Ariane 5 launching Orion

[Nibb31]

Nobody has advocated using Orion alone on expeditions. It's designed to ferry a crew of 4 to the Moon and back or to dock with a DSH and SEP tug for longer exploration missions.

Listen, I'm no fan of Orion, but Dragon is not built for BEO operations. It's as simple as that. For BEO exploration missions, it lacks:

- The delta-v to return from Lunar orbit or an Asteroid,

- The consumables and supplies for longer missions,

- The radiation and thermal shielding,

- The deep space communications and nav systems,

- EVA capability.

Sure, you could modify Dragon to have all this stuff, but it would need extensive modifications to just about every part of it and a new service module. Once you're done, you will have a cost and mass equivalent to Orion, and less room inside. I'm sure SpaceX could do it if NASA pays for it, but NASA is paying for a LEO taxi with different requirements, and that's what Dragon is.

Orion is designed and built with different requirements. Where I agree with you, is that I'm not sure that those requirements make much sense. NASA has always had an obsession about building flashy new hardware with lots of capability and worrying about the actual mission later. However, the differences between Orion and Dragon are like between a Toyota Land Cruiser and a Mini. One is good for off-roading, the other is good for cheap commuting.

Edited April 30, 2013 by Nibb31

[Temstar]

Seen as we're thinking about unlikely situation, here's an idea:

Why not launch Orion on top of a Proton? Proton can lift 21+ tons to LEO, was also designed to be man-rated for the purpose of launching the Zond spacecraft. It's cheaper. It's launched from Baikonur where manned launch facility already exist and NASA already has history of working with Russians in general and International Launch Services in particular. In fact ILS is a Russian/US joint venture and Protons are commercially available. A Proton launching an Orion seems just as (un)likely as an Ariane 5.

[Rune]

[...]

Listen, I'm no fan of Orion, but Dragon is not built for BEO operations. It's as simple as that. For BEO exploration missions, it lacks:

- The delta-v to return from Lunar orbit or an Asteroid,

- The consumables and supplies for longer missions,

- The radiation and thermal shielding,

- The deep space communications and nav systems,

- EVA capability.

[...]

Lets, see, point by point:

- Only the point about lunar return applies, since any trip longer than a few days poses the risk of frying the astronauts with the next flare, even if you reduce the crew so they can pack enough sandwiches. And the propulsion module is not american-made anyway (or has in fact passed any design review, to date), so talking about its capabilities as something to be proud of is... dubious at best.

- Plain wrong, Orion doesn't have room for those consumables either.

- Wrong, they both have the same radiation shielding (none except the food you bring with you), and the same thermal shielding (Mars return capable).

- You have me here, I admit. How much do you think it would take to stick a laser communications package to another ship like Dragon? How much do you think it weights?

- Are you serious? Orion has no airlock, so you have to depressurize to get out. How hard can it be to do the same thing on Dragon? On any interplanetary stack, the airlock is elsewhere anyhow.

Don't get me wrong, I know we mostly agree on everything. But I still think Dragon makes a better Orion than Orion, since what you want in what is essentially a crew taxi capsule, is that it doesn't take too much weight and room while you are not using it. And Orion may have some interesting capabilities, but Dragon has others, like that awesome integrated LES that gives it an huge T/W and throttle capability, or the roomy "trunk" to put unpressurised cargo in (like a robot arm or mission equipment). I would really like to see more numbers on it, of course, I have a feeling it will have more delta-v than the cargo version, but I don't know how much more. Also it will weight more than 4.2mT empty, but I don't know how much more (new docking system, more fuel, more engines). I imagine around 13mT (Falcon 9 1.1 payload, give or take), but I don't know exactly so I can't work out it's Delta-v.

Rune. And of course it blows Orion out of the water in the cost department, 140 million a pop including launch.

[Nibb31]

I can't believe I'm actually defending Orion, but:

- Only the point about lunar return applies, since any trip longer than a few days poses the risk of frying the astronauts with the next flare, even if you reduce the crew so they can pack enough sandwiches. And the propulsion module is not american-made anyway (or has in fact passed any design review, to date), so talking about its capabilities as something to be proud of is... dubious at best.

