Author Topic: SpaceX Sign 18 spacecraft deal with ORBCOMM  (Read 122060 times)

Offline Danderman

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Re: SpaceX Sign 18 spacecraft deal with ORBCOMM
« Reply #20 on: 09/04/2009 06:49 am »
FYI, the existing satellites are in ~700 km circular orbits at 45 degrees inclination. The Falcon 1 user's guide says the performance to that orbit should be about 750 kilograms.

The satellite manufacturer (see Skyrocket's link above) says the satellites' propulsion system is hydrazine powered, so presumably they have some ability to maneuver, if limited.

I'd speculate that the satellites will be stacked, similar to how prior versions were (see here), and separated by spring pushers or some similarly simple mechanism. At the appropriate intervals, each could make a small orbit raising burn to assume sufficient separation from the previous satellite. Doing so with minimal fuel burn could take a while, but it's feasible.

The above almost describes the most reasonable mission architecture, but there are some details left out. Most importantly, the Falcon 1E at this time does not have the capability of injecting 6 different objects into the different required portions of the orbital plane, so a different strategy must be used. Fortunately, the reason why the satellites have a mass 100 kg greater than the 1st generation is due to their active propulsion system ... which provides the answer to everyone's question. What will happen is that that Falcon 1E will put all 6 payloads into a 400 or 500 km orbit, at 45 degrees. Each satellite will put itself into the final 700 km orbit when their low orbit drifts to the required position for the satellite to get into its final position. Globalstar does the same thing, they are put into a transitional 900 km orbit, and then inject themselves into the final 1400 km orbit.

So ... all Falcon 1E need do is put 6 142 kg satellites into a 500 km orbit at 45 degrees.

Offline Skyrocket

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Re: SpaceX Sign 18 spacecraft deal with ORBCOMM
« Reply #21 on: 09/04/2009 08:31 am »
FYI, the existing satellites are in ~700 km circular orbits at 45 degrees inclination. The Falcon 1 user's guide says the performance to that orbit should be about 750 kilograms.

The satellite manufacturer (see Skyrocket's link above) says the satellites' propulsion system is hydrazine powered, so presumably they have some ability to maneuver, if limited.

I'd speculate that the satellites will be stacked, similar to how prior versions were (see here), and separated by spring pushers or some similarly simple mechanism. At the appropriate intervals, each could make a small orbit raising burn to assume sufficient separation from the previous satellite. Doing so with minimal fuel burn could take a while, but it's feasible.

The above almost describes the most reasonable mission architecture, but there are some details left out. Most importantly, the Falcon 1E at this time does not have the capability of injecting 6 different objects into the different required portions of the orbital plane, so a different strategy must be used. Fortunately, the reason why the satellites have a mass 100 kg greater than the 1st generation is due to their active propulsion system ... which provides the answer to everyone's question. What will happen is that that Falcon 1E will put all 6 payloads into a 400 or 500 km orbit, at 45 degrees. Each satellite will put itself into the final 700 km orbit when their low orbit drifts to the required position for the satellite to get into its final position. Globalstar does the same thing, they are put into a transitional 900 km orbit, and then inject themselves into the final 1400 km orbit.

So ... all Falcon 1E need do is put 6 142 kg satellites into a 500 km orbit at 45 degrees.


For an interim 500 km / 45° orbit the F1e payload capacity is according to the users guide 850 kg, which could be just enough for 6 satellites, provided there are no performance shortfalls in F1e. I don't know, if the given payload capability includes the mass for the payload adaptor.

Offline robertross

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Re: SpaceX Sign 18 spacecraft deal with ORBCOMM
« Reply #22 on: 09/04/2009 01:16 pm »
I wonder if it's worth SpaceX's while to launch incrementally: only 1 or 2 satellites first (to be on the safe side), then 3-4, then go with a deploy of 6 at once. Yes it costs more, but if there were a failure you don't lose all 6 sats at once.

Of course the flip side is the customer (and others) seeing this approach would make them wonder if SpaceX is confident in their launcher. Damned if you do...damned if you don't.

Offline kevin-rf

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Re: SpaceX Sign 18 spacecraft deal with ORBCOMM
« Reply #23 on: 09/04/2009 02:14 pm »

Or if ORBCOMM was smart, sign a fixed price agreement that says X dolars for X Sats delivered to the correct orbit and it is up to SpaceX to figure out how many F1e flights it will take.

btw. We seem to have two threads going on about this, maybe the mod's that be should merge em.
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Offline Danderman

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Re: SpaceX Sign 18 spacecraft deal with ORBCOMM
« Reply #24 on: 09/04/2009 02:53 pm »
For an interim 500 km / 45° orbit the F1e payload capacity is according to the users guide 850 kg, which could be just enough for 6 satellites, provided there are no performance shortfalls in F1e. I don't know, if the given payload capability includes the mass for the payload adaptor.

