How Best to Access the ISS-and LEO?

My vote has to be for a shuttle type vehicle.

More efficient for returning from space...and has a much larger payload capacity.

Capsule can't even begin to touch that massive shuttle payload bay.

My only change would be some sort of atmospheric jet engines to allow landing go around capability if needed.

Frank's note: So you'd nix a glider-a la HL-20, DreamChaser?

Whatever works. I would buy whatever services were available. It would be awesome to have both options...and with COTS-D we can have options.
If you can develop a way to get cargo and crew safely to and from orbit that is within my budget, I'll buy it.

Frank's note: Would a lifting body-and-expendable booster necessarily be more costly than a capsule-and-booster configuration? Both designs would, in theory, use existing proven-NASA research, wind tunnel data, etc.

How much extra stuff would a lifting body have to carry to safely abort into the ocean?

Frank's note: All the abort profiles I've seen require a small rocket motor attached to either the spacecraft base or in a unit between it and the upper stage...

Lifting body, period.

Don't use the U.S. Navy for recovery; water landing scenario should be a last resort landing mode. Water landings are terrible expensive, and corrosion becomes a life-limiting factor. Don't forget there is 15,000 feet of taxpayer-funded concrete at Launch Complex 39 needing work.

Standard and operational adoption of "fly home to launch site," with the capability of landing any location that has commercial / military ILS / GPS landing aids.

Take the cumulative data history collected on the STS, and use it to improve and refine the "Mark II" STS, which should launch on commercially-available boosters.

Produce the Mark II in such a way that it can be built on a standard that plans for total reuse, ease of repair, and off -the-shelf commercially available technology. Ease of upgrade to systems should be built into the primary structure and systems.

Vehicle should carry 6-8 passengers, and a modest amount of cargo.

Launch configuration must have the Mark II STS mounted at the pointy-end (flyover country terminology) of the launch stack, rather than side mount as with the present space shuttle orbiter. Launch configuration must include escape / abort modes using on board propulsion systems.

Let pilots fly the Mark II primarily, and have operational capability to fly back and recover in an unmanned mode.

This is the future - not spam-in-a-can. We've been there, done that. Think of the following when doing the design and production work:

"Lead, follow, or get the hell out of the way."

Frank's note: Keith, do you like the DreamChaser LB?

One other thing:

Agree with "west-texan;" atmospheric air-breathing engines should be incorporated into the Mark II STS.

Having them increases complexity of the vehicle, no doubt; however they are overdue on this kind of vehicle, and the advantages outweigh the disadvantages, IMHO.

Small steps are best. A commercial crew vehicle is the future, but it must be simple, safe and somewhat cost effective. But COTS-D should be open to any vehicle that can qualify. However capsules are safe and simple. Let the second generation COTS D vehicle fly back. Do what can be done within the funds and opportunities available.

Frank's note: But what about the time it will take to fish the capsules out of the Pacific and have the ship take weeks getting the commercial samples inside it to port?

I second that suggestion! A lifitng body with vertical take-off, horizontal landing on a runway is the only way forward. Using a capsule for LEO service is a giant leap backwards. As to bringing along a jet engine for go around capabilities, operationally that would be great, but you need to have a big enough LEO booster to accomodate the extra weight that may or may nto be used during the mission.

They need to bring on COTS-D right away, get the best out of private sector with all options on the table, including glider (HL-20 et al) with and without power assist for go-rounds. The important theme should be "let industry solve the problem of launching crew to LEO with minimal gov't oversight during the development phase". This will allow NASA to start procuring services sooner. It will also create an industry that can supply NASA's transport needs beyond LEO. This is a superior model in my humble opinion, than having NASA manage the launch vehicle development because it puts multiple potential suppliers at work doing the development, competing with each other with the incentive of having possible future crew launch services work for NASA.

I believe a capsule is the most cost effect means of access to LEO. Winged vehicles are by their nature more complicated, less rugged and more expensive to build than are capsules.

It is not given the it would require "weeks for the capsule and its contents to come back to land" after an at sea landing and I also don't believe an at sea landing is the only alternative for capsules just because NASA doesn't seem to be able to figure out how to build a capsule capable of returning on dry land.

Use the ELV fleet to launch a manned capsule designed to return to a ground landing like Soyuz. There shouldn't be too much heavy lifting to ISS after Shuttle retires, but if so, let the payload ride solo on an ELV rocket.

Gliding down to land like Shuttle is sexier but a whole lot more complicated.

