CRS Program Update

Cygnus Spacecraft
Cygnus Cargo Spacecraft Photo Credit: AmericaSpace

KENNEDY SPACE CENTER, FL – Under the Under NASA’s Commercial Resupply Services (CRS) contract, Orbital Sciences[1][2] and SpaceX[3][4] are each to be paid $1.6 billion to deliver 20 metric tons, or 44,100 lbs, of cargo to the International Space Station (ISS). Under the terms of CRS, SpaceX will conduct 12 missions and Orbital Sciences will launch 8 missions. As Orbital Sciences is on its first demo mission to ISS, this is a good time to review the status of the CRS program.

SpaceX has conducted one demo and two CRS missions to ISS. SpaceX’s COTS Demo 2/3 mission lifted-off on May 22, 2012, CRS–1, or SpX–1, on October 11, 2012, and CRS–2 on March 1, 2013. SpX–3 is not expected until mid-January 2014. Total delivered upmass by SpaceX to ISS to date, without packaging, is 1,519 kg (3,349 lbs).

Orbital Sciences is currently conducting its first demo flight of Orbital’s Cygnus robotic cargo spacecraft, which will rendezvous with, and then be captured by, ISS. Orbital’s first CRS–1 flight is scheduled for December 8, roughly 2 1/2 months from now, and will carry 1,288 kg (2,839 lbs) of supplies, not counting packaging, to ISS. Over the course of its CRS contract, Orbital will deliver on average 2,500 kg to the ISS over its 8 missions.

Company Mission Launch Date Unpackaged Cargo
Upmass (kg/lbs) Downmass (kg/lbs)
SpaceX COTS Demo[5] 22 May 2012 520/1,146 660/1,455
SpaceX SpX–1[6] 8 October 2012 454/1,001 520/1,146
SpaceX SpX–2[7] 1 March 2013 545/1,202 1,045/2,303
Orbital Sciences COTS Demo 18 September 2013 700/1,543 1,124/2,478
Orbital Sciences Orb–1 8 December 2013 1,288/2,839 956/2,107
Orbital Sciences Orb–2 8 May 2014 1,563/3,446 1,563/3,446

The Dragon spacecraft weighs 4,200 kg (9,259 lbs) and can handle 3,310 kg (7,297 lbs) in both its shirt-sleeve pressurized volume and its unpressurized trunk for a total of 6,620 kg (14,595 lbs). The first generation OSC Cygnus spacecraft weights 1,500 kg (3,300 lbs) and the second generation Cygnus + that will be used after its the third Orbital Sciences CRS mission, Obs–3, weights 1,800 kg (4,000 lbs). Below is a table of pressurized volume and payload upmass capabilities of ISS resupply spacecraft.

Spacecraft Pressurized Volume Pressurized Payload
m^3 ft^3 kg lbs
Progress 7.6 268.00 2,350.00 5,200.00
Dragon[8] 11.00 353.00 3,310.00 7,297.30
Cygnus[9] 18.90 670.00 2,000.00 4,400.00
Cygnus + 27.00 950.00 2,700.00 6,000.00
ESA ATV 48.00 1,695.10 7,667.00 16,900.00

SpaceX’s CRS missions’ past payload upmass to date of 1,519 kg (3,349 lbs) means that future missions will need to be more heavily loaded. Certainly from its payload mass numbers, Dragon is up to the task. The Dragon’s pressurized volume of 11 m3 (388 ft3)[10], 1 m3 more than the 1960’s era Apollo command module. From SpX-3 going forward, in order to fulfill the terms of its fixed-price CRS contract for the remainder of its term, SpaceX must deliver a total of almost 18,000 kg (roughly 41,000 lbs) to ISS. This means that the average Dragon payload mass will need to be around 1,800 kg (4,000 lbs) and would represent a significant increase in payload over past SpaceX CRS missions, though clearly not an amount that comes even close to Dragon’s payload capability.

As noted above, Orbital Sciences will also have a challenging time meeting the payload commitments of its CRS contract after Obs-2. From Obs-3 onward, Orbital Sciences will need to deliver around 15,500 kg (33,000 lbs) to ISS. This means that over the next six Orbital Sciences CRS missions, Cygnus must launch an average of 2,500 kg (5,500 lbs). While the standard Cygnus only carries 2,000 kg (4,409 lbs), the Cygnus +, which will see its debut beginning on Obs-3, has just the right amount of payload capacity of 2,700 kg (5,950 lbs).

