SpaceX Falcon 9/Dragon CRS SpX-1 MISSION GENERAL DISCUSSION

[subzero788]

I seem to recall that Falcon 9 1.0 only gets about 10k kg to LEO, including the dragon module. It's hard to find recent numbers, but figure about 4.2k kg dry mass for the dragon, 454 kg for the payload, up to 1200 kg of fuel for the dragon (who knows how full it needs to be), 124 kg + payload adapter + any booster per orbcomm bird. That's about 5.5-6k kg there; still a lot of margin, but not 2/3rds.

-R C

Falcon 9 1.0 was supposed to be about 10mt to LEO, but that was for around ~200km, 28.5 inclination, vs 400 km, 56.1 inclination of the ISS.
Besides, I don't believe Falcon 9 achieved that predicted performance.

[grythumn]

I seem to recall that Falcon 9 1.0 only gets about 10k kg to LEO, including the dragon module. It's hard to find recent numbers, but figure about 4.2k kg dry mass for the dragon, 454 kg for the payload, up to 1200 kg of fuel for the dragon (who knows how full it needs to be), 124 kg + payload adapter + any booster per orbcomm bird. That's about 5.5-6k kg there; still a lot of margin, but not 2/3rds.

-R C

Falcon 9 1.0 was supposed to be about 10mt to LEO, but that was for around ~200km, 28.5 inclination, vs 400 km, 56.1 inclination of the ISS.
Besides, I don't believe Falcon 9 achieved that predicted performance.

Yeah, I was looking for that NASA pdf with better performance numbers and graphs and I couldn't find it, so I ended up trying to dig up what I could online. Should've known better.

-Bob

[grythumn]

I seem to recall that Falcon 9 1.0 only gets about 10k kg to LEO, including the dragon module.

not with dragon

The 10mt (or whatever the actual performance of the falcon 9 1.0 to ISS orbit; I don't have better numbers but I know that is too high) payload has to include the dragon... it doesn't ride up for free. 4mt or so for the dragon itself, another mt or so for fuel, leaving at most 5mt for cargo, likely significantly less. nyet?

-R C

[ugordan]

Falcon 9 1.0 was supposed to be about 10mt to LEO

The F9 User Guide published January 2009 states that 10 tonnes was the Block 2 target so it's clear that 1.0 was known to have lower performance than that long before it actually flew. Whether 1.0 subsequently fell short of its own performance goals and by how much, I have no idea, but it's more complicated than saying that 1.0 was supposed to be 10 mt to LEO. Perhaps originally when the vehicle was first unveiled that was the case.

FWIW, the NASA ELV page shows about 9 tonnes to LEO for v1.0. Whether that itself is up to date, I don't know since that would have been based on two flights only, one with roll issues and another with a truncated MVac nozzle.

[Rocket Guy]

I presume that the launch windows for ISS rendezvous move steadily throughout the year.  How long will it be before they are launching CRS missions in the day-time again?

Launch time, same as shuttle, gets 23-25 minutes earlier each day. About 8:34pm Oct 7, 8:12pm Oct 8, 7:45pm Oct 9, etc. Every 60 days approximately it returns back to the same time again.

Sunset is right around 7:00pm at that time.

[Salo]

http://elvperf.ksc.nasa.gov/elvMap/staticPages/launch_vehicle_info1.html

[grythumn]

http://elvperf.ksc.nasa.gov/elvMap/staticPages/launch_vehicle_info1.html

That was what I was remembering and couldn't find. Thank you! So about 8.1mt gross payload to ISS orbit for F9 1.0, and about 15mt gross for F9 1.1 for the same.

-R C

[Salo]

about 15mt gross for F9 1.1 for the same.

Mass to Low Earth Orbit (LEO):    13,150 kg (29,000 lb)
Inclination:    28.5 degree

http://www.spacex.com/falcon9.php

[Robotbeat]

about 15mt gross for F9 1.1 for the same.

Mass to Low Earth Orbit (LEO):    13,150 kg (29,000 lb)
Inclination:    28.5 degree

http://www.spacex.com/falcon9.php

Isn't the same as other figures that are used, such as what NASA uses for mission-planning (NLS II). Ironically, the SpaceX.com figures are /lower/ than the ones NASA uses for Falcon 9 v1.1. Why that is exactly is up for debate, but I tend to give more credence to NASA's numbers (which are up for more scrutiny).