I'll always pick a piloted vehicle and runway landing. And lifting bodies do not need air breathing engines- one needs only to take a look at the sheer number of approaches and landings done by the M2-F1, M2-F2, M2-F3, HL-10 and X-24 A and B to fully understand that go-around capability simply is not needed in these highly planned, highly guided steep approaches. They may look scary to the media or the arm-chair aviator, but they are in fact very efficent and safe. We're not talkin' a weekend pilot with a Cessna here folks, having "no ability to go around" is not a factor. There is no need for the weight of air-breathing engines or their fuel.

The real snag in lifting bodies as spacecraft is abort during boost and the dynamics involved and the question as to if or not that problem can be solved and what the cost will be. Lifting reentry is what I'd pick and the HL-20 style airframe will do the job just fine.

Frank:

In response to your question regarding the Dream Chaser, my answer is an unquestionable and enthusiastic "yes."

Regarding air-breathing engines, in retrospect I have to agree with Wes Oleszewski and Paul March. We have the data for making successful unpowered approach and landings from the NASA and Air Force lifting body programs, not to mention the wealth of data from STS approach and landing operations.

If I have to give up some component to achieve routine launch and landings via winged flight, I can easily make a concession of air-breathing engines.

BTW, for reference, I am a retired ATP, 7,000+ hours, with five type ratings, CFA-I / CFA-II / CFA-MEI, and FE B727. I wish I had supersonic flight experience (don't we all), and to be brutally to honest, if I ride as "spam-in-a-can" to Boldly Go, I would do it without the slightest hesitation. I am certain you can appreciate my enthusiasm for winged spaceflight, as a result.

Nevertheless, it is time we move on to the frontier of the future, instead retreating to the safety of the past. It's been 40 years....we have to get on with it. I am convinced of a fact that when societies and civilizations retreat from exploration, they die.

Thank you, Frank, for asking my opinion. I hope in some infinitesimally small way my posts contribute to pushing the ball across the goal line.

Frank's note: Keith, the approach I'm trying to take in moderating this discussion is to get everyone's ideas out there. Yours are valid and interesting observations-keep 'em coming!

You're leaving out a third option: aerial capture by helicopter. This was even contemplated for a reusable Saturn booster. The helicopter brings you straight back to the launch site. More efficient than either water landing or runway landing.

Also, I see the efficiency of landing in water, but why does that necessarily imply ocean landing? Why does the Navy have to get involved? If you have the guidance technology why not land in a fresh water lake near the landing site?

Frank's note: Wasn't this the method used to recover the first Discoverer (Corona) film capsules? And didn't they have troubles just catching that small capsule?
BTW, landing in a fresh water lake might take the capsule's reentry trajectory over populated areas?

I was not so appreciated on the concepts of full-automatic flight control for X-33, Venture Star, but I vote for the same type of LEO access vehicle developments.

Humans - Capsule, dry landing. Ie, the original plan for Orion.

Cargo - Standardised separate "capsule" types - pressurised and un-pressurised variations.

Standardised unmanned "return capsule" for large cargo if need is determined (not convinced of such a need myself).

There are many options for a manned flight service to LEO. The ISS being only one of the destinations. Rules/standards covering docking systems are needed because the space-line and space-station operator are different companies. What the launch vehicle looks like on the ground does not need specifying by NASA.

A JS-130 could lift an Orion capsule to the ISS. A JS-130 (or JS-246) could also lift the space plane from 2001 A Space Odyssey. A space plane able to take 30+ people to space is a game changing enhancement.

Use Fly Back boosters. The shuttle would be less expensive if the external tank and SRBs were replaced with liquid fueled fly back boosters. There were plans for this a long time ago.

Buzz Aldrin appears to support the idea
http://www.starbooster.com/

Frank's note: Brian-and the group-wouldn't a fly-back booster be the most expensive launch system to develop?

Two-stage VTVL, grown out from current suborbitals. Lower stage would be just a straight up and straight down booster that puts the upper stage above the atmosphere and returns to the pad. Gas it up, mate another upper stage and go.

This is not a fair question. Who really cares if you have wings or not for COTS-D? Is it not about getting crew to and from space. If a capsule is simple and cheaper than a "spaceplane", then why do a spaceplace? You want a spaceplance to fill what requirement? When was the last time that a capsule tooks "weeks" to be unloaded? I am pretty certain that the russians recover their capsules and do what they need within 2 days of it landing on the earth. Cpmplexity, cross-range ability, etc costs money and we all saw what that did to the Space Shuttle. Do we want to repeat that mistake???? If a spaceplane is better let the commerical market be the final judge.