For deployment into a satellite plane, the greater the difference in altitude between the parking orbit and the final orbit, the more quickly the satellites can be injected into the final orbit after launch. So, a 500 km parking orbit is not the best choice, given a 700 km final orbit. A 400 km parking orbit would allow for a shorter parking period, and from a 400 km, the prop usage, assuming a 250 sec ISP, would be about 10 kg, not a large penalty, for the injection into the final orbit. The big issue would be the increased drag at 400 km, compared with 500 km. I would look for a parking orbit at least 400 km high, maybe not as high as 500 km.

Also, at that low altitude, SpaceX will probably have to de-orbit the last stage, so some  mass should be allocated to the final burn.

« Last Edit: 09/04/2009 02:54 pm by Danderman »

Offline cixelsyD

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Re: SpaceX Sign 18 spacecraft deal with ORBCOMM
« Reply #25 on: 09/04/2009 02:57 pm »
Does anyone know the volume of these Satellites. Could it be that volume would be more of a restriction than mass?

Offline robertross

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Re: SpaceX Sign 18 spacecraft deal with ORBCOMM
« Reply #26 on: 09/04/2009 03:01 pm »
Chris started this topic on the SpaceX thread as well...

http://forum.nasaspaceflight.com/index.php?topic=9958.msg471517#msg471517

Offline Ben the Space Brit

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Re: SpaceX Sign 18 spacecraft deal with ORBCOMM
« Reply #27 on: 09/04/2009 03:15 pm »
Does anyone know the volume of these Satellites. Could it be that volume would be more of a restriction than mass?

Stowed for launch, they're 1x1x1m cubes, so a Falcon-1e could carry quite a few without problems.
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Re: SpaceX Sign 18 spacecraft deal with ORBCOMM
« Reply #28 on: 09/04/2009 04:16 pm »
Why the heck doesn't the press release state the number of launches?  It's kinda weird to leave that detail out.

Offline Chris Bergin

Re: SpaceX Sign 18 spacecraft deal with ORBCOMM
« Reply #29 on: 09/04/2009 04:23 pm »
Why the heck doesn't the press release state the number of launches?  It's kinda weird to leave that detail out.

Agreed, that caught me out at first - as I misread this as 18 launches....

I'll send off a request, given SpaceX are usually chatty about their positive news.
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Offline iamlucky13

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Re: SpaceX Sign 18 spacecraft deal with ORBCOMM
« Reply #30 on: 09/04/2009 05:57 pm »
Does anyone know the volume of these Satellites. Could it be that volume would be more of a restriction than mass?

Stowed for launch, they're 1x1x1m cubes, so a Falcon-1e could carry quite a few without problems.

More precisely from here:
http://www.microsatsystems.com/files/en/user/cms/OG2_8_08.pdf

Bus Stowed Dimensions - 1.0m (W) x 0.6m (H) x 0.9m (D)

The illustration looks like a rectangular bus with a 3 panel solar array unfolding out one side, and a big telescoping antenna out the other.

The Falcon 1e payload dynamic envelop is 1.55m in diameter x 3.8m height, but a 4.1 m radius curve starts 1.7 meters up.

Doing some napkin geometry, it looks like the corner of a symmetrical payload stack would meet the fairing 2.6 meters up. That equates to the depth of 4.3 satellites. With fancy stacking, which may not be friendly to the satellites, I think there's room for at most five of them.

So good call on the possible volume limitation. It looks like a minimum of five launches.

Why the heck doesn't the press release state the number of launches?  It's kinda weird to leave that detail out.

Yeah, weird. Certainly that was agreed upon before signing.

I can't really imagine the customer would want that information kept secret, either.

Offline yinzer

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Re: SpaceX Sign 18 spacecraft deal with ORBCOMM
« Reply #31 on: 09/04/2009 06:58 pm »
Why the heck doesn't the press release state the number of launches?  It's kinda weird to leave that detail out.

Yeah, weird. Certainly that was agreed upon before signing.

I can't really imagine the customer would want that information kept secret, either.

Someone said that when they asked Gwynne Shotwell how many launches were involved, she said "as many as it takes."  So it might be that the contract involves free reflights in the case of failure, or maybe even free reflights and compensation for the lost satellites.

