Crew vehicles discussion

ftlwright · 2005-04-06 17:39:29

Many of the claimed drawbacks of capsules are just plain incorrect. Capsules can be reusable, as Gemini II proved, and Super Soyuz (Zarya) tried to validate. They can also be optimized for in-space transportation. You want a lighter capsule for transferring people between LEO and the moon? Build your basic earth-to-LEO capsule, but take off the heat shield and substitute lighter components wherever possible. You'd have to launch it unmanned and transfer to it from your earth-to-LEO capsule, but you'd save mass nonetheless.

Sorry, I'm going to have to disagree with you here.

Most of the studies I've heard about (I'll see if I can get this info off of the NASA document server) indicate that capsules are particularly prone to to structural deformation; due mainly to the high g loading and thermal stress during re-entry (5-6g). A reusable capsule is, IMO, a purely academic discussion as it woudl requirean entirely new launch vehicle and makes the entire argument in favor of a CEV moot. Simply, if the mission requires a reusable launch vehicle go with a lifting body; otherwise a capsule will surfice.

RobertDyck · 2005-04-06 17:45:18

Again the "wrong orbit" argument. The truth is when a vehicle approaches Earth from an interplanetary trajectory (including from the Moon) the Earth is just a ball of gravity with atmosphere. Earth's axis of rotation is irrelevant. There is no difference between an inclination of 28.5°, 51.6°, or perfectly equitorial. Inclination only affects launch because anything on the Earth is already spinning at one rotation per day.

BWhite · 2005-04-06 18:03:42

What is Kliper? A lifting body/capsule hybrid?

Zubrin has proposed a non-pressurized taxi module to mate with CEV and land on the Moon. Then the taxi module lifts off and CEV seperates to return to Earth.

srmeaney · 2005-04-06 18:19:40

With the x-38, doesn't the Hermes offer a gear down landing on an airfield?

Commodore · 2005-04-06 18:41:20

With the x-38, doesn't the Hermes offer a gear down landing on an airfield?

Hermes seems to have predated the X-38 by a decade as ESA program.http://www.astronautix.com/craft/hermes.htm]Link

But the shape is eerily similar...

Ad Astra · 2005-04-06 18:47:43

What is Kliper? A lifting body/capsule hybrid?

Kliper is a class of vehicle known as the "lifting capsule," like the LockMart OSP design. They generate some lift but are not capable of a runway landing like a lifting / winged body. All capsules are capable of generating some lift, but the lifting capsules are optimized for it.

Regarding Hermes, it's really a winged body, not a lifting body like the X-38. It has more in common with Dyna-Soar and the shuttle. Hermes was a promising project, but like so many aerospace efforts was doomed by weight growth, cost growth, and changing mission requirements. It was proposed again for the OSP but was again dropped when NASA started looking at capsules again.

GCNRevenger · 2005-04-06 19:11:35

No Robert you misunderstand... I mean with a capsule, you could abort and return directly to Earth during Lunar transit. If the Direct Return arcitecture is selected, then you could abort straight back to Earth at any time of the whole mission. This is not practical with a lifting body. Aborting back to LEO (or the ISS *spits*) will require a much more precise orbital capture maneuver too, an orbital rendevous (usually taking hours or days), and then finally the docking/transfer/undocking, before you can finally reach safety.

Or you can just drop straight back down, no muss, no fuss no waiting... great for injured crewmen or stricken space vehicles.

And I think you are misusing the Shuttle tragedy: Shuttle was a failure not so much because it was the faster, easier option but rather it was a compromise between too many competing and mutually exlusive performance requirements. One of these requirements was that it be cheap to build.

A capsule with a high degree of design dicipline can be an excelent spacecraft even with the concious decision to trade future operating costs for lower development risk/cost/time. Getting VSE into motion right now is more important that it be super cheap later on... and frankly the ISS isn't worth much effort.