It's possible, for instance, that SpaceX is planning on having small secondaries on /every single non-NASA flight/ unless a premium (i.e. above the posted cost) is charged. This may help them hit their rather tight per-launch cost figures.

[vigleik]

Isn't the same as other figures that are used, such as what NASA uses for mission-planning (NLS II). Ironically, the SpaceX.com figures are /lower/ than the ones NASA uses for Falcon 9 v1.1. Why that is exactly is up for debate, but I tend to give more credence to NASA's numbers (which are up for more scrutiny).

Engine out capability? That would also explain the low SpX-1 payload; starting from Nasa's 8.6t number and subtracting an appropriate amount for engine out only leaves about that much after accounting for the dragon dry mass and fuel.

[stone]

The very low cargo mass (500kg) which is roughly 15% of what is possible makes me wonder. They have to transport avg. 1700kg to get 20000kg to the station in 12 flights. Is it possible that the fueled capsule + 500kg is the max mass they get to LEO? This would mean that only V.1.1 will get them to the point were Dragon makes sense. I do not belief the numbers for LEO of the Falcon9 V1.0 published, sorry.   

[ugordan]

Is it possible that the fueled capsule + 500kg is the max mass they get to LEO?

I wonder about actual margins as well, but consider that they're flying an Orbcomm satellite on this flight as well. AFAIK that requires a 2nd stage restart to about a 700 km apogee. That's bound to account for a couple of hundred kg (WAG) of mass reallocated from Dragon payload to F9 propellant load.

I do not belief the numbers for LEO of the Falcon9 V1.0 published, sorry.

And you would believe anything anyone says over here if it's not what you're expecting to hear? Why ask these questions in the first place, then?

[stone]

I do not believe the numbers for LEO of the Falcon9 V1.0 published, sorry.

And you would believe anything anyone says over here if it's not what you're expecting to hear? Why ask these questions in the first place, then?
[/quote]

I would believe when somebody points out that there is a second payload,  a design change, the necessity to transport helium balloons  for a birthday party, the NASA requirement that they reach orbit with only 7 Merlins running .....

But with the published numbers for LEO and the payload one number is wrong and this is not the payload number.

So I miss a good explanation.

The 700km for the secondary payload is partly what I searched for.

[Ben the Space Brit]

Stone does make a good point.  Has anyone calculated what the ORBCOMM payload and its orbital insertion requirements will be cutting off of Dragon's theoretical maximum payload to ISS? That might explain the relatively low NASA payload

[subzero788]

Another reason could simply be that the cargo going up on this flight has a large volume to weight ratio

[MP99]

... That might explain the relatively low NASA payload

It reads like a lot of the load is science racks. Does that further mass limit the payload?

Not racks but contents of racks, which is not mass limiting

I take Jim's comment to mean that Dragon is volume-limited for this cargo. AIUI, Dragon needs a very dense cargo to carry it's max pressurised payload.

cheers, Martin

[stone]

If they need dense cargo how do they meet the 20000kg in 12 flights requirement?

The point is where is the extra lift capability of V1.1 going? If it is not needed for CRS missions why should they use it?

So I do not believe that the V1.0 has the capability to lift a fully loaded Dragon. This is why the V1.1 has to be developed.

Everything will clear up when the payload of the first CRS  with V1.1 is announced.

[MP99]

If they need dense cargo how do they meet the 20000kg in 12 flights requirement?

Unpressurised cargo in the trunk?

The point is where is the extra lift capability of V1.1 going? If it is not needed for CRS missions why should they use it?

So I do not believe that the V1.0 has the capability to lift a fully loaded Dragon. This is why the V1.1 has to be developed.

NASA are paying for this flight. The Orbcomm sat wouldn't be on there as a secondary if they were limited by the F9, or NASA could get in more payload.

cheers, Martin

[Joffan]

AFAIK, the ISS is not short of supplies. I do not regard this Dragon flight as a critical supply run, just a top-up, but I can see two important things NASA might be trying to achieve with this flight:
1. Establish their own supply chain independent of other countries, whether there is an urgent need or not
2. Get downmass capacity. SpX-1 will be carrying MORE downmass than it did upmass.

[Jim]

AFAIK, the ISS is not short of supplies. I do not regard this Dragon flight as a critical supply run,

It is for experiments