Author Topic: Maintaining health on a Mars-bound Starship (Read 46681 times)

Ionmars · « **on:** 09/19/2022 02:20 pm »

NASA and various universities are studying the effects of extended microgravity missions on human health. We now know that affected organs include the heart, brain, eyes, and nervous system. For example, astronauts arriving at the ISS find their blood is pushed “upward” from the legs and abdomen toward the heart and head, which leads to swelling of the face and head. A build-up of fluid within the skull increases brain pressure, which can cause hearing loss, brain edema and a deformation of the eye known as Spaceflight Associated Neuro-ocular Syndrome (SANS). Extended exposure to microgravity also causes atrophy of muscles that constrict the blood vessels and reduce control of blood flow. (1)

Studies have found that exercise in space will help maintain many types of cardiovascular fitness. Currently, research at the ISS is directed toward learning more about SANS and toward developing countermeasures to the many cardiovascular changes. However, the best known health protection for extended missions is to provide artificial gravity. (2)

This thread presents a series of sketches to illustrate one approach to provide artificial gravity for crew and passengers in transit to Mars on Starship. Alternative methods are welcome..

1. https://www.nasa.gov/mission_pages/station/research/station-science-101/cardiovascular-health-in-microgravity/
2. Frank Tavares, Goddard Spaceflight Center, “Artificial gravity provides partial protection for biology in space,” Phys.org, Sept 7, 2022.

Ionmars · « **Reply #1 on:** 09/19/2022 02:22 pm »

This approach addresses the following requirements:

1. Provide artificial gravity for crew and passengers in transit to Mars and the return trip.
2. Allow for landing on Mars and EDL upon return to Earth.
3. Utilize known variants of Starship with minimal modifications.

This approach also adopts the following design strategies:

1. Keep it simple.
2. Exploit Ionmars’ method for LEO refueling by hard-docking Starships onto an in-space accumulator.

Re: Starship In-orbit refueling - Options and Discussion
« Reply #1086 on: 07/11/2022 10:44 am »

Ionmars · « **Reply #2 on:** 09/19/2022 02:23 pm »

One assumption of this approach is that SpaceX will develop five variants of Sta4ship:
1. A vanilla Starship to launch routine payloads into LEO.
2. An ~~HSF~~ HLS starship for Artemis program that is stripped of its heatshield and can land on the moon, but has no capability to return to Earth.
3, A accumulator (depot) Starship for refueling other Starships in space and that cannot return to Earth.
4. A tanker Starship that specializes in delivering propellants to an in-space accumulator repeatedly and returning to Earth.
5. A crew Starship that can land on Mars and on Earth.

Of these variants, this approach employs only two for the Mars journey: a crew Starship and an accumulator Starship. Together they could carry crew and passengers to Mars in relative safety and good health. I call this combination “dual Starship.”

Other activities, such as delivering payloads to Mars, may occur concurrently with a crew transit to Mars

Ionmars · « **Reply #3 on:** 09/19/2022 02:24 pm »

The first steps to employ dual Starship would be to establish an accumulator in LEO and fill it with CH4 and O2 propellants. This may require seven trips of a tanker from Earth to accumulator, which involves repeatedly docking onto the accumulator’s docking posts.

The next step would be to launch a Mars-bound crew Starship to the accumulator to be refilled all in one operation. At the end of refill, both ships would still be docked together as shown in the sketch below. Rather than separating, the two ships would fire their Raptors simultaneously to send both of them into trans-Mars orbit.

Ionmars · « **Reply #4 on:** 09/19/2022 02:25 pm »

A large volume of propellants will be required for TMI, for balancing mass of accumulator ship with the
mass of crew ship during transit, and for velocity reductions at the Mars end of the trip. OTOH, having just refilled crew Starship, most of the propellants would now reside inside the crew ship tanks. A detailed analysis of this journey may find that more propellants are needed in the accumulator before Mars TMI. In this case, vehicles would separate temporarily while additional tankers refill the accumulator. When tanks in both vehicles were full, they would rejoin to each other and fire up their engines for TMI.

Ionmars · « **Reply #5 on:** 09/19/2022 02:26 pm »

After the final TMI burn, the pair of ships would separate and re-orient tail-to-tail. They would rejoin by employing an inter-ship fairing, which may just comprise a series of latches attached to the bottom of the accumulator. The bottom of crew Starship would be equipped with receptacles to accommodate the latches. This equipment would be attached before vehicles were launched into space and should be a minor amendment to the surface of their engine sections.

