Author Topic: ITS Ships Flying As a Group  (Read 3165 times)

Offline Aussie_Space_Nut

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Re: ITS Ships Flying As a Group
« Reply #20 on: 06/25/2017 02:00 AM »
Ok. So you would need some expenditure of fuel to stabilise the orbit.

However if the squadron arrived at roughly the same time but each chose to aerobrake such that they all exited Mars atmosphere at slightly different speeds you would end up with different elliptical orbits for each ship thereby allowing different landing times for each ship. Little to no fuel required.

Offline guckyfan

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Re: ITS Ships Flying As a Group
« Reply #21 on: 06/25/2017 05:05 AM »
You'd need, at a minimum, to do enough of a burn at apogee to raise the perigee above the atmosphere.

No need to get into a stable orbit. You can land on the next pass. Expend a little propellant for precision targeting of the landing area.

But I doubt this will happen with passenger ships. They may need to do two passes for the heaviest cargo with 450t because they can not bleed enough speed in one pass, being that heavy.

Offline Aussie_Space_Nut

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Re: ITS Ships Flying As a Group
« Reply #22 on: 06/25/2017 05:38 AM »
So, bottom line is a squadron of ITS ships arriving together can land at different times by choosing to aerobrake into slightly different elliptical orbits.  :)

Offline Kaputnik

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Re: ITS Ships Flying As a Group
« Reply #23 on: 06/25/2017 11:12 AM »
So, bottom line is a squadron of ITS ships arriving together can land at different times by choosing to aerobrake into slightly different elliptical orbits.  :)

I know SpaceX are good at doing the things that nobody has done before, but I still feel the need to point out that aerocapture is indeed one of the things that nobody has done before.
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Online philw1776

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Re: ITS Ships Flying As a Group
« Reply #24 on: 06/25/2017 01:40 PM »
Even if all ITS departed "together" slight deltaV differences and/or departure times could adjust landing times by hours or even days.  No need for complex failure inviting aeromanovering operations at Mars to get differing landing times. 
The ability to get from ship to ship in an emergency would be longer in this scenario.
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Offline Hotblack Desiato

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Re: ITS Ships Flying As a Group
« Reply #25 on: 06/27/2017 04:42 PM »
I could imagine, that the ITS-crafts can be in LEO 10km apart on the same orbit. That would be a bit over a second time between each other.

When they fire up the engines for the TMI-burn they will then stay 10km apart after the burn.

This would then raise the question, whether they can dock to each other on the interplanetary flight or not. I don't see a reason why they should, but just the possibility to do so adds another layer of security, since one ITS in distress can be supported by the others, either by providing spare parts or by rescuing the crew and abandoning the craft. If they fly further apart, a mid-flight docking might not be possible.

Another advantage is, that people will tend to communicate with each other, and such a close distance means, that the signal delay is virtually irrelevant.

During reentry, they should have at least 10km distance between two crafts. This will cause other problems, such as we don't know the cross range capability of ITS inside the martian atmosphere. I wouldn't assume more than 50km cross range, which clearly limits their number of ITS landing on the same spot on the same day.

I don't fear that one ITS might blow up during reentry. The problem we should consider is the collision of two ITS during reentry and landing.

Offline launchwatcher

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Re: ITS Ships Flying As a Group
« Reply #26 on: 06/27/2017 06:19 PM »
I could imagine, that the ITS-crafts can be in LEO 10km apart on the same orbit. That would be a bit over a second time between each other.

When they fire up the engines for the TMI-burn they will then stay 10km apart after the burn.

They'll keep the same spacing in time, not in space.   Immediately after the TMI burn they'll be moving faster than they were in LEO so they'll have to be more than 10km apart to keep the same time separation.

Offline Hotblack Desiato

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Re: ITS Ships Flying As a Group
« Reply #27 on: 06/27/2017 08:33 PM »
I could imagine, that the ITS-crafts can be in LEO 10km apart on the same orbit. That would be a bit over a second time between each other.

When they fire up the engines for the TMI-burn they will then stay 10km apart after the burn.

They'll keep the same spacing in time, not in space.   Immediately after the TMI burn they'll be moving faster than they were in LEO so they'll have to be more than 10km apart to keep the same time separation.


True, after accelerating, the ITS-crafts should spread to 15-20km (maybe more, maybe not exactly the same trajectories, which makes correction burns necessary). But those are easily manageable distances, if one ITS needs repair or an evacuation. Accelerate 1 m/s towards another ITS, and 4h later, you're there. They even could fly within a few hundred meters to each other, the only thing they should take care of: don't bump into each other.

Offline CraigLieb

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Re: ITS Ships Flying As a Group
« Reply #28 on: 06/28/2017 02:25 PM »
It would make sense that here would be small shuttles for essential exchange both in orbit prior to departure and once on the way to Mars. One might speculate that emergency repairs outside the ship while underway may demand these kinds of EVA beyond just a suit especially if large (mass/inertia/bulky) repair parts have to be taken along.   Dragon docking maneuvers experience is critical here.
The rocket scientists can figure out the delta-V requirements to move between ships in orbit. Suggest they not let the ship board computer control the pod bay doors.
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