission in 2037. The given estimate also includes the Design and Development, Production and

Launch of the SatServ-1 and SatServ-2 missions, scheduled to be launched at the end of 2023 and 2025

respectively and yield a total of $3,000 Million in profits over the course of 10 years.

The high costs of the sustained mission of ECHO suggest establishing partnerships with Commercials

Entities and allocating certain percentage of the costs to them. Partnerships with Bigelow Aerospace,

United Launch Alliance, Lockheed Martin, Boeing and Orbital ATK will prove essential in the success of

the mission.

NASA will work on a 70/30 cost structure with the commercial partners, covering 70% of the program

cost. NASA, at the cost of $6,158.49 Million ensures sustained presence of at least 1 crew member and at

least 2 ISPRs onboard the module until 2037, and commercial partners split the cost among $6,162.21

Million, while yielding the highest net profit margin of all of the three options of $6,422.79 Million.

The 70/30 cost distribution between NASA and its commercial partners provides numerous benefits over

the other cost allocation options and ensures sustained success of the ECHO mission.

SatServ-1 will begin development in 2018 and cost an estimated $150M. Private contractors or ECHO

operators will be in charge of funding this mission. The production of each SatServ will cost

approximately $40M along with the Falcon 9 launch price of $148.8M. After the launch of SatServ-2 in

2026, the total cost for both SatServs to be fully operational in LEO will calculate to $677M. Based upon

the average cost of producing and launching a satellite into GEO, companies will be charged $50M per

mission. With the combined usage of SatServs, a total of six satellites can be serviced each year. If

SatServs are operational for ten years, they would yield an income of $3B. With that being said, ECHO,

as a whole, can generate a significant amount of profit while assisting numerous GEO satellite companies

with much cheaper solutions to minor satellite issues.

Figure 11: Yearly budget breakdown for NASA and commercial operator for ECHO and SatServ operations

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