Exploring the possibilities for 9m diameter space systems


Starship Human Landing System (HLS) Concept image credit: SpaceX

So many possibilities for 9m rocket systems and the standard components they use.

A 9 meter rocket and fairing/payload bay opens up a dramatic news set of space exploration and utilization possibilities.  This exploration uses SpaceX's Starship systems as the baseline technology as it is by far the most advanced in development and testing.

In the rendering to the right we see a SpaceX generated image of used for the NASA Lunar Human Landing System (HLS) competition.  It uses the bottom 2/3 of a standard Starship but then customized the top 1/3 for HLS operations.  It uses 3 vacRaptors since it is not intended to return to Earth surface.  This sort of specialized payload area and engine set is key to using the Starship "space frame" for many missions and applications.

Beyond this, "One-Way" Starships that won't return to the Earth surface can have the huge tankage (the bottom 2/3), which is engineered for high pressure, converted to air pressurized work, living or recreational space one it reaches it's destination.

A "Widget" is a multi-function standardized component

Key Proven Supporting Widgets

Falcon 9 / Crew Dragon

Currently only non-Russian access for humans to LEO.  Abort safety assured with Super Draco thrusters.  Carries up to 7 for 1 days trips up to and back from LEO.  Can stay by itself in LEO for up to 10 days ... 6 months connected to a larger ship that supplies air ... power.  Estimated price of $120M per round trip. 

International Docking System Standard

The IDSS docking mechanism is androgynous, uses low impact technology and allows both docking and berthing. It supports both autonomous and piloted docking and features pyrotechnics for contingency undocking. ref: Wikipedia

ISS Life Support

The critical systems are the atmosphere control system, the water supply system, the food supply facilities, the sanitation and hygiene equipment, and fire detection and suppression equipment. ref: Wikipedia

NASA Glenn Space Power Facility

This facility is the world's largest space environment simulation chamber (100 ft in diameter by 122 ft in height) and is used to ground-test large space-bound hardware. It can simulate the severe conditions of space such as vacuum, low temperatures, and unfiltered sunlight.

Key Emerging 9m Baseline Widgets

SpaceX Cargo Starship Body

SpaceX's Cargo Starship is 9m diameter, stainless steel, Liquid Methane and LOX fueled, orbitally refuel-able, fully reusable rocket system that can carry 100+ tons of any payload type to LEO, and with refueling, the Moon, Mars and beyond.  It is expected to start commercial operation in late 2021, cost less than $100M for a ship, and less that $10M per trip to operate to LEO, and return for reuse. Note, image is an old render by SpaceX

3 Types of Raptor Engines

SpaceX is planning 3 types of engines.  All are throttle-able (between a min and max thrust) and highly re-usable.  The first is a Raptor engine that can be gimbled for direction of thrust control.  This is needed for soft landing back on Earth. The second is a fixed Raptor engine.  The final type is a VacRaptor engine that is designed to be optimal in the vacuum of space. Note, photo by SpaceX

SpaceX "Stock" Crew Starship

Many concepts here center on modifying the top 1/3 of a "stock" or "standard" Crew Starship (the area above the fuel tanks) into mission specific designs.  Crew Starships are expected to be human rated for crews of up to 100.  Possible testing in 2023 and operations in 2025. Note, image is an old render by SpaceX


The Super Heavy Booster with a Crew Starship stacked on top (2019 data). The Super Heavy Booster has the SpaceX logo on it.  How did they get here?  Check out an engineering history of Starship by clicking here.  Image credit reddit

The Super Heavy Booster is the foundation of the Starship system

Starship is a two stage system, like Falcon 9, but much larger with a fully reusable upper stage option.  It's huge 9m wide rocket body and tanks are built out of very low cost thin Stainless Steel and it fueled by very low cost super-cooled cryogenic liquid Methane and LOX. The first (or lower) stage has between 20 and 30 Raptor engines that lift the upper stage to 2.5 km/s and 50 km before coming back to the launch pad area (much like F9 does in a Return To Launch Site recovery).  WidgetBlender assumes a build cost of $200M and an operational cost of $10M per launch.  The Super Heavy Booster needs to have at least 10 times reuse to make the system much lower cost than Falcon Heavy ... WidgetBlender won't suggest any changes, combinations or additional uses for the Super Heavy Booster (and thus it's not a widget).


