"The power of equality is not yet what it ought to be."
– Red Hot Chili Peppers
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The need to connect one spacecraft to another whilst in outer space is self-evident. Additionally, the docking mechanisms need to be androgynous, where mirror images of each other can connect successfully.
Enter the design of one Mark Hempsell, BSc, MSc, PhD, Badass. His design should be the absolute standard for outer space connectivity.
Image 1: The Unpressurized Hempsell Docking Ring concept.
The Hempsell design uses similar Capture Rings and pedals as the design from QinetiQ Space nv to bring a misaligned spacecraft back into alignment (soft dock) (Image 1). The Capture Ring then brings the two spacecraft together where locking pins are tripped, allowing for a more permanent attachment (hard dock).
The Hempsell Docking Ring (HDR) specifications are all within USIS tolerances (see Table below).
BERTHING RING WIDTH |
0.175 |
m |
OUTER BERTHIBNG RING |
1.624 |
m |
INNER BERTHING RING |
1.600 |
m |
OUTER CAPTURE RING |
1.575 |
m |
INNER CAPTURE RING |
1.525 |
m |
CAPTURE RING PROTRUSION |
0.140 |
m |
UNPRESSURIZED HDR MASS |
48 |
kg |
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USIS PRESSURIZED VARIANT
The Hempsell Docking Ring (HDR) concept is critical for the exploitation of outer space. However, the connection becomes very limited if humans and cargo cannot pass through the rings in a pressurized environment.
Enter Mark Hempsell, BSc, MSc, PhD, Badass, once again.
Dr. Hempsell's rather clever pressurized design is a marriage between the QinetiQ Space nv and the Reaction Engines, Ltd. designs, all ramped up to The Standard (Image 2).
Image 2: The Pressurized Hempsell Docking Ring
The pressurized version of the HDR is composed of an unpressurized HDR along with a pressure bulkhead and hatch.
The USIS specifications state that the pressurized passageway through the pressurized connection must be wide enough to allow for astronauts in EVA suits and International Standard Payload Racks (ISPR) to pass through.
Dr. Hempsell ensures a USIS compliant hatch. The specifications for the pressurized HDR are listed below (see Table below).
HATCH LENGTH |
1.400 |
m |
HATCH WIDTH |
1.000 |
m |
HATCH THICKNESS |
0.046 |
m |
HATCH AND BULKHEAD MASS |
32 |
kg |
PRESSURIZED HDR MASS |
80 |
kg |
Dr. Hempsell has a few examples of the HDR in action on his website. One image displays two pressurized HDRs with the hatch open, and another image with a space capsule with a pressurized HDR located on the spacecraft's nose.
The Hempsell Pressurized HDR will allow for easy connectivity and access between spacecraft.
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USIS PROPELLANT TRANSFER VARIANT
The Hempsell Docking Ring (HDR) will be utilized to accommodate the most important task in all spaceflight operations: orbital cryogenic propellant transfer.
There will be two versions of the propellant transfer HDR, with both versions starting with the unpressurized HDR. The first version will be able to receive propellant (Input) and the other version will provide the propellant itself (output).
Reaction Engines, Ltd. (REL) has an excellent idea of how to transfer propellant using their Skylon spaceliner. It looks to be a variant of the old Apollo–style Probe and Drogue style of connectivity, where one probe loads the Liquid Hydrogen (LH2) fuel, whilst the other probe loads the Liquid Oxygen (LO2) oxidizer (Go to the 01:38 mark in the video below).
We hope to adopt the same idea in space. The scenario envisioned is to dock a propellant refill module to an empty vehicle using the HDRs. Probes will then extend from the refill module into receptacles in the receiving vehicle. Once a solid connection has been established, three cryogenic fluids will be pumped aboard: LH2, LO2, and Liquid Nitrogen (LN2).
The Input Variant of the HDR includes all of the infrastructure needed to handle the cryogenics, and adds 32 kg to the overall mass, for a total of 73 kg.
The Output variant includes the infrastructure needed to deliver the cryogenics, and adds 43 kg to the overall mass, for a total of 91 kg.
The Table below summarizes the masses.
PROPELLANT INPUT HDR MASS |
73 |
kg |
PROPELLANT OUTPUT HDR MASS |
91 |
kg |