Our last DKos entry looked at the various spacecraft designs needed for the widely varying missions that our space endeavors call for.
However, the final piece missing from our jigsaw puzzle reveals itself: what happens when you need a pit-stop? The answer, just like in all of astronautics, is to bring it with you.
We will be discussing the various ways to quickly and easily replenish consumables used by our spaceships. Time and ease of operations are more important than any other factor (except safety, of course), so some things may be done in a different, less efficient manner.
Our gas station needs to have the following specifications:
OUV Resupply Module (ORM)
- Dimensions of a standard Habitation Module
- Hypergolic propellant refill
- Battery recharge
CM Resupply Module (CRM)
- Dimensions of a standard Habitation Module
- Atmospheric gases refill
- Battery recharge
Propellant Pressurization Module (PPM)
- Dimensions of a standard Habitation Module
- Cryogenic propellant refill
With these modules lifted into orbit and plugged into a Solar Power Station, we can replenish consumables in orbit, while simultaneously taking one step closer to declaring ourselves a true space-faring civilization.
Continued below the fold...
But before we continue, I must confess to an embarrassing act of reorganization.
The previous diary discussed the various space vehicles that were needed for our missions. However, during the course of writing this diary, it became apparent that the Geosynchronous Earth Orbit Transfer Vehicle (GTV) should have been categorized under the Space Ships heading instead of the upcoming Lunar Ships heading as originally planned.
So instead of updating the Space Ships DKos article, and asking the gentle reader to go back to it, I will present the description of that last vehicle in this article instead. So consider this section a continuation (Space Trucking, Part II?) of the previous article. The refueling article will appear after this section.
Again, my apologies. But, hey, at least DKos is helping me become better organized, right?
The GTV will have the following specifications:
- Dimensions that is larger than a 3rd stage rocket
- Uses on RL10B-2 Rocket with an extendable nozzle
- Pop up RCS Quads
The GTV will haul satellite payloads to SSEO or GEO.
GTV
The GTV is a larger version of the OTV. The LH2 Tank and the LO2 Tank/RL10 Engine are brought up by the Skylon separately, then assembled in earth orbit.
Once assembled, the payload is attached, and the rocket is fueled.
The GTV will have the following specifications:
- Dimensions of 4.7 m by 12.93 m (15.4 ft by 42.4 ft) less engine
- Empty weight of 4,513 kg (9,950 lbs)
- Uses 7,401 kg (16,367 lbs) of LH2 fuel
- Uses 43,431 kg (95,749 lbs) of LO2 oxidizer
- Uses Gaseous H2 (GH2) and Gaseous O2 (GO2) for tank pressurization
- Uses GH2 and GO2 for RCS
- Uses GH2 and GO2 for the Fuel Cell used for electrical power
GH2 and GO2 are used for tank pressurization, RCS, and electrical power because it is easier to operate this way.
The following is a summary of what a normal spacecraft uses for its propellant, pressurization, RCS, and electrical systems, compared to how we do it:
To add more confusion to the mixture, I inadvertently described the OTV in the previous article as using a battery for electrical power. Not so, space adventurer! Every feature that the GTV has, the OTV also has. They both use GH2 and GO2 for pressurization, RCS, and electrical power.
Since the OTV can lift payloads of up to 2,007 kg to SSEO, the GTV will be used to lift larger payloads to higher altitudes.
GTV missions:
- Maximum payload to an equatorial SSEO: 18,214 kg (40,155 lbs). A standard Hohmann Transfer and 33 degree plane-change requires that delta V1 = 2.016 kps, and delta V2 = 1.836 kps, for a total round-trip delta V budget of 6.845 kps.
- Maximum payload to an equatorial GEO: 11,209 kg (24,712 lbs). A standard Hohmann Transfer and 33 degree plane-change requires that delta V1 = 2.402 kps, and delta V2 = 1.888 kps, for a total round-trip delta V budget of 7.720 kps.
With the use of this vehicle, we can take over the entire satellite launching business. An
estimated launch rate of about one hundred (100) LEO satellites per year, and ten (10) GEO satellites per year is predicted over the next ten (10) years.
The Portrait
We can now see what the various vehicles look like in relation to the LEOS.
Our space vehicles are now complete. All that is needed is missions to fly and astronauts to fly them.
Oh, and propellant, of course.
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All vehicles run on some kind of propellant; alas, all vehicles therefore need to have their propellant restocked, otherwise the vehicle is useless. The analogy can be extended to a pistol: it is useless as a projectile-firing device if you can't replenish the projectiles.