Getting to the ISS from the Moon isn't much harder then equitorial no, but getting up to the ISS from Earth is, and it would reduce the number of launch windows for a Lunar mission if you departed from there... However the big thing is, that if you were to put HL-8 on top of a regular EELV, it would probobly be too heavy to reach the ISS without solid rocket boosters.

As far as reuseing a capsule on an expendable rocket being redundant, that depends on how much the capsule, or at least the expendable parts and refurbishing, costs. I don't think that the thermal warping is a show-stopper for reuseability if it were designed carefully with modern materials.

srmeaney · 2005-04-06 19:33:58

The Hermes itself is the vehicle for crew and tourist transfer between earth and a spacestation. Certainly the tool trays could be ditched for an five passenger and three crew capacity vehicle. With an airstrip landing, That would put it just above the x-38 in usefulness.

srmeaney · 2005-04-06 19:40:50

With regards to the ORVL (Orbit Return Vertical Lander) refered to as the 'delta kliper', I thought they cancelled it due to problems with the engine design?

RobertDyck · 2005-04-06 22:16:29

With regards to the ORVL (Orbit Return Vertical Lander) refered to as the 'delta kliper', I thought they cancelled it due to problems with the engine design?

Nope. No problem with the engines. NASA made some changes including a graphite/epoxy hydrogen tank and aluminum-lithium oxygen tank. The goal was to increase its range and test tank technologies for X-33. The first test flight went smoothly until they landed. Someone forgot to remove a retaining pin preventing one of the landing legs from deploying. I think it had something to do with leg hydrolics. It landed on 3 legs, fell over, broke open its fuel tanks while engines still firing, and burned. They never rebuilt it.

srmeaney · 2005-04-06 22:28:09

What was the target market for the delta klipper? it obviously was moving towards atmospheric return but in it's early stage was little more than a ISS-Lunar colony ferry.

RobertDyck · 2005-04-06 22:29:57

No Robert you misunderstand... I mean with a capsule, you could abort and return directly to Earth during Lunar transit.

Actually I do understand. The question is what exact mission scenarios would require that ability. An Apollo style blow-out of a propellant tank would require a functioning vehicle to get them back to Earth. Remember you can't abort once you start the Trans-Lunar Trajectory; orbital dynamic prevents it, you have to swing around the Moon. That means you must function for the remainder of the 3 day trip to the Moon, and the full 3 day trip back. You have to control your angle precisely enough to enter Earth's atmosphere. If you can control you trajectory that much, it's really the same to enter orbit. The only difference is rendezvous and docking instead of atmospheric entry, descent, and landing. Which is more dangerous? Abort from lunar surface: same thing.

You might not like ISS, but it's there so use it. It really does provide a safe haven, and that safe haven changes mission contingencies which change vehicle design.

This talk about Apollo 13 makes me think a big tank of hypergolic fuel isn't a good idea. LOX/Methane would be safer than Monomethylhydrazine (MMH).

RobertDyck · 2005-04-06 22:33:32

What was the target market for the delta klipper? it obviously was moving towards atmospheric return but in it's early stage was little more than a ISS-Lunar colony ferry.

The production vehicle would have been called DC-Y. http://www.astronautix.com/lvs/dcy.htm]Click here for details.

Ad Astra · 2005-04-06 22:43:50

This talk about Apollo 13 makes me think a big tank of hypergolic fuel isn't a good idea. LOX/Methane would be safer than Monomethylhydrazine (MMH).

The explosion occurred not in the propellant tanks for the main engine, but in the oxygen used for the fuel cell. Supposedly NASA has said that the CEV will use solar arrays, not fuel cells, for electrical power.

As for Delta Clipper, the original concept was to launch small "Brilliant Pebbles" interceptors. As the project was transferred from SDIO to NASA, the focus shifted. McDonnell Douglas wanted to use DC-Y / SX-1 to launch commercial satellites in the 10 MT range. The plan never materialized, and McDD tried to use DC-X as a stepping stone to the X-33. McDD lost that contract to LockMart's riskier lifting body approach. The result was two completely wasted programs, the DC-X and X-33.