In space it's not the distance, its the change in velocity that your fuel/engine combination can create that matters most to what you can deliver to a place.

Potential Types of Starships

For LEO and beyond operations GEO, Moon, Mars ... the SpaceX Super Heavy Booster is needed to put a Starship and 100 tons of payload into LEO.  It is assumed that the Super Heavy Booster is a $200M machine that will be reused maybe 100 times.  Cost per mission is thus assumed to be $10M with operations, fuel and maintenance.

SpaceX official efforts:

A Cargo Starship is a re-usable ship that can return to Earth surface, and be re-used 10s or 100s of times.  It is the SpaceX reference design.  WidgetBlender assumes it's to cost to build is $100M, but may perform 10s or perhaps 100 missions ... bringing mission cost down to perhaps $10M with operations, fuel and maintenance.

Design types used for concept exploration at this site do not have a return to Earth capability, thusnthey are somewhat less expensive than a Cargo Starship since they do not have TPS, fins, header tanks and only 3 VacRaptor engines (vs 7 Raptors).  All of these types are assumed to have a $50M build and launch cost.

This is in active development and testing at SpaceX's facilities in Texas.

Crew Starship adds life support and other forms of human support to a sealed pressure vessel in the cargo bay of a Starship, as well as hatches for crew and cargo loading and unloading. Any long term Crew Starship including the Mars Crew Starships add to this a large solar array and radiator, larger landing legs, a large airlock and elevator from 35m to the surface.

HLS Starship (shown at top of page) has been proposed to NASA by SpaceX as a ship that can ferry cargo and crew from the Lunar Gateway to the lunar surface and back.  It needs to be launched to LEO and refueled there before proceeding to HALO type Lunar Orbit before docking with Lunar Gateway and performing its mission.  HLS Starship removes structures from the Cargo Starship needed for Earth re-entry such as fins and TPS, but adds a crew area with life support, a small cargo bay, airlocks, solar power cells, soft lunar landing thrusters, surface insulation and wider landing legs.  It is unknown if NASA will pay to proceed with this concept beyond studies and component tech development.

SpaceX potential efforts (Per Elon Musk comments):

Fuel Depot Starship (see image below) is key as nearly all missions beyond LEO and GTO will require orbital refueling.  

Earth Point to Point Starship (Sub-Orbital) is the only Starship Concept that does not need a Super Heavy Booster is a Starship Sub-Orbital flight of perhaps 10,000 km from one point on the Earth to another.  While some have suggested this is a competitor to "first class" airline flights since these flights are 30 min vs 6 hours ... the lack of airline systems integration suggests that it will serve a space tourism market first.  It will be quite a 30 minute ride with a 3g launch, 300 km above Earth views, 10 minutes of weightlessness and a fiery re-entry.  Virgin Galactic is charging $250,000 for lesser experience.  This Starship carries 50 passengers with layers of safety systems.  At $50K - $75K per round trip there will likely be many takers.


Starship Power Notion

Starship Mission Power Needs

Crew Starship

The ISS requires between 75 to 90 kilowatts of power ... (enough to power 40 average homes).  Since Starship will not be running numerous experiments (but supporting more people) a reference estimate of of average consumption of 50 kW seems reasonable.

Cargo Starship (Including fuel runs)

Although it probably requires less lets use 5 kW as an average consumption, but moving of control surfaces on atmospheric entry will require much more, but maybe for only 10 minutes.  The system may need to supply 50 kW at high voltages and amperage during these phases.

Powering Starship in Flight

Starships will need electrical power to operate.  Some Starship operations will need different levels of minimum, average and peak electrical power.  In all cases a Telsa battery will be needed in phases of operation where power generation is not possible.  It seems that Model S 85 kWh battery packs: 540 kg each, 375 volts are being used.  For duration and redundancy all solutions will need at least 1 mT of Tesla battery.

