Author Topic: A Framework for the MCT Propellant Depot  (Read 48307 times)

Offline A_M_Swallow

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Re: A Framework for the MCT Propellant Depot
« Reply #80 on: 10/02/2015 02:53 am »
The incoming MCT does not have to enter the centre of the Depot it could park in front. The arms could then grab the MCT and climb up the strut to the appropriate docking port. Those 6 vertical struts and their connecting horizontal struts would have to form the front (or back) of the depot.
You may be right, but it's a complex mass movement beyond my modest math modelling.

Alternatively does this need 6 docking ports? Are 2 sufficient?
One at the front and one at the back.

Offline Ionmars

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Re: A Framework for the MCT Propellant Depot
« Reply #81 on: 10/03/2015 12:39 am »
Alternatively does this need 6 docking ports? Are 2 sufficient?
One at the front and one at the back.
Certainly a two-vehicle propellants transfer is doable and has its place in the first few synods after the MCT is first put into service. We have this from Reply # 72 above:

"I now see different size classes of depots, where the number of vehicles accommodated at one time dictates different designs and modes of operation. The first is the single depot tank as proposed by  by ULA. The second is the Nadreck Depot with counter-rotation technology, and the third is the six-berth approach. Each has its advantages and disadvantages.

The ULA proposed depot follows a traditional approach whereby a depot is a storage tank in orbit.  It employs a cleverly designed shield over the tank that can be self-deployed while in orbit. Each visiting vehicle attaches to the orbital tank nose-to-nose and propellant transfer is vehicle to depot tank or tank to vehicle. When the depot tank is full it is ready to discharge its contents into the next vehicle, which will be an empty spacecraft that is bound for a BEO destination. This approach will do well for a long time, especially if space travel grows incrementally over a long period. It will not meet demand, however, if travel to Mars accelerates as suggested by SpaceX.

The next class of LEO depot could be the 4 + 1 Nadeck Depot. It has substantially greater capacity and is distinguished by the counter-rotational mode of operation for incoming delivery vehicles.

The third class would be the six-berth depot which may be distinguished by robotic arms operation and no depot storage tanks whatsoever (see update in a separate reply in the original thread re: "MCT and the Six-Shooter Depot").

Other classes could also be conceived."

The advantage of the 6-berth depot (its place in the scope of things) was spelled out in Reply #1 in this thread as follows:

"... the Six-Shooter Depot will feature the following advantages:

A. The arrangement will enable the following routine depot functions in an efficient manner:

(1) Each vehicle will receive the service of a cryocooler and boil-off control so it doesn't need to bring its own.
(2) Each vehicle will have the option of contributing propellant to a common storage tank at the Depot for later use, rather than always delivering directly to a destination-bound vehicle. This will provide flexibility in planning missions.
(3) "Extra" propellant stored at the Depot can be used to "top off" a nearly full tank, thereby saving an extra trip from Earth.
(4) Each vehicle will receive the service of an overpressure chamber during a propellant transfer.
(5) The Depot will also provide electrical service to each vehicle through the interface pad.

B. The six MCTs lying in parallel around a central cavity means that all berths will lie next to the robotic services area.   The robotic arms can move quickly and efficiently between the various vehicles to service them. These arms can grab and dock an MCT. They can push a fully loaded vehicle away from the Depot before its engines are fired up. They can replace repair parts on the Depot and on MCTs, if required.

C. The six MCTs lying in close proximity around a central core enables an efficient design for solar radiation protection. With a moderate increase in the size of a protective shell that would serve just one vehicle, six vehicles can be provided the same protection under one protective shell. Some reviewers of this proposal have questioned whether extra radiation protection would be required because CH4 has a higher boiling point than H2, the propellant previously considered to require a depot for long-term storage. CH4 will be easier to handle.

 D. A prominent aspect of the depot design is that it minimizes development cost. No new pressure vessels will be required for propellants because MCT tanks themselves will serve as the depot tanks. For the MCTs that provide their tanks to the Depot for long-term service, their propulsion units will be returned to Earth, if the final design of the MCT allows it.  No new pressure vessels will be required for humans because robots will conduct depot operations. If humans must attend to a special problem at the Depot, their visit will be short-term and their temporary habitat will be the Dragon capsule that brought them."
« Last Edit: 10/03/2015 12:40 am by Ionmars »
Could a Mars pole-vaulter set a new record? Not in a space suit. (smiley)