SpaceX to reveal their manned DragonV2 capsule tonight

[shynung]

"The end of decades long LEO exploration occured when, stunned by the smell and thus lacking proper judgment, a newbie astronaut caressly opened the window."

Seems like a Kerbal way to lose an entire station. Other than playing darts in an inflatable module, I think.

[sojourner]

As other say you want padding, you also want strap down points for equipment/ luggage, you also want 7 seats the model only have 4.

1. It had padding, they may add more, but that doesn't make the seats shown "mockups".

2. um, yes, you do want places to stow equipment, how does this relate to the seats being mockups?

3. As noted, there were 7 seats, just find the right images.

[sgt_flyer]

It seems someones has been able to reproduce the dragon v2 UI.

https://s3.amazonaws.com/pushbullet-uploads/udqSJ-BHDliy8kJw7iA8oo1QKBEBpmBunvtAUY/dragon%202%20ui%20screen%20rev1.png

Given that the dracos / superdracos will be used to perform orbital manoeuvers and deorbit / propulsive landings, it should even be able to make a propulsive landing after an abort. I'm really starting to wonder how much delta-v the capsule will have. (Besides, i think they will only use the fuel tanks that are inside the spacecraft - as they'll be able to reuse them, that allows them to use pricey lightweight & resilient alloys for them, which would not be considered for non reusable spacecrafts.

[Nibb31]

The abort sequence is:

- separate trunk from upper stage

- fire Super Dracos

- separate trunk from Dragon

- deploy parachutes

- splashdown

If the SDs are used for launch abort, then they won't have enough dV for a propulsive landing.

[CaptRobau]

How does the parachute sequence work. The Soyuz needs to fire small booster to slow it down enough for the crew to get out alive. Does the Dragon use its SuperDraco's for this?

It seems someones has been able to reproduce the dragon v2 UI.

https://s3.amazonaws.com/pushbullet-uploads/udqSJ-BHDliy8kJw7iA8oo1QKBEBpmBunvtAUY/dragon%202%20ui%20screen%20rev1.png

Cool, but a lots of spelling errors though

[Nibb31]

How does the parachute sequence work. The Soyuz needs to fire small booster to slow it down enough for the crew to get out alive. Does the Dragon use its SuperDraco's for this ?

An abort would be over the ocean, so it wouldn't need the SDs to cushion the landing if it's a splashdown.

For a nominal landing, the parachute deploys only in if one of the SDs doesn't fire. In that case, the other SDs will fire to cushion the landing.

The Dragonfly test campaign that is starting next month is going to test all sorts of combinations of abort scenarios with and without parachutes, with various SD failure modes, and with and without the trunk for LES simulations.

[lajoswinkler]

How does the parachute sequence work. The Soyuz needs to fire small booster to slow it down enough for the crew to get out alive. Does the Dragon use its SuperDraco's for this?h

The booster on Soyuz capsule is used to cushion the fall. You can get out alive without it, but you'll be bruised and you might get a brain concussion.

[Scotius]

Not to mention get all your teeth broken - which happened in one of early Soyuz test flight.

[magnemoe]

The abort sequence is:

- separate trunk from upper stage

- fire Super Dracos

- separate trunk from Dragon

- deploy parachutes

- splashdown

If the SDs are used for launch abort, then they won't have enough dV for a propulsive landing.

Understand, however not sure how much dv you need for an launch abort, might also depend on attitude and situation, if second stage don't fire you don't need much trust to get away, an fail the first seconds and you will use most you fuel getting away

You still has the option to use the SD to reduce landing speed

[lajoswinkler]

Not to mention get all your teeth broken - which happened in one of early Soyuz test flight.

That's why they should wear teeth protectors and keep their mouths shut during the landing.

[sojourner]

For a nominal landing, the parachute deploys only in if one of the SDs doesn't fire. In that case, the other SDs will fire to cushion the landing.