Power options:

Lithium Batteries (DC Power) 

Charged before a mission Lithium Batteries can supply the electricity needed for a short LEO satellite deployment mission and return to Earth surface for re-use.

Cargo use (5 kW) has 34 hours ... plenty for LEO, MEO and GEO operations.  So 1 mT total.

Batteries would not last long with a 50 kW Crew demand.  So something more is needed.

Methane-Oxygen Generator (AC -> DC Power)

For longer missions a Methane-Oxygen Generator could recharge the batteries.

1 cubic meter of liquid methane (424 kg) expands to create 593 cubic meters of methane gas.

A 100 kW generator uses 1308 cubic ft/hr of gaseous methane = 37 cubic meters per hour + the needed gaseous oxygen.  So that generator can create 1600 KWh with 1 cubic meter of liquid methane (424 kg).

With a mixture ratio of 3.55 (O2 to CH4) ... the generator will need 3.55 kg of O2 for every kg of CH4.  Thus 1,505 kg of O2 for 424 kg of CH4.  Total fuel need is very close to 2 mT for 1600 KWh of power.  So for a reference 100 kW needed on average very hour this 2 MT of fuel would provide 80 hours of 100 kW power. 
For Cargo levels (5 kW) 1600 hours.  Assume 500 kg generator mass. Assume 500 kg radiator mass.

Methane Fuel Cells (DC Power)

A conventional combustion-based power plant typically generates electricity at efficiencies of 33 to 35%, while fuel cell systems can generate electricity at efficiencies up to 60%.  This points a Methane Fuel Cell producing nearly twice the power of generator with the same fuel.  Thus 1 MT of fuel would provide 80 hours of 100 kW power for Crew levels of use.  Assume 250 kg fuel cell mass. Assume 500 kg radiator mass.  A 5 day crew mission would thus need about 2 mT of mission mass for power.

For Cargo levels (5 kW) one could use just 0.2 mT of fuel 320 hours (10 days = 240 hours).  A small fuel cell and radiator might only add up to 300 kg.

For a 10 day Cargo mission the mass needed for power could be as low as 500 kg. 

Solar Arrays (DC Power)

On Crew missions of over a week there will be no substitute (except someday nuclear power) for solar arrays as a Methane generator or power cell will consume too much mission fuel.

Solar array potential power of up to 200–250 W/kg is possible with new designs.

50 kW = 250 kg  (light but bulky)

But in most applications Starship is at least part of time in orbit ... so effective power is 1/2.  If Mars bound size for lower solar flux at Mars.  In both cases multiply by 2.

Thus 50 kW = 500 kg

Assume 500 kg for Starship specific machinery for optimal pointing. Assume 1 mT radiator mass. For a total of 1500 kg for power generation ... buffered by 3 Telsa Model S type powerpacks for a total of 3.5 mT for power.


For LEO, MEO and GEO Cargo use of 2 Tesla Model S powerpacks powered up at the launch pad should work without solar arrays for most Cargo missions (assuming less than a 24 hour mission length).  1 mT total

Cargo Mission to Lunar Orbit (10 day) might use methane fuel cells (500 kg total power mission mass), although a 20 x 10 m conformal Solar Array might prove to be a better use of the mass budget.  A 2 Tesla Model S powerpacks will be needed for some phases of operation. 1.5 mT total.

Mars Cargo missions will use probably need a 20 x 20 point-able Solar Array (non-conformant) with radiator. plus 2 Tesla Model S powerpacks for 2-3 mT total.

All Crew missions over 5 days would probably choose a large point-able Solar Array (non-conformant) with radiator.  For launch, initial operations, prep for atmospheric entry and landing 3 Tesla Model S powerpacks will probably be needed. 3.5-4.5 mT total.


Unmanned Fuel Depot in LEO ... based on a lighter "One Way" Cargo Starship with 3 VacRaptor engines, no flaps, no TPS, no header tanks and an ejected fairing instead of a cargo bay.  Sun shield, solar array, radiator and robot arm added.