Orbital Vehicle Resupply
Consumable resupply modules will be using standard habitat modules as its base. There will be two (2) different types of resupply Modules. Each module will have the following characteristics in common:
- Dimensions of 4.7 m by 11.0 m (15.4 ft by 36.1 ft)
- Weight of no more than 14,742 kg (32,500 lbs)
- Refurbished for reuse on earth, then brought up on a Skylon
The modules use a Solar Power Station for electrical power. This creates an Orbital Resupply Station (ORS). There will be two (2) types of ORS: the OUV ORS and the CM ORS.
OUV ORS
The OUV ORS replenishes the OUV, as the name implies. Each has the following specifications:
- LHe resupply (1 kW)
- UDMH resupply (1 kW)
- MON25 resupply (1 kW)
- Battery Recharger (4 kW)
- Total power requirement: 7 kW
- Total number of recharges: Four (4)
Three OUVs can dock at the OUV ORS, thus three OUVs can be replenished at the same time. That means that a total of twelve (12) OUVs can be recharged.
CM ORS
The CM ORS replenishes the CM, also as the name implies. Each module has the following specifications:
- LHe resupply (1 kW)
- LN2 resupply (1 kW)
- LO2 resupply (1 kW)
- H2O resupply (1 kW)
- Battery Recharger (4 kW)
- Total power requirement: 8 kW
- Total number of recharges: Six (6)
Liquid Nitrogen (LN2) and Liquid Oxygen (LO2) are used for the CM atmosphere, and the water is used for drinking, toilet, etc. Two CMs can dock at the CM ORS, thus two CMs can be replenished at the same time. That means that a total of twelve (12) CMs can be recharged.
The OUVs and CMs can now go about its various jobs, safe in the knowledge that a service station is just down the street, so to speak.
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Orbital Propellant Resupply
The OUV ORM and the CM ORM described above gives us the experience needed to perform cryogenic tank refilling operations, since LHe, LN2, and LO2 are all at cryogenic temperatures.
It is now time to go on to bigger and better things.
A Propellant Pressurization Module (PPM) supplies the pressurization needed to compel propellant from the refueling tank into the vehicle tank. The battery supplies the electrical power needed to operate the PPM.
Each refueling tank weighs 265 kg (584 lbs), and has a standard Docking port on one end. A Skylon Propellant Replenishment System is attached to the other end, similar to the system used to refill the Skylon spacecraft on the Spaceport Fuel Apron. This should help to vastly simplify refueling operations.
An OUV attaches to the docking port of the PPM and maneuvers it to a refueling tank, where it attaches to that as well.
The entire contraption is then docked with the GTV, where the PPM supplies the necessary pressurization needed to refill the GTV tanks.
Each of the PPMs will have the following specifications:
- Dimensions of 4.7 m by 11.0 m (15.4 ft by 36.1 ft)
- Weight of no more than 14,742 kg (32,500 lbs)
- Refurbished for reuse on earth, then brought up on a Skylon
- LH2 resupply
- LO2 resupply
- Total number of recharges: Three (3)
This means that the number of LH2 recharges is less than three (3) and the number of LO2 recharges is nine (9).
The GTV now have the freedom to stretch its boundaries and to go to places previous unreachable even by NASA.
Our city in space is now fully functional, complete with suburbs and now a gas station!
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In Closing
Because the folks at Reaction Engines, Ltd worked out an automated process for replenishing their Skylons with cryogenic fuel, we can use the same technology to refill our spacecraft. This is in keeping with our philosophy of reuse and commonality. This should help to lower design and production costs as well.
As the capability of orbital refueling becomes routine, we will truly begin to reach for the stars.
But we'll reach for the moon first. Of course, that's a story for another day.
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Cross posted at NMSTARG
With the humblest of apologies for any confusion, this technical paper is a fluid and dynamic process, and so the diary series has changed (again) accordingly. As you can see, there is a new item on the list. The DKos diary series so far:
- Overview
- History, Part I
- History, Part II
- Proposal
- Space Port
- Space Plane
- Space Stations
- Space Ships
- Space Refueling
- Lunar Ships
- Lunar Bases
- Lunar Propellant
- Startup Costs
- Revenue Streams
- Advanced Systems
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FULL DISCLOSURE: I work for the New Mexico Space Technology Applications Research Group (NMSTARG), a commercial space flight venture, which in its current form exists as an unfinished technical paper. NMSTARG is not affiliated with any of the businesses that were discussed in these posting. These diaries exists as a way for the DKos community to get a first look at our research, and to ask said community for any technical and non-technical (just as important!) feedback. The paper provides information on how to make a profit in space, detailing the infrastructure that will be needed and all of the associated costs involved. As such, we hope that it eventually attracts the attention of investors, where the paper then becomes the technical portion of a space-related business plan.