The pair of ships, now joined, would use their thrusters to begin a slow spin around a common center of rotation. At 50m from the common center , crew would enjoy an artificial Mars gravity when revolving at 0.35rpm. Earth gravity would occur at 1.35rpm.

Ionmars · « **Reply #6 on:** 09/19/2022 02:28 pm »

During their trip to Mars, crew and passengers would experience sharp changes in gravity. Launching from Earth could require up to 4 g followed by a zero gravity interim while the two ships separate and rejoin. This would be followed by gradual increase of artificial gravity as dual Starship begins to rotate, perhaps up to 0.38g during the principal segment of a journey lasting 3 to 6 months.

During their transit to Mars, crew would also experience reversals in the direction of gravity force. During launch they would be forced “downward” into their seats, which would be toward the propellant tanks and engines. When artificial gravity took s effect downward gravity force would be toward the nose of the ship. Design of the crew cabin interior must accommodate these reversals.

Ionmars · « **Reply #7 on:** 09/19/2022 02:28 pm »

One way to accommodate gravity reversals is to design a gravity couch that can adjust to both takeoff and artificial gravity during transit. A gravity couch that could be removed from the floor and latched onto the ceiling would meet this requirement. This couch could be incorporated into an arrangement of sleep/EDL cubicles inside one level of a multi-level crew cabin, as suggested by the sketch below.

The sketch shows a possible layout of sleep/EDL cubicles. Each cubicle, which resembles one slice of a doughnut, could contain six 2m-long bunks for a compact travel arrangement similar to a submarine. With seven cubicles on one level, this option could accommodate up to 42 crew and passengers. Alternatively, a cubicle could be designed with 5, 4, 3, 2, or 1 bunk(s), perhaps depending how much volume a wealthy traveler might purchase for his own use. Also, if the aisle into the cubicle were located on one side, it would allow room for a double bunk on the other side of the cubicle.

The 1m 2.0m wide cubicle is divided into thirds, so the aisle from the common floor space into the cubicle is only ~~0.34m~~ 0.67m wide at the entrance. Each bunk is also ~~0.34m~~ 0.67m wide at the narrow end, but widens out to +/- 1.25m on the other end.

A launch couch, seat, or pad would be tailored to the length and body curvature of each traveler. It would latch onto the floor of each traveler’s bunk for launch. When artificial gravity began during transit, each couch would be detached from the bunk floor and reattached to the ceiling, which would now become the floor.

Ionmars · « **Reply #8 on:** 09/19/2022 02:30 pm »

While ship rotation is in effect, mass balance should be maintained between accumulator and crew Starship. The objective would be to minimize wobbles and uneven gravity acceleration. Before the mission was launched, engineers would calculate an initial mass balance, taking into account mass of personnel, equipment, and fuel in the crew ship versus the mass and distribution of propellants in the accumulator. While in transit, some adjustments may be feasible by rearranging payload in the crew section and by pumping propellants to different locations in the accumulator tanks. However, some wobble may be unavoidable when people move around inside the crew ship.

Upon approach to Mars dual Starship would decelerate to zero and separate into its two component ships. The accumulator would decelerate into Mars orbit, to be reused at a later date. Crew Starship would descend through EDL and land at Starbase Mars.

Ionmars · « **Reply #9 on:** 09/19/2022 02:31 pm »

When Starbase Mars becomes sufficiently developed to support a launch to Mars orbit, a return trip to Earth could be planned. A series of tanker flights would deliver propellants produced on Mars to the accumulator in Mars orbit. Then crew Starship would launch to the accumulator and join it in the same manner as was done in Earth orbit. During the return trip crew would enjoy the same artificial gravity as the outbound trip.

During transit to Earth it would be desirable to gradually increase gravity from Mars-g to Earth-g. This gravity transition could be difficult for persons who spent months or years adapting to Mars and then have to reintroduce themselves to the heavier gravity of Earth.

Ionmars · « **Reply #10 on:** 09/19/2022 02:32 pm »

Approaching Earth, dual Starship would reduce its rate of rotation to zero and separate into its two component ships. Inside crew Starship, people would rearrange their in-transit couches to prepare for landing on Earth. This ship would decelerate into the atmosphere through EDL as planned for any Starship returning from a deep space mission.

The accumulator is not designed for EDL; it would (a) be destroyed upon reentry, (b) continue into a disposal orbit towards the sun, or (c) decelerate into LEO for further reuse.

