Author Topic: ITS as a LEO/VLEO Constellation deployer  (Read 4327 times)

Offline MP99

Re: ITS as a LEO/VLEO Constellation deployer
« Reply #20 on: 04/08/2017 12:13 PM »
ISTM that the drag losses from using wings means the prop would be better used just making the required dV burn directly.

Cheers, Martin

Online Robotbeat

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Re: ITS as a LEO/VLEO Constellation deployer
« Reply #21 on: 04/08/2017 12:42 PM »
ISTM that the drag losses from using wings means the prop would be better used just making the required dV burn directly.

Cheers, Martin
Depends. Hypersonic lift-assisted inclination changes are like up to 40-50% better than pure delta-V.
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Offline MikeAtkinson

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Re: ITS as a LEO/VLEO Constellation deployer
« Reply #22 on: 04/08/2017 02:11 PM »
If the sats are done correctly, they could perform their inclination changes themselves. Since you mentioned VLEO, I'm thinking about 150km or maybe less.

1. Give the birds a winged aerodynamic shape.  You'll need wings anyways to house the solar panels, as a protection against the air.

2. Give the birds an ion engine for station keeping and maneuverability. It should be powerful enough so the birds can climb up from a 140km orbit to higher orbits.

So, the sats are too high for the wings to actually provide lift (the karman line is well below their orbit), but it should be sufficient that they can perform plane changes just by tilting the wings, with the ion engine running to keep the height.

Obviously, the antenna needs to be tiltable too, or should have beam forming capabilities in order to send and receive signals from ground control and from the customers.


Depending on when you want to deploy the constellation, you might not even need a dedicated upper stage (ITS-freighter) to deploy them. Just deploy a few of them every regular tanker flight (50kg per sat means 20 per mt, that doesn't even remotely hurt the tanker). The downside of this method is simple: the tanker needs go dock with the ITS craft, it can't do some fancy inclinations just for a small secondary payload. But the birds can take care of themselves. And the ITS craft needs to be on an orbit that helps with the flight to Mars, everything else would be wasteful.

Adding even a small amount of cost to each satellite is a bad idea as that cost is multiplied by 12000. Aerodynamic  wings and a bigger ion engine will add a fair amount of cost hundreds of millions if not billions extra.

Offline MikeAtkinson

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Re: ITS as a LEO/VLEO Constellation deployer
« Reply #23 on: 04/08/2017 02:16 PM »
But why would you need inclination changes? There are more than enough sats per inclination. They are just on different orbital planes with the same inclination. Drifting between orbital planes is very easy, just adjust the orbital period a little to have a different precession than the rest of the fleet and you are set. Just like sun synchronised orbits.

Exactly, there are relatively few inclinations with lots of satellites in each inclination. For the vLEO sats the drifting to a different orbital plane cannot take too long because of the limited lifetime of the satellites, but a few weeks is probably OK as it will take that long to check out and commission them

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Re: ITS as a LEO/VLEO Constellation deployer
« Reply #24 on: 04/08/2017 03:24 PM »
But you cannot launch to a near polar orbit from Florida without an inclination change and/or huge dogleg. The ability to change inclinations means they don't need a West Coast launch site for ITS.
« Last Edit: 04/08/2017 03:26 PM by Robotbeat »
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Offline DanielW

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Re: ITS as a LEO/VLEO Constellation deployer
« Reply #25 on: 04/08/2017 11:55 PM »
But you cannot launch to a near polar orbit from Florida without an inclination change and/or huge dogleg. The ability to change inclinations means they don't need a West Coast launch site for ITS.
But what percentage of the constellation needs to be high inclination? Falcon Heavy could handle those from Vandenberg.

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Re: ITS as a LEO/VLEO Constellation deployer
« Reply #26 on: 04/09/2017 12:30 AM »
But you cannot launch to a near polar orbit from Florida without an inclination change and/or huge dogleg. The ability to change inclinations means they don't need a West Coast launch site for ITS.
But what percentage of the constellation needs to be high inclination? Falcon Heavy could handle those from Vandenberg.
Probably hundreds of satellites. Either way, that means you need to keep Falcon Heavy around or be happy with a LOT of F9 flights, plus a probably-unrecoverable satellite deployer. Plus another site to process the satellites.

Again, ITS /will/ have the capability to change inclination relatively efficiently just due to the fact it is a lifting body. And if it succeeds, it'll be much cheaper to launch than even a fully reused Falcon Heavy. There's no real good reason /not/ to use this capability to reach high inclinations
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Offline ZachF

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Re: ITS as a LEO/VLEO Constellation deployer
« Reply #27 on: 04/11/2017 05:17 PM »
I think ITS will eventually be used to upkeep the Constellation. Even if there is a ceiling for the number of satellites it can carry, an ITS could allow the next-gen constellation sats to be much larger and more powerful.

Offline MP99

Re: ITS as a LEO/VLEO Constellation deployer
« Reply #28 on: 04/11/2017 05:51 PM »


ISTM that the drag losses from using wings means the prop would be better used just making the required dV burn directly.

Cheers, Martin
Depends. Hypersonic lift-assisted inclination changes are like up to 40-50% better than pure delta-V.

OK, sometimes intuition doesn't serve well.

That sounds like a useful fuel saving.

Cheers, Martin


Offline meekGee

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Re: ITS as a LEO/VLEO Constellation deployer
« Reply #29 on: 05/14/2017 05:11 PM »
Bump - In an interview Tom Mueller made the link between ITS and sat launching, though not quite as explicit as "ITS will launch this constellation"
« Last Edit: 05/14/2017 08:51 PM by meekGee »
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