Inexpensive LEO Refueling Is Key to any mission beyond LEO and GEO

The huge size of Starship require a lot of fuel to move from place to place.  Missions to the Moon and Mars will require from 50% to 100% refuel in LEO.  The best way to accomplish this may be a LEO Fuel Depot (see below) that can be completely refilled with 8 - 10 payload-less Cargo Starship flights ... then the mission ship docks and quickly fills up.  Hopefully these fuel missions will be based on a very reusable Cargo Starship that can deliver a load of fuel for $5-10M.  This would require at least 10x reuse of a Cargo Starship.  Elon Musk has suggested the need for a Fuel Depot as part of the NASA HLS proposal.  WidgetBlender imagines it might look like the following.  A sun shield minimizes fuel boil-off ... but the depot must be actively pointed nose toward sun to maintain this.  Integrated solar panel capture power for operations, including internal gyros and a optional robotic arm that can be use to move cargo between two ships. 

Note that if launch rates are high a single Cargo Starship can act as a short term Fuel Depot.  Once in orbit with 150 mT of fuel, other Cargo Starships bring to it 150 mT of additional fuel at a time, until the fuel needs of the mission Starship are available.  The mission Starship (Crew, Cargo or HLS) is launched, docks with the "short term Fuel Depot" Cargo Starship, transfers all the fuel to itself, then departs for the mission.  The Cargo Starship then return to Earth surface.


Sub-Orbital Earth Point-To-Point Tourist Starship (50 passenger capacity)


Just Off-Shore Tourist Starship Launch - Land - Inspect - Service Facility

9mDesign possibilities: 

9mDesign emphasizes large modules that are ready to automatically deploy and operate as soon as they are on the lunar surface. This allows for complete fabrication and testing in the comfort and cost efficiency of a normal environment. The goal is to minimize the need for humans to perform construction and maintenance in a vacuum. That time is better spent in productive activities or even simple tourism.

"Space Tug" Starship does have a cargo bay and remains in space and is refueled in LEO. It can take cargo from a Cargo Starship and then transport it to any other destination in space. From some orbits, if properly fueled it can again return to the LEO depot and repeat the process. Space Tugs are created when a Starship carries a payload that takes up more volume than a Cargo Starship can carry, say a 11 m wide structure for LEO or the Lunar Surface. With the proper nose-cone on a cylindrical payload it can be launched with minimal performance penalty (soft of like Skylab did on a Saturn 5). But without the standard skin and TPS of a Cargo Starship it's can not return to Earth surface ... so it must stay outside Earth's atmosphere. So after it accomplish's it's non-lunar surface "launch mission" (lunar surface missions don't reserve enough fuel to return to LEO for refueling) it can then return to LEO and be refueled in orbit to carry a Cargo Starship conforming payload anywhere in the Solar System. But one more widget is needed to make this work, namely a "8m Pallet".


Space Tug with Lunar Capable Landing Legs at Manned Fuel Depot

8m Pallet (graphic below) is an vehicle that allows a Cargo Starship to drop off a payload (up to 100 tons) in orbit and have connect to the top of a Space Tug Starship. Only 2 meter high it still leaves 15 meters for payload height. It has cold gas thrusters to dock to the top of the Space Tug. The pallet has deploy-able solar arrays for power. At this point the payload could be sent anywhere in the solar system depending on payload mass.

If the mission is the lunar surface, pop out landing legs, a ramp and 4 Super Draco engines to lift the payload off the top of the landed Space Tug and drop it gently down on the lunar surface.  


8m Pallet


Payload on 8m Pallet (using cold gas thrusters) separating from a Cargo Starship


After drop off by Cargo Starship the 8m Pallet (now with Solar Panels deployed) uses gas thrusters to dock and latch to waiting Space Tug.  If bound for the Lunar Surface it will need a DV of nearly 6 km/s.

It takes less DV to get to the surface of Mars than the Moon since you can aerobrake at Mars.