Lampyridae · « **Reply #11 on:** 09/19/2022 03:51 pm »

Some thoughts:

Making use of those (?) existing posts is a great idea.

Starship is designed to handle belly-down or tail-down g-loads. The nose-down orientations would have implications for plumbing, especially the header tanks which are LOC critical.

Short radii are not so bad. Up to 5RPM is tolerable for most, and people will be puking in zero gee anyway.

Not sure the idea of disposing of a "perfectly good Starship" each time would go down well with the colony planners.

My 2 Red Planet cents:

Keep the dorsum-to-dorsum hookup, just keep the Starships as they are. With a spin radius of 9m, 5RPM gets you 0.25g at the bottom line of each Starship, plus you can use two crew Starships with the same hookup method. A connecting tunnel and longer posts enable somewhat longer radii if needed.

Downsides are introducing an intermediate axis, which is an extra pain for stability, and the arrangement of walls/decks is a nightmare.

Ionmars · « **Reply #12 on:** 09/19/2022 04:16 pm »

Quote from: Lampyridae on 09/19/2022 03:51 pm

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...
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Keep the dorsum-to-dorsum hookup, just keep the Starships as they are. With a spin radius of 9m, 5RPM gets you 0.25g at the bottom line of each Starship, plus you can use two crew Starships with the same hookup method. A connecting tunnel and longer posts enable somewhat longer radii if needed.

That might work.
But I think it would be better to have in-transit gravity adjusted for the planet at trip destination (Earth 1.0g; Mars 0.38g). Also, a shorter radius and higher rpm implies greater coriolis effect for crew to deal with.

Greg Hullender · « **Reply #13 on:** 09/19/2022 04:32 pm »

What's the purpose of dragging the depot with you to Mars? Why not just deploy an equivalent weight from a cable attached to the nose of the Starship? Then you can keep the g vector in the same direction as at launch but with a lot less hardware.

Instead of making the weight be a lump of lead, you could make it a storage container filled with things you won't need until you reach Mars. That should be a lot less dead weight than a depot complete with Rapor engines.

Robotbeat · « **Reply #14 on:** 09/19/2022 04:36 pm »

Just do a tether on the nose.

Ionmars · « **Reply #15 on:** 09/19/2022 04:45 pm »

Quote from: Greg Hullender on 09/19/2022 04:32 pm

What's the purpose of dragging the depot with you to Mars? Why not just deploy an equivalent weight from a cable attached to the nose of the Starship? Then you can keep the g vector in the same direction as at launch but with a lot less hardware.

Instead of making the weight be a lump of lead, you could make it a storage container filled with things you won't need until you reach Mars. That should be a lot less dead weight than a depot complete with Rapor engines.

The "dead weight" is the accumulator. It becomes very valuable when inserted into Mars orbit where it will serve as an accumulator for the retirn trip to Earth.

Greg Hullender · « **Reply #16 on:** 09/19/2022 04:46 pm »

Quote from: Ionmars on 09/19/2022 04:45 pm

The "dead weight" is the accumulator. It becomes very valuable when inserted into Mars orbit where it will serve as an accumulator for the retirn trip to Earth.

I could see sending a single depot to Mars (although it doesn't seem to be necessary). I don't see the point of sending one with every single Starship that goes there.

Ionmars · « **Reply #17 on:** 09/19/2022 04:48 pm »

Quote from: Robotbeat on 09/19/2022 04:36 pm

Just do a tether on the nose.

Probably would work.
I just think it would be safer to have the two bodies linked together tightly while rotating in space.

Robotbeat · « **Reply #18 on:** 09/19/2022 04:54 pm »

Why? Being actually docked makes them more susceptible to common failures. On explosion on one may damage both of them.

They could still occasionally meet up and hang out or exchange personnel.

Ionmars · « **Reply #19 on:** 09/19/2022 04:55 pm »

Quote from: Greg Hullender on 09/19/2022 04:46 pm

Quote from: Ionmars on 09/19/2022 04:45 pm
The "dead weight" is the accumulator. It becomes very valuable when inserted into Mars orbit where it will serve as an accumulator for the retirn trip to Earth.
I could see sending a single depot to Mars (although it doesn't seem to be necessary). I don't see the point of sending one with every single Starship that goes there.

Well, there is the goal of reusability.
Accunulator could be reused in Mars orbit to accumulate propellants for a return trip to Earth. After that, If it parks in Earth orbit it could be used again for another trip to Mars, or just as an accumulator in LEO.