It can do a full powered landing without chutes with up to 2 failed superdracos. As long as those 2 are not in the same pod. In which case it would have control authority issues.

[Nibb31]

It can do a full powered landing without chutes with up to 2 failed superdracos. As long as those 2 are not in the same pod. In which case it would have control authority issues.

Yes, but if one SD fails before the chute deployment minimum altitude, they will deploy the chute at any rate, just in case another failure occurs. In that case you would have a power-assisted parachute landing with as many SDs are available. You would also probably have balance problems if those 2 failing thrusters are in the same pod.

There will be a whole slew of failure modes depending on where and when in the descent profile the failure occurs, the type of failure, and the minimum parachute deployment height. The only "black zone" I can think of is if suddenly 2 SDs in the same pod (or man than 2 SDs) fail below the safe parachute deployment altitude. This is very unlikely.

SDs are hypergolic thrusters with very few moving parts (only a couple of valves). They are designed to be robust enough for launch abort scenarios. While a valve can get stuck (and has on a previous CRS mission), it usually happens when the thruster is first used. In the Dragon v2, they will fire for deorbit, and several times during descent, so there will be ample time to discover a faulty thruster before reaching the minimum parachute deployment point. The chance of 2 or more SDs failing late in the mission is very unlikely.

In the aforementioned "bad luck" scenario of a double failure on the same thruster pod, they would probably deploy the chute anyway, cut off the opposite thrusters to maintain attitude, fire the others as hard as they can, and hope for the best.

Edited June 1, 2014 by Nibb31

[Scotius]

Do we have any data how much dV Dragon 2 carries, and how high its TWR is?

[Nibb31]

Not really. I've seen figures of a few hundred m/s. We don't even know if the Dragon V2 has its own tanks to expand the dV on orbit.

[Scotius]

Couple hundred? So it can't be used as a lunar lander on its own. I still fondly remember early plans for lunar exploration from Clarke's book "Interplanetary flights".

[Streetwind]

I'm expecting that the DragonV2 is a LEO taxi and is not radiation hardened for leaving the Van Allen belt.

As for TWR, well, you'd need the weight of the fully manned and fueled capsule. Eight SuperDracos give it up to 584 kN of thrust, but it's not fully retrograde (the engines are angled outward slightly), so the actual acceleration force will be slghtly less. The capsule needs at least six SuperDracos (438 kN) to perform its landing. Experience in KSP tells me you want more TWR when landing than when launching, so it can probably take off on five or maybe even four SuperDracos... it just won't have the TWR to brake for a landing.

Let's make a blind guess and say that it needs 400 kN retrograde force to achieve a sea level TWR of 3. That gives us 13.6 tons of capsule mass. Does that make sense? The Falcon 9 v1.1 that's meant to carry it is rated for 13,150 kg to LEO. Seems a pretty good estimate then that the Dragon V2 weighs in the neighborhood of 13 tons on the pad, and thus a bit less when returning from orbit without its solar trunk (unless they abuse it as an ISS cargo returner and load on extra stuff).

Edited June 1, 2014 by Streetwind

[R0cketC0der]

I'm expecting that the DragonV2 is a LEO taxi and is not radiation hardened for leaving the Van Allen belt.

As for TWR, well, you'd need the weight of the fully manned and fueled capsule. Eight SuperDracos give it up to 584 kN of thrust, but it's not fully retrograde (the engines are angled outward slightly), so the actual acceleration force will be slghtly less. The capsule needs at least six SuperDracos (438 kN) to perform its landing. Experience in KSP tells me you want more TWR when landing than when launching, so it can probably take off on five or maybe even four SuperDracos... it just won't have the TWR to brake for a landing.

Let's make a blind guess and say that it needs 400 kN retrograde force to achieve a sea level TWR of 3. That gives us 13.6 tons of capsule mass. Does that make sense? The Falcon 9 v1.1 that's meant to carry it is rated for 13,150 kg to LEO. Seems a pretty good estimate then that the Dragon V2 weighs in the neighborhood of 13 tons on the pad, and thus a bit less when returning from orbit (unless they abuse it as an ISS cargo returner and load on extra stuff).

