Author Topic: Dragon 2 dry mass and dV (Read 13326 times)

whitelancer64 · « **on:** 03/08/2021 06:24 pm »

Just wondering if anyone out there has a source for the Dragon 2 dry mass and dV.

I've seen a lot of estimates (here, on reddit, etc.) that the dV is around 350-400 m/s

I've seen a post here that give the dry mass as "Dragon 2 Dry Mass: 6750 kg"

https://forum.nasaspaceflight.com/index.php?topic=42363.msg1652528#msg1652528

Just looking for a good source to verify these.

gongora · « **Reply #1 on:** 03/08/2021 06:55 pm »

I don't think I've seen dry mass or launch mass for Dragon 2. We got a mass as it left the Station one time, and we've seen propellant amounts in environmental docs.

whitelancer64 · « **Reply #2 on:** 03/08/2021 08:38 pm »

Right, we got the wet mass given by NASA for two points in the Dragon Crew Demo flight.

https://www.nasa.gov/feature/top-10-things-to-know-for-nasa-s-spacex-demo-2-return

"At the time of undock, Dragon Endeavour and its trunk weigh approximately 27,600 pounds [12,520 kg].
****
After trunk separation and the deorbit burn are complete, the Crew Dragon capsule weighs approximately 21,200 pounds [9,615 kg].""

And fuel mass from the In Flight Abort Test EA for the FAA.

"Dragon would contain approximately 5,650 pounds of hypergolic propellant, including approximately 3,500 pounds of dinitrogen tetroxide (NTO) and 2,150 pounds of monomethylhydrazine (MMH)."

5,650 lb is 2,560 kg.

Simple subtraction with the undocking number is 21,950 lb, which is 9,960 kg.

That's the mass with the trunk, the crew, their supplies, and some cargo for return to Earth. Granted, they had burned some fuel to get to the ISS.

whitelancer64 · « **Reply #3 on:** 01/21/2022 01:49 am »

I wanted to ask again if anyone has a better number for Dragon 2 dV

Most estimates I've seen are in the 350-400 m/s range, with a high of 450 m/s

whitelancer64 · « **Reply #4 on:** 01/21/2022 04:46 am »

From the EA for the In-Flight Abort test:

Quote

2.1.2 DRAGON TEST VEHICLE

SpaceX has developed Dragon to deliver cargo and experiments to the ISS and Low Earth Orbit (Dragon-1) and to transport astronauts to the ISS (Dragon-2) (Figure 2-1). Dragon weighs approximately 17,000 pounds without cargo and is approximately 17 feet tall with a base width of 13 feet. Dragon-2 is composed of the capsule for pressurized crew and cargo, the unpressurized cargo module or “trunk,” and a nosecone. Other primary structures include a welded aluminum pressure vessel, primary heat shield support structure, and back shell thermal protection system support structure. The thermal protection structure supports secondary structures including the SuperDraco engines, propellant tanks, pressurant tanks, parachute system, and necessary avionics.

The Dragon test vehicle is intended to represent the final flight configuration of Dragon-2. Systems, subsystems, and components critical to the success of in-flight abort would be in the final configuration. Non-critical systems would either be eliminated or simplified to reduce the complexity of the ground refurbishment process to conduct the abort test. Dragon would contain approximately 5,650 pounds of hypergolic propellant, including approximately 3,500 pounds of dinitrogen tetroxide (NTO) and 2,150 pounds of monomethylhydrazine (MMH). Dragon would contain approximately 2,400 pounds of residual propellant after the abort test.

"Dragon weighs approximately 17,000 pounds without cargo"

I am interpreting that to mean the dry mass of the Dragon capsule is about 7,700 kg, without cargo, and without trunk.

whitelancer64 · « **Reply #5 on:** 06/19/2022 10:25 pm »

The delta-v from LEO to NRHO is 3.95 km/s. Crew Dragon has approximately 400 m/s of dV.

It's safe to say that Crew Dragon is not capable of transit beyond LEO, let alone to NRHO and back to Earth.