I have a suggestion : leave arrogant pilots out of the equation. We have no use for people with geography-based feelings of intellectual superiority, no matter how skilled they may be. Be sure that any ship built and flown has the ability to re-enter by remote or autonomous control, in case the pilots are unable to get their heads through the hatch or if they pass out due to an over-abundance of carbon dioxide in their immediate vicinity.

Can you nix my last post? I jumped to my keyboard before reading that this was just about crewed launch.

"If a COTS-D solicitation is to be made, should it be opened to a lifting body as well as a blunt-bodied capsule? Would a spacecraft capable of a Shuttle-like reentry and runway landing be a more efficient way of bringing astronauts-and commercial experiment samples-back from the ISS rather than landing in the ocean and waiting weeks for the capsule and its contents to come back to land?"

First, a "Shuttle-like reentry and landing landing" does not necessarily imply a lifting body. (The Shuttle itself is not a lifting body.)

Second, when was the last time *you* chose to crash down into the ocean instead of landing on a runway?

I use the term "crash" deliberately because "splash" down is a misnomer. It implies a gentle plop into the ocean. If you look at the g-profile, it is nothing of the sort. The Apollo 12 landing was 15 gees. That's undoubtedly one reason why NASA hasn't been keen to take SpaceX up on its offer to fly ISS astronauts in used capsules.

Third, you should look at why the US Air Force went away from using escape capsules on its aircraft. You should also look at the number of close calls Soyuz has had.

The problems with capsules were well known in the 1960's. Bell Aircraft told the government the capsule approach would be "only a stunt," and 40 years of experience confirms that. The one advantage capsules have is potentially lighter weight, and if you insist on using an "expendable launch vehicle fleet," you may not be able to afford the weight of wings, landing gear, and redundant aircraft-like safety systems. Putting a reusable upper stage on an expendable booster makes sense only as a test or an interim step to a fully reusable system.

The suggestion that another hugely expensive expendable would be a "game changing enhancement" simply shows the people pushing such concepts don't understand engineering economics. What will change the game is not bigger rockets -- NASA played and lost that game in the 1960's -- but cheaper and more reliable rockets.

"Frank's note: Brian-and the group-wouldn't a fly-back booster be the most expensive launch system to develop?"

What's your evidence for that?

General Dynamics did a study in the 1960's comparing the development of the X-15 and Atlas A, a missile with similar size and performance. They concluded that the piloted, reusable vehicle was 40% cheaper to develop. An independent study conducted by the US Air Force, using different methods, reached the same conclusion.

The late Dr. Max Hunter once said that people who argue that expendables are cheaper to develop forget to develop a rocket, you need to fly rockets.

A good example of that can be seen in the SpaceShip One flight test program, which including 66 flights of White Knight and 17 flights of SpaceShip One. If SS1 had been an expendable program, it would have required building 66 first stages and 17 upper stages -- a total of 83 in all. Because it was reusable, Scaled only needed to build two vehicles to complete the program. That enabled Scaled to complete the entire program for $25 million. How many expendable rockets with that level of performance have been developed for $25 million?

Frank's note: The logic of my comment was that within the meager COTS budget, development of any kind of fly-back booster would seem to be more costly in terms of test and development than use of an existing, only-slightly-modified Atlas or Delta expendable. As far as the comparison with White Knight, imagine the true cost of the development if that aircraft AND its engines were fully charged to the space tourist program-I'd bet it wouldn't look so inexpensive then!

First I've seen of the StarBooster, and I know basically nothing about it, but I must admit (as worthless as this comment is), it looks freakin' cool! :)

My vote is to hand things over to Space X (COTS-D) or use an Atlas rocket. The Atlas series was once man rated!

But rather than discard all the work that has happened so far, I'm still hoping that they can fix what we're working on now, with the caveat that the timeline be less ... underwhelming.

Whatever works best and quickest is my motto (if you didn't notice from my ranting here). 2013 for Ares I is completely unacceptable, I ain't getting any younger!

To me, I think that we should by now be entering into the 'market forces' stage of determining basic technology. We have a growing body of experience with both glide-return and parachute-return vehicles. We also have both the 1960s/70s-era NASA and the Soviet/Russian experiences to compare water and land recovery.