Space Tug To Mars (minimum DV needed: 3.8 km/s)

A fully LEO fueled Space Tug can carry a substantial payload to Mars in combination with our 8m Pallet.  Unlike the Moon it's the final trip for this Space Tug, but for a $50M hardware investment it may have completed a mission to LEO, multiple missions to the Moon and a final mission to Mars.  During that time it may have used over $200M in fuel ... but like an airliner fuel costs eventually dominate vs the cost of the vehicle.

In this case our Space Tug enters the lower Martian atmosphere engines first, using it's remaining fuel to both slow it and cushion it from the heat of atmospheric entry, slowing the vehicle.  At the right moment (just before the Space Tug melts) our 8m Pallet disconnects from the Space Tug and ejects parachutes.  The Space Tug, now far in the distance, soon begins to melt and tumble and break up ... but the 8m Pallet with the payload is now being slowed by the chutes.  A coating of ablative heat shield helps keep the palette bottom from melting. As the chutes near their thermal limits the Super Dracos fire to slow the pallet ... cold gas thrusters fire to balance the load ... eventually bringing it to a soft vertical landing on the surface, with up to 100 tons of supplies and equipment.


Space Tug, 8m Pallet (Solar Panels retracted) attached payload enter Mars atmosphere ... legs now glowing hot to help aerobrake the vehicle.


Chute deployment, heat shield on bottom of 8m Pallet glowing hot, SuperDracos firing

Expendable Cargo Starship is a ship that is not capable of returning to Earth, performs one mission. This boosts mission performance at the cost of the vehicle. An Expendable Cargo Starship can carry structures even wider that 9m to destinations in space. They may be used as on orbit "stages" for very large or very fast deep space missions. Elon Musk has suggested it may be a useful varient for some missions.

"One Way Crew-able" Starship is a ship that is deployed to LEO, Moon or Mars with dedicated machinery attached to it. The Starship body becomes part of the operational system. Fuel tanks may be converted to pressurized space for use once the Starship is deployed.

You can get many uses from a Starship that can't re-enter ... many deliveries to GTO and one to the Lunar Surface or Mars atmosphere.

Planetary Defense Starship (PDS)

Combining 4 regular One-Way Starships cores around a modified One-Way core can allow for planetary defense against a Million Ton Asteroid (MTA). This weapon, if it hit a MTA 2 months before Earth collision it would change the MTA's velocity enough to change it's position by 2 Earth diameters ... a very near miss ... but a miss.  Mission cost $500-$750M.  In the following render the payload on the core Starship is special.  At about 100 tons it contains string Starship connectors, SuperDraco thrusters and fuel for terminal divert and a (blue) inflatable impact enhancer that expands to the diameter of the target before impact.    During the final minutes of thrust impact assessment sensors are dropped off to record the impact results ... this allows them to trail the impact.  After the end of thrust a single lander launches from the front to get a few weeks ahead of the rest, then drop a small 10 kg payload onto the surface to aid terminal navigation.  Three NEODAT (Near Earth Object Detection and Tracking) satellites carefully track and calculate the needed trajectory down to a meter.  The PDS also payload contains the Deep Space Atomic clock that the NEODATs listen to help calculate the any final thrusts with the SuperDracos.


Planetary Defense Starship (40 re-fuel trips needed, 5 Starship cores expended)

Space Stations

How can Starship support or be used as part of LEO Space Stations?

NASA Compliant ISS Follow-on Microgravity Space Station (Delta Station)

Per the NASA Administrators suggestion, in this concept three OWCIS (One Way Crew Inhabitable Starships) are joined to a central docking hub (bought up in a Cargo Starship cargo bay) in LEO.  An additional hub with ROSA (Roll Out Solar Arrays) is added to complete the station.  The deployed solar arrays remain pointed at the sun with the Starships mostly shaded.  This allows for highly conductive skins on the Starships to act as radiators (since they are 90% shaded).  One Crew Dragon per Starship remains connected as a life boat ... leaving 2 docks (on ends of the hubs) open for any ISS complaint auto-docking vehicle to dock.  Pressured space is approximately 2500 cubic meters to start with (2.5x the ISS) and option to convert fuel tanks to expand to more than 8500 cu meters.  Number of crew is "lifeboat capacity" limited to 21.  Cost to build and deploy is around $2-3B.