GCNRevenger · 2005-04-07 08:30:59

"Remember you can't abort once you start the Trans-Lunar Trajectory"

What? Sure you can, if you are carrying TEI fuel with you. The Apollo CSM could turn right around and light up its engine and return directly home without a loop around the Moon. The only reason the Apollo-13 mission didn't was that the LEM decent module didn't have enough fuel, and the SM module engine was assumed dead.

Aerobraking into orbit is a more delicate procedure then direct entry too I bet. Its even theoretically possible for a capsule to handle reentry dead-stick... as long as you had bottled O2 and CO2 filters, you could get the crew home unpowerd after the TEI burn save for the parachute mechanism, which could even be triggerd manually... This would be a signifigant safety feature if you were coming/going from the Moon or were just going to LEO and back.

And yes, I do think that for early missions, it is a big deal to be able to come straight back rather then having to wait to rendevous with the ride back down from orbit, especially for striken astronauts or something... The point being, extra safety is another big pro in the capsule camp.

"You might not like ISS, but it's there so use it. It really does provide a safe haven, and that safe haven changes mission contingencies which change vehicle design."

Absolutely not. This is one time when the "recycling = good" mantality is irrational. The ISS is not worth maintaining even a single hour more, before or after "completion," it is worthless. Its questionable if the ISS will even be around much longer, some parts of it are getting quite old, and some of them were not designed with durability in mind. And finally, docking with the ISS as safe haven takes one thing that astronauts in an emergency don't have... TIME. It takes time to rendevous with the ISS and sync orbits, because it is at such a highly inclined orbit.

It would actually be cheaper to hire Bigelow to build a safe haven and stick it on a Delta-IV HLV closer to equitorial and leave it there with bottled LSS supplies.

SpaceNut · 2005-04-07 09:10:30

It would actually be cheaper to hire Bigelow to build a safe haven and stick it on a Delta-IV HLV closer to equitorial and leave it there with bottled LSS supplies.

Also if enough of these (bigelow hotels)are placed in synchronized orbits (relative to the ISS) and space only a small delta V burn from each other we now have more platforms to do science from and to make work for orbital assembly as well for rockets to any where.

RobertDyck · 2005-04-07 09:38:31

Um, no. TEI fuel is not enough to stop a trans-Lunar trajectory, turn around and head back to Earth, and control descent into the atmosphere. Earth is a much bigger planet than the Moon, there's a reason Apollo used a Saturn V 3rd stage for TLI but only the Apollo Service Module for TEI.

Dead stick capsule entry? No. You have to be very careful about entry angle; too steep and you burn up, too shallow and you skip off back into space.

The ISS is not worth maintaining even a single hour more, before or after "completion," it is worthless.

NASA completely disagrees with you. They are committed to complete the ISS and make productive use of it. President George W. Bush also ordered completion of ISS. NASA had discussed using ISS as a safe haven in case of Shuttle heat shield failure. I got the term "safe haven" from NASA. If you don't think ISS is a safe haven then I already have NASA on my side, and President George W.'s order to complete ISS is the clincher.

Palomar · 2005-04-07 09:54:51

Dead stick capsule entry? No. You have to be very careful about entry angle; too steep and you burn up, too shallow and you skip off back into space.

*The width of a paper's edge as compared to a basketball.

Mighty brave astronauts. :-\

--Cindy

GCNRevenger · 2005-04-07 11:06:56

Yes it is enough, because the TEI stage only has to negate the TLI burn for the little half-dozen tonne capsule and let Earth's gravity do the rest. You don't have to push the capsule and the dozen tonnes of the fueled TEI stage and the dead weight of the spent TLI stage. The Saturn-V upper stage had to push its own dead weight as well as the LEM too. With a modern high-efficency engine powerd by relativly high energy LOX/LMe, it ought to be enough for direct abort.

NASA thinks unpowerd reentry is possible if you aim is good... in fact, I do believe its a CEV requirement batted around at one time. The aerodynamics of a space capsule are, to some point, self-correcting too unlike a lift body.