SpaceX has always claimed they offered low but fixed prices, on a take-it-or-leave-it basis.  You could imagine that they might not want to advertise that they were now open to negotiation.

Or it could be something completely different.
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Offline daver

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Re: SpaceX Sign 18 spacecraft deal with ORBCOMM
« Reply #32 on: 09/05/2009 12:39 am »
Would it be better to,

A: launch 3 at a time and recover the stage?
B: launch 4 and throw the rocket away?

(A) Could be good practice for stage recovery or (B) Could be a good way to make money. 
  It should be an interesting choice.

Offline Skyrocket

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Re: SpaceX Sign 18 spacecraft deal with ORBCOMM
« Reply #33 on: 09/05/2009 05:25 am »
Originally planned the satellites were to  be launched 6 at a time, which is a strong hint, that the OG2 constellation will feature 3 orbital planes each with 6 satellites.
Therfore the launch of 3 sats on each F1e is the most likely choice to distribute the 18 sats on the 3 orbital planes.

Offline ugordan

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Re: SpaceX Sign 18 spacecraft deal with ORBCOMM
« Reply #34 on: 09/05/2009 11:00 am »
Yeah, weird. Certainly that was agreed upon before signing.

Is it really so unlikely that they simply don't know exactly how many launches they'll need at this point? Say they understand it'll be somewhere on the order of 5 +/- 1 launches, but the exact number would depend on F1e demonstrated performance. That could also explain why the value of the contract wasn't released.

SpaceX added ORBCOMM to their manifest, but simply put 2010-2014 as a placeholder, no breakdown per launch.

Offline simon-th

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Re: SpaceX Sign 18 spacecraft deal with ORBCOMM
« Reply #35 on: 09/05/2009 11:27 am »
Yeah, weird. Certainly that was agreed upon before signing.

Is it really so unlikely that they simply don't know exactly how many launches they'll need at this point? Say they understand it'll be somewhere on the order of 5 +/- 1 launches, but the exact number would depend on F1e demonstrated performance. That could also explain why the value of the contract wasn't released.

SpaceX added ORBCOMM to their manifest, but simply put 2010-2014 as a placeholder, no breakdown per launch.

If they require 6 F1e launches for their 18 sats, it would have been much more practical to just purchase 2 Rokots (1950kg to LEO) for a lot less money.

It has to be a 3-launch scenario - maximum 4 launches.

Offline Skyrocket

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Re: SpaceX Sign 18 spacecraft deal with ORBCOMM
« Reply #36 on: 09/05/2009 11:44 am »
Yeah, weird. Certainly that was agreed upon before signing.

Is it really so unlikely that they simply don't know exactly how many launches they'll need at this point? Say they understand it'll be somewhere on the order of 5 +/- 1 launches, but the exact number would depend on F1e demonstrated performance. That could also explain why the value of the contract wasn't released.

SpaceX added ORBCOMM to their manifest, but simply put 2010-2014 as a placeholder, no breakdown per launch.

If they require 6 F1e launches for their 18 sats, it would have been much more practical to just purchase 2 Rokots (1950kg to LEO) for a lot less money.

It has to be a 3-launch scenario - maximum 4 launches.

To launch the 18 satellites into 3 orbital planes it would have required 3 Rokots.

Offline ugordan

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Re: SpaceX Sign 18 spacecraft deal with ORBCOMM
« Reply #37 on: 09/05/2009 11:59 am »
To launch the 18 satellites into 3 orbital planes it would have required 3 Rokots.

What about using nodal regression to move different sats from a single launch to different planes? Is that feasible or too complicated in addition to trying to separate the satellites in a single plane?

Offline William Barton

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Re: SpaceX Sign 18 spacecraft deal with ORBCOMM
« Reply #38 on: 09/05/2009 12:04 pm »
At this point in the evolution of SpaceX as a company, these things may simply not matter. The cost of Falcon 1e is likely to be small enough SpaceX might simply have made a competitive bid, knowing they might have to write off the "profit." What if it takes 18 launches? How much will SpaceX "lose" on the deal? And how much will they gain down the road by successfully completing the contract? As long as they don't experience an embarrassing series of launch failures, it's a win for them.

Offline ugordan

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Re: SpaceX Sign 18 spacecraft deal with ORBCOMM
« Reply #39 on: 09/05/2009 12:07 pm »
What if it takes 18 launches? How much will SpaceX "lose" on the deal?

Depends. How much does production of a single Falcon 1e cost them even neglecting sunk development cost? How much does range support for launch cost them? It doesn't sound like peanuts to me.

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