Starship based microgravity "Delta" Space station (2030)

Single Starship Space Station

In this concept OWC Starship is placed into LEO with no crew. The top 1/3 of the this OWCS is stuffed with parts needed for build out: air, water, supplies, a ROSA (Roll-out Solar Array) and Radiators (which are both automatically deployed soon after arriving at LEO). Life support is automatically started and validated so that Crew Dragon, Starliner, Orion or a stock Crew Starship can dock and the "construction crew" can board.

The tanks in the OWCS are then converted to living space ... providing up to 2,000 cubic meters of living space. The depiction shows a notional set of "decks" to provide some idea of scale. The tank build-out may be based on cutting open the top of tank domes and then welding hatch doors to those areas ... probably a 3m type hatch with air, water and power feed connects built in. An large inflatable kit is placed each tank and automatically expands to provide insulation, wires and lead detection to the tank interior skin. Next a set of rigid wall frames are attached to the hatches and put together.

Key Issues:

1) Under powered, may need more solar cells
2) Post launch orbital converting of tanks has never been attempted
3) Staff limited by on-station lifeboat capacity (15 max)
4) 2m "Starship class dock" has no been proposed by SpaceX

Great Reddit comments! Click here 


Depiction of a Single Starship Space Station (S4)

"Wide Fairing" Space Station Module

Given that F9 has a fairing shape that allows the fairing diameter to be about 25% greater than the first stage diameter I created a notion that extends this concept to Starship. Also, just as the F9 has legs that bump put from the rocket body, I suggest some bump outs that contain Roll-Out Solar Arrays and the Radiators that are deployed on orbit. This creates more useful interior space and better balances the design. The tanks area at least provides some good structure, and could be converted to pressurized space. Finally I include 3 2m wide hatches for Starship to Space Station connections ... or connections between these modules.


"Wide Fairing" Space Station

Starship Based Zero to Low Gravity "Hotel"

In this concept three OWCIS (One Way Crew Inhabitable Starships) are docked in LEO around a central hub (brought up by a Cargo Starship). A second hub is connected ... guide wires are then connected to bottoms of the OWCISs to provide stability (from both hub 1 and hub 2). Solar collectors are unfurled from the second hub to provide power. A fourth stock Crew Starship is then docked with the first construction crew at hub 1 to act both as a long term "lifeboat" and a long term micro-gravity area for recreation. The tanks in the 3 OWCISs are then converted to living space (see Single Starship Space Station concept above). The assembly is then slowly spun up to provide spin gravity as high at 0.25g at the Starship base.

The 0.25 - 0.2g decks (near the bottom of the Starship's converted tanks) provide more normal hygiene and dining. This creates about 2,500 cubic meters of space for each OWCIS for a total of 8,500+ cubic meters in the facility total. The Crew Starship rotating along the hub axis still offers micro-gravity experience opportunities even as the facility slowly spins. The facility keeps the solar collectors pointed at the sun. While the views from the facility slowly rotate ... the fast changing view of the earth that fills the windows obscures the rotational effect. One other Crew Starship can dock at hub 2 for passenger transfers. Note that Crew Starships need to have a hatch (I suggest a special 2m hatch) at the nose to allow rotational matching.

Key Issues (High Risk Concept):

1) Stability ... the spinning top issue
2) Variable gravity across decks can cause motion sickness
3) Needs more solar cell area

Reddit comments here


Depiction of a Starship Based Zero to Low Gravity "Hotel"

Starship Cargo Bay Compliant Space Station Module

The Starship Cargo Bay can accommodate a small space station, which can be linked together at the end.  The curved plates are fold out radiators pointing toward the back of the space station.

The facing side is left blank in this depiction so you can get a feel for size and volume.


Starship Cargo Bay Compliant Space Station Module

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