A width of paper compared to a basket ball 13,000km is diameter isn't that scarry... I bet an aerobrake maneuver is much trickier though.

"NASA completely disagrees with you. They are committed to complete the ISS and make productive use of it. President George W. Bush also ordered completion of ISS."

Then NASA is WRONG. The pitiful, tiny, useless amount of science that can be done on the station is really quite sad compared to its cost. You could have build a dozen Spallation Neutron Sources, two or three accelerators like CERN, or a small fleet of Cassini-class probes.

I am convinced, since Bush has orderd the cancelation of Shuttle following ISS completion (which I believe dooms the station), that his decision was based soley on fulfilling international committments and make the "reorganization" of NASA more gradual (not firing the Shuttle Army in 04). The scientific and explorational worth of the station therefore had nothing to do with the decision.

dicktice · 2005-04-07 14:08:51

GCNR: In trying to go along with you (shocked disbelief), I still need to know where routine--repeat, routine--crew return capsule landings would take place?

GCNRevenger · 2005-04-07 15:07:36

First off, I don't think that capsules are ever going to be what you would consider routine by spaceplane standards, but thats okay, since we aren't talking about needing more then five or so per year for a long time, especially if they are six seats instead of four. Modern materials permit us to build a signifigantly larger capsule then Apollo without a big increase in mass (amorphous metals, composits, advanced titanium alloys)... I am thinking a capsule with two rows of seats split down the center if its a wide capsule, or a three-row arrangement like the "emergency apollo" design, with the back row devided by an LSS box.

Anyway, land landing it obviously preferable. Regular circular parachutes or a large ACRV style parafoil would do, with final impact cusioning with air bags (already being tested on a 6MT dead weight dummy) and/or small solid rocket motors set flush with the conic walls. Any place with some flat ground that isn't overly dangeorus (swamp, forest) near a US military or emergency recovery station would be fine I would think.

Ad Astra · 2005-04-07 15:11:21

GCNR: In trying to go along with you (shocked disbelief), I still need to know where routine--repeat, routine--crew return capsule landings would take place?

Ask the Russians where their capsules land: in vast patches of open wilderness, on the land. There's no need for US Navy recovery flotillas as long as you have braking rockets and airbags on your capsule.

Check LockMart's press releases and you'll see that they have indeed been working on the systems to enable a landing on terra firma. The Nevada Test Site, where the Genesis capsule was supposed to land, would be an ideal landing zone.

GCNRevenger · 2005-04-07 18:09:44

That would be just fine. Anywhere within half a tank of gas of a Blackhawk or a Chinook would do. To be on the safer side, probobly both small solid rockets and airbags ought to be included, with either one making the last few meters safe enough not to hurt the passengers (in their shock-absorber chairs).

Making it big enough to seat six would give signifigant future growth options when we want to do more on the Moon then visit or for a NASA-DRM type Mars mission, where you would send up the crew and dock with the orbiting ship in only one flight. The extra room that the two additional seats would also be enough for full EVA suits or other things.

srmeaney · 2005-04-08 05:23:51

Actually GCNRevenger,

Why NASA & Co. are going to finish the ISS.

Option A: Bush has a dream. It involves using the ISS as the Orbital Construction Platform for realy big Space Ships and realy big space stations and if possible, the realy big Space Cable.

Option B: It is a matter of 'saving face'. NASA is on a failure curve and for national pride reasons, they must complete something. If they don't it sets an attitude with other American-International Partner relations. America can't hold up it's end, Economy on verge of failure, America second to China.

You better hope it's option A.

RobertDyck · 2005-04-08 06:09:53

Anywhere within half a tank of gas of a Blackhawk or a Chinook would do.

You're still thinking in terms of "cost is no object" luxury. Not a helicopter, a truck. Pick up astronauts with a minivan or Hummer. Pick up the capsule with a flat bed truck with truck crane.

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