Don't forget that they will also be used as a launch escape system, so at full throttle they will probably produce more than 6gees of accellearation.

[Nibb31]

I don't understand your comment. Dragon never was intended as a lunar lander. There have been proposals to use it as a Mars lander, but those predate the V2 vehicle so they are based on conjecture about Dragon's performance. For Mars, most of the deceleration would be done by aerobraking and you would still need the parachute.

Besides, you could land just about anything on the Moon if you use a crasher stage.

Soyuz has a dV around 400m/s. I seem to remember reading that Dragon would have 600m/s, but judging by the size of both vehicles, that sounds optimistic without additional tanks.

Edited June 1, 2014 by Nibb31

[Streetwind]

Don't forget that they will also be used as a launch escape system, so at full throttle they will probably produce more than 6gees of accellearation.

They won't carry the trunk during abort, and I was calculating with 6 SuperDracos when there are actually 8.

But it's a good point. If you start from the assumption that you'll have a minimum TWR of 6 with, say, 550 kN of effective retrograde thrust, then the capsule alone (not counting solar trunk) can't weigh more than 9.35 tons.

[Nibb31]

The trunk has fins which are specifically to maintain stability during an abort. The Dragon v2 would separate from the F9 with the trunk attached, and dump the trunk before splashing down downrange.

[Scotius]

I don't understand your comment. Dragon never was intended as a lunar lander. There have been proposals to use it as a Mars lander, but those predate the V2 vehicle so they are based on conjecture about Dragon's performance. For Mars, most of the deceleration would be done by aerobraking and you would still need the parachute.

Besides, you could land just about anything on the Moon if you use a crasher stage.

Soyuz has a dV around 400m/s. I seem to remember reading that Dragon would have 600m/s, but judging by the size of both vehicles, that sounds optimistic without additional tanks.

I'm sorry, i was not precise. In his early book "Interplanetary Flights" Arthur Clarke proposed a lunar lander very similiar in appearance to Dragon v2. Unlike LEM that ship would be single stage to lunar orbit, capable of returning to LEO and being used multiple times (after refuelling and maintenance at space station). Unfortunately Dragon is too small, and carries too little fuel to work as Clarke intended .

[Streetwind]

It's also using the wrong engines, because single stage to lunar orbit won't work with under 675 Isp. And that's with a fuel/mass fraction of almost 1, i.e. you don't get any payload whatsoever. It's also without doing anything else after arriving in lunar orbit - if you wanted the dV to land or return to Earth (or both), and still do it in a single stage, you'd need even more Isp; probably at least 900 for a land and return. And if you wanted some room for payload, you'd probably want to make it at least 1200. And, of course, all that from an engine that has enough sea level thrust to launch this gigantic mountain of fuel out of earth's atmosphere at terminal velocity.

Frankly, short of a gas-core nuclear lightbulb, I don't think mankind has the technology to pull something like that off And even that idea is a pure on-paper, speculative design concept, so it appears we won't be walking in sir Clarke's footsteps for a while yet. Single stage concepts sadly are brutally unforgiving in our "full size" solar system.

In case anyone's wondering, by the way, the SuperDracos have been quoted at 235 sea level Isp (they're hypergolic engines). Dunno about vacuum Isp, but I would be very interested if someone could find a source on that.

Edited June 1, 2014 by Streetwind

[sgt_flyer]

It's also using the wrong engines, because single stage to lunar orbit won't work with under 675 Isp. And that's with a fuel/mass fraction of almost 1, i.e. you don't get any payload whatsoever. It's also without doing anything else after arriving in lunar orbit - if you wanted the dV to land or return to Earth (or both), and still do it in a single stage, you'd need even more Isp; probably at least 900 for a land and return. And if you wanted some room for payload, you'd probably want to make it at least 1200. And, of course, all that from an engine that has enough sea level thrust to launch this gigantic mountain of fuel out of earth's atmosphere at terminal velocity.