Whether the SM is made at Lockheed or at Alenia Aerospace has no bearing on its capabilities. The requirements for the service module are the same: to ferry crew to the Moon or EML-1/EML-2 with consumables for 21-days and to perform a TEI burn to get home.

The Orion Main Engine is unchanged and will still be made in the US, supplied by Aerojet, and integrated into the SM. This means that the Orion SM is pretty different from the ATV one and is actually quite similar to the Lockheed version.

- Plain wrong, Orion doesn't have room for those consumables either.

It's designed for 21-day missions as a standalone spacecraft, so I'm pretty sure it has the consumables for 21 days. Dragon does not because it is only designed to fly for 7 days.

- Wrong, they both have the same radiation shielding (none except the food you bring with you), and the same thermal shielding (Mars return capable).

Orion is planned to have some sort of shielding capability to provide temporary shelter for solar flares. When a solar flare warning is recieved, astronauts would evacuate the DSH and set up a shelter inside the Orion. I'm not sure of the details though, but that is part of the requirements. I seem to remember reading that the shelter would actually be constructed inside the cabin with removable high-density shielding panels.

- You have me here, I admit. How much do you think it would take to stick a laser communications package to another ship like Dragon? How much do you think it weights?

I don't know. It would require some sort of foldable high-gain antenna, plus some extra equipment. Extra mass anyway.

- Are you serious? Orion has no airlock, so you have to depressurize to get out. How hard can it be to do the same thing on Dragon? On any interplanetary stack, the airlock is elsewhere anyhow.

Orion has a requirement to decompress for EVA, like Apollo. This means that all the internal equipment and electronics must be hardened for use in vacuum. In addition to the depress/repress equipment, it also means that the pressure vessel must be capable of multiple depress/repress cycles and the hatch must be large enough for EVA suits. And there must be stowage room for EVA suits for all crewmembers.

The latest design of the DSH doesn't have an airlock, so EVA capability would be provided by the Orion or by the SEV.

And Orion may have some interesting capabilities, but Dragon has others, like that awesome integrated LES that gives it an huge T/W and throttle capability, or the roomy "trunk" to put unpressurised cargo in (like a robot arm or mission equipment). I would really like to see more numbers on it, of course, I have a feeling it will have more delta-v than the cargo version, but I don't know how much more. Also it will weight more than 4.2mT empty, but I don't know how much more (new docking system, more fuel, more engines). I imagine around 13mT (Falcon 9 1.1 payload, give or take), but I don't know exactly so I can't work out it's Delta-v.

We don't really know the specifications of DragonRider yet, so this is really all just conjecture. We don't even know if the LEO DragonRider will have a trunk, but a DragonRider modified for the same missions as Orion would need a service module instead of a trunk. To fill the same NASA requirements, it would need the same amount of delta-V, and therefore a similar amount of propellant. The Orion SM is 3.5t empty, and carries 8t of propellant. Add that to a 8-10t loaded Dragon and you are in a similar weight range as Orion.

Edited April 30, 2013 by Nibb31

[BeefTenderloin]

.... their stockpile of Block II CSMs and Saturns.

I have an image of a garage stuffed full of assembled Saturn Vs and a NASA engineer stressing over what they're going to do with them.

[Rune]

Well, Nibb31, I also can't believe I'm sounding like a SpaceX fanboy . But seriously, I think we are both right in our own way. Which is weird, because I think we also have a very similar point of view. You make perfectly valid points, and I also make perfectly valid points (IMO, of course). Orion is better for a Constellation-like lunar mission than Dragon (it's what it was designed to do, after all), Dragon makes a better crew taxi (same thing). We both agree a taxi is probably what's needed. So we'll have to agree to... well, agree

I have a feeling if we kept at it we would just repeat ourselves. But nice point about depressing requirements, I hadn't thought that through properly. Just one tiny thing: Orion and its radiation protection. As far as I understand it, it's just a measure of how much the existing design protected the astronauts, and how much it would need to be beefed up to provide survivable protection. A proper radiation shelter capable of enduring serious flares it is not.

Rune. Nitpicking is fun, wouldn't you say?