Based on this, it should be possible for a sufficiently independent committee of 'wise men' to evaluate which basic configuration offers the best performance on the basis of:

1) Safety;
2) Mission performance through all flight modes;
3) Cost;
4) Effect on potential vehicle reusability.

That said, I think that COTS-D is an opportunity that should be grasped enthusiastically. NASA should issue a RFP for manned vehicles to as many vendors as possible (including international partners and 'old space' companies like ULA - and yes, I know that would mean rewriting the agreements that makes ULA exist). The objective would be to be able to run a 'fly off' between various designs to get the very best possible design available for the COTS-D mission (crew delivery to LEO).

Hopefully, having so many competitors should ensure that every viable (and some really exotic) ideas are presented. What is then important is that NASA ensure that there are no conceptual 'sacred cows'. If something really exotic like DC-X should turn out to be the best option, then they should be required to go with it, even if it is nothing like the traditional idea of a 'space rocket'.

FWIW:
My personal idea for an ideal multi-role manned spacecraft is either a lifting body or a DynaSoar-like 'space plane' with a docking airlock aft so that it can act as a 'tow truck' for specialised mission modules. These would either be launched with the crew vehicle (in the payload fairing but not attached to the CV until the LV is expended) or launched in a seperate CaLV.

The vehicle iself would launch either in a 'vanilla' form (suitable for LEO missions, mostly for ISS or Bigelow support). However, it could also be launched with a small mission module with solar cells, extra RCS and OMS fuel and extra life support consumables. These would increase the vehicle's endurance enough to make it usable for beyond-LEO exploration missions.

Special attention should be given to the design's TPS. I refuse to believe that it is impossible to build a TPS with a high degree of tolerance to MMOD impacts and to also develop an in-flight repair kit that can act as a one-re-entry mitigation for any serious breaches.

My launch performance requirement that a CLV-only flight should lie within the 25t limit for current-generation EELVs (launch by Delta-IVH, Atlas-V-5xx or Ariane-5). Future generation EELV versions, whose payload capacity goes higher than 50t, would be developed to serve as both dual-manifest C/CaLVs and pure CaLVs for missions to the Moon and NEOs. Wide-body Centaur would be developed as the EDS of choice.

There is a reason everybody and his mommy is copying the lifting body design for planned craft. Everyone knows it is simple, proven, and good for the job. And everybody wishes they were the one making it!

We should build the best earth launcher-lander. We should build the best moon launcher-lander.

Neither one of these are Apollo capsules.

Both of them will help us figure out mars.

And both of them are being worked on TODAY by PRIVATE COMPANIES.

NASA needs to buy this stuff and work on the harder problems themselves. Like the inter-planetary ferry that the lifting body would dock with. And the mining and habitation facilities on the moon. And ample funding for x-technology.

(Speaking of ferry, if the Centrifuge Accommodations Module wasn't cancelled for the ISS, we might be less far behind than we are. Right now we have a space station that can't even do the most obvious experiment on life in space. We truly don't know how to live in space without landing on earth to exercise. By now we should have been able to say "this is how much artificial gravity we need for this length of time". What a waste of the ISS capabilities.)

> I am convinced of a fact that when societies and civilizations retreat from exploration, they die.

Causality and correlation are always questions in science. I believe civilization dies when it loses ambition. Just like people. I believe what you've noticed is that when a civilization loses ambition, they also stop exploring. So the lack of exploring isn't the killer, but it is a symptom of the disease.

@Frank Yes!
To any and all options! A broad spectrum of 'interface' vessels is required, each specialised to purpose. You don't use a Tractor to pull a caravan (I was going to say "Do a Drag Race" but apparently you DO! http://www.youtube.com/watch?v=RcYNTt0ceIo "Worlds Fastest Tractor") ...nor a U-Haul to go off-roading. (Only a matter of time!)

A. Dumb Ballistic Capsules
1/ NASA should ONLY be R&Ding reusable heat shields for aerobreaking/ aerocapture egs. Lunar return to LEO, Mars, Jupiter, Titan and points beyond!) Ditto Biconic shells for downmass.
2/ LockMart should be (re)contracted to evolve the OrionII into a KISS capsule designed primarily as a land ANYHERE automated 'escape pod'. One button press and if you are anywhere between SEL1 "Dayside Station"and SEL2 "Nightside Station" you will get home! Ideally at the designated landing pad; hopefully somewhere on solid ground and finally in the drink! And if we are all at sea, recovery should be Internationalised as there may be an International Crew on board! (I.e. the various Navies provided instructions and training in recovery.)
3/ A NEW COTS-E program: a decent Orbital Module for items needed en voyage but not needed for re-entry (Toilet, ECLSS,...) OM includes LIDS (IBDM?) + CBM and thus potentially incorporated into a mini-station; OTV hab or part of a Deep Space Vessel. Reuse - Recycle - Repurpose.
4/ New official support (and funding) for Dragon... with a tranche to the best looking COTS-D backup.
5/ Revive DC-Y program and/or include Blue Origin in the next round of COTS. DOD Finance? (Ithacus!)
6/ Maintain friendly relations with other competing designs/ powers; PPTS, ARV, Shenzhou! Don't just think about international standards.