Frankly, short of a gas-core nuclear lightbulb, I don't think mankind has the technology to pull something like that off And even that idea is a pure on-paper, speculative design concept, so it appears we won't be walking in sir Clarke's footsteps for a while yet. Single stage concepts sadly are brutally unforgiving in our "full size" solar system.

In case anyone's wondering, by the way, the SuperDracos have been quoted at 235 sea level Isp (they're hypergolic engines). Dunno about vacuum Isp, but I would be very interested if someone could find a source on that.

i don't even know if they are going to use the superdracos outside of atmosphere - they might only use the normal dracos for manoeuvers in vacuum (as they have a vacuum nozzle - the superdracos don't have one - so i expect a significantly lower ISP in vacuum )

[Scotius]

It's also using the wrong engines, because single stage to lunar orbit won't work with under 675 Isp. And that's with a fuel/mass fraction of almost 1, i.e. you don't get any payload whatsoever. It's also without doing anything else after arriving in lunar orbit - if you wanted the dV to land or return to Earth (or both), and still do it in a single stage, you'd need even more Isp; probably at least 900 for a land and return. And if you wanted some room for payload, you'd probably want to make it at least 1200. And, of course, all that from an engine that has enough sea level thrust to launch this gigantic mountain of fuel out of earth's atmosphere at terminal velocity.

Frankly, short of a gas-core nuclear lightbulb, I don't think mankind has the technology to pull something like that off And even that idea is a pure on-paper, speculative design concept, so it appears we won't be walking in sir Clarke's footsteps for a while yet. Single stage concepts sadly are brutally unforgiving in our "full size" solar system.

In case anyone's wondering, by the way, the SuperDracos have been quoted at 235 sea level Isp (they're hypergolic engines). Dunno about vacuum Isp, but I would be very interested if someone could find a source on that.

No, no. You misunderstood . Clarke's lander was much like Dragon - using chemical engines and liquid fuels. Just a lot bigger apparently. It was to be launched to LEO using typical multi-stage launcher, and after arriving in lunal orbit become orbit-to-surface, single stage, multiple use shuttle.

http://spaceshipdreams.com/wp-content/uploads/2014/04/BIS_Landing_2_RASmith.jpg

[Streetwind]

Ooooh, okay. Yes, that could easily be done with existing technology, and probably in a form factor similar to the DragonV2 (perhaps a bit larger). Though you'd probably use LH2/LOX instead of hypergolics, on account of being more conveniently replenishable on the Moon / from near Earth asteroids, and for their much better fuel economy. A quick look at the Apollo lunar module and a dV map suggests that you'd need between 4 and 5 km/s dV for this profile. The map quotes a minimum of 1.75 km/s for an ideal landing from low orbit and thus twice that for a return trip; the Apollo LM however had 4.7 km/s combined, likely to facilitate a healthy safety margin on both stages.

Assuming you could use small, vacuum optimized LH2/LOX engines like the RL10B-2 on the ULA upper stages, with around 462 Isp, you could pull off a 10 ton craft that carries 6.2 tons of fuel and 3.8 tons of dry mass (including payload) with nearly 4.4 km/s single stage dV. A single RL10B-2 with its 110 kN of thrust would offer more than enough TWR for the lunar environment even for the fully loaded craft.

Unsure how much actual payload you can cram into 3.8 tons of fully radiation hardened dry mass, though, especially if it requires life support. I expect the DragonV2 to carry significantly more payload than this imagined vessel. I mean, seven astronauts in full flight gear alone would probably clock in around 0.8 tons, not counting any of the seating, consoles, redundant computers, heating, CO2 scrubbing, air and oxygen, water, food, batteries, cargo, gyroscope, RCS thrusters plus fuel, wiring, hull mass, tank mass, engine mass...

Edited June 2, 2014 by Streetwind