After As a historical benchmark, Shuttle could easily lift 9 metric tons (20,000 lbs) to ISS, although it was, after introduction of the Al-Li 2195 external tank [11], capable of lofting nearly 13 metric tons (28,000 lbs) while maintaining its abort landing capability.

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  1. “KENNEDY SPACE CENTER, FL – Under the Under NASA’s Commercial Resupply Services (CRS) contract, Orbital Sciences[1][2] and SpaceX[3][4] are each to be paid $1.6 billion to deliver 20 metric tons, or 44,100 lbs, of cargo to the International Space Station (ISS”

    I thought the CRS contract was for 3.5 billion and that SpaceX received 1.6 billion for 12 launches and Orbital received 1.9 billion for 8 launches..

    So Orbital got 300 million more for 4 fewer launches and no down cargo.

    • Once the gov’t shutdown is over and the JSC CRS contract site is back up, read the contracts of both Orbital and SpaceX. You will find that Orbital has, just like SpaceX, an up-mass and a down-mass CRS requirement, both of which are larger than SpaceX’s; fixed-price of 20 mt for $1.6 billion. I am not sure where you get $3.5 billion. So both companies are being paid the same to launch the same total up-mass. Orbital Sciences is being paid for fewer launches because Cygnus has a larger payload volume and will be able to launch its required 20 mt in fewer launches.

      The problem for Dragon is payload density and its 11 m3 pressurized volume. Dragon can launch more payload mass, but it’s pressurized volume is much smaller than that of Cygnus (61%) and Cygnus+ (41%). If you look at the second chart, you’ll see that the Cygnus Demo mission carried more up-mass (545 kg vs. 700 kg) to, and down-mass (1,045 kg vs 1,124 kg) from, ISS than any Dragon mission to date. It’s not a criticism of Dragon, just a fact. Look again at the Cygnus Demo payload mass, compare that to any of the Dragon CRS missions, and you’ll see what I mean.

      Like the ESA’s ATV, Orbital’s down-mass burns-up in reentry. After all, ISS, like any human outpost, creates trash. Reentry is one environmental way to get rid of the trash.

  2. I stand corrected as to the value of Orbital Sciences CRS contract.

    But while I stand corrected on Orbital’s award amount, I think you’re mistaken in your confusion of down mass with mass returned to Earth intact. Look again at the numbers for down mass and you’ll see that Orbital’s down mass exceeds SpaceX’s by a substantial amount. By SpX2 a total of 2,225 kg (4,905 lbs) will be down massed. By Obs-2 a total of 3,643 kg (8,031 lbs) will be down massed.

    In summary, Orbital Sciences will in only its second CRS mission have down massed 1,418 kg (3,126 lbs) more than SpaceX.

    One reason Orbital’s contract may be lower is that Orbital, on top of more down mass, requires less mission support from NASA (8 vs 12 missions). Something to think about.

  3. So is disposal of trash worth more than returning useful cargo such as blood samples, equipment to be refurbished and reused, etc? SpaceX should be paid more since they provide a greater capability.

    • First, you’d have to ask NASA why Orbital Sciences is paid more than SpaceX for fewer supply launches to ISS. I assume you’re a fan of commercial space, so I’m not sure why you even care. Or are you simply a fan of commercial space when SpaceX is the contractor?

      Maybe Orbital gets more because Cygnus has nearly twice, and will soon have nearly three times, the pressurized volume of Dragon and is therefore able to haul more cargo volume and larger cargo items. True, Dragon can handle more cargo mass than Cygnus. In this case payload density, not simply mass, of cargo may be the capability NASA is willing to pay more for.

      Your point about equipment being returned makes some mistaken assumptions about the cost-benefit of returning, repairing, and then relaunching equipment to ISS. After all, SpaceX has yet to reuse a Dragon for good reasons. There is some value in looking at failed equipment. But it would have to be a very special piece of equipment indeed that is cheaper to pay reentry and repair cost than to just build and launch it.

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