B. Winged Lifting Bodies (Gotta give those pilots someting to do!)
Pending Skylon "a game changing enhancement" (Andrew Swallow at June 1, 2009 12:40 AM)
1/NASA should ONLY be R&Ding advanced TPS, airframes, in flight liquifaction of air, hypersonic staging, ... with the view to a singlar prototype TSTO Shuttle Mk III (Pan Am Clipper) as the next Big Thing
2/ HL20/40/ Dreamchaser needs to be kicked out of its holding pattern and adopted as a Shuttle MkII... again with a tranche to the best looking backup.

PLUS (whilst we are here)
C. Game changing technologies
Tethers, Mass Drivers and other advanced concepts. A little funding here. A little funding there. But lots of technical support!

D. Bite the Nuclear bullet
NASA should be restarting research on a Deep Space Nuclear Rocket. Designed on the Earth. Tested, built and operated from the Moon.

The funding for all this may be possible if NASA makes some 'significant changes' to its current, somewhat costly program. All IMHO of course.

A reuseable would be good, if it can still be produced and used in large enough numbers to keep costs down.

The question I have is if an "impossible" ssto was built, instead of as a shuttle replacement, to ares I specs. As a four man, no cargo, people mover. Would it save costs?

It wouldn't be an all around utility truck, but it should certainly be adequate to free Orion from doing iss and Leo repair runs.

I think the Alpha Apace Station Program will be completed when it's assured crew rescue vehicle (ACRV)/ spaceplane requirements are determined and implemented.

Till then I hope the Human Space Flight Plans Committee will define their requirements for operating in low earth orbit, high earth orbit, and outer earth space. You don't have to be a rocket scientist to acknowledge it takes a bigger spacecraft loaded with the present ISS supplies or to lift a heavy load into a higher earth orbit. In the past NASA has done both with the shuttle workhorse. It generally goes into low earth orbit and from it's bay can launch payloads that are then again launched into a higher orbit.

When NASA Ground Operation design folks get the humans in space flight (astronauts) risk analysis recommendations on how humans in space will operate its all guess work on what lifting vehicle should be used. Things NASA Ground Operation designers need to work on is not only technical, like weight, sizes and transportation, but WHEN do humans leave a tetter and how much to they plan on accomplishing when they do. Supposing the spaceplane is baselined as planned then how do astronauts plan on interfacing/mating with these earth bound supply spacecraft, and what kind of supplies(scientific experiments) will be required to return to earth.

Will nodes from ISS from NASA partners have to be returned to earth, like the MPLMs? Planning for space exploration requires knowledgeable people, Example: When the space station was first designed the plan was to spend about a month at a time building it in space, however the shuttle design was not taken into account and low and behold the shuttle fleet had to be modified to stay in orbit for longer durations than the original design; also the space station had to be downsized to fit into the shuttle cargo bay.

Looks like multi-tasking vehicles are needed for future human space flight missions and NASAwatch writers have some great ideas. Let's see what Mr. Augustine's Human Space Flight Committee Report/Guidelines will be.

Frank's note: My observation (I'm no engineer and don't claim to be one) is that payload accommodations in any form of capsule shape is deficient when compared to a payload bay across the center fuselage of any type of lifting body or winged planform...agreed?

Seems like a classic no-brainer to me. But any lifting body type vehicle should be desinged for a launch on a variety of vehicles, not simply a single launch vehicle. That way, if a vehicle is down for any length of time, we do not lose access capability.

Frank's note: compatible with both Delta IV and Atlas V? Curiously, both use the derivitive RL-10 as upper stage....

There are alternatives that stand midway between capsules on the one end and winged/lifting body reentry vehicles. For example, the Kistler K-1 idea, where the TPS-protected upper stage + cargo/personnel compartment would be recovered post reentry by parachutes and airbags. There's no reason it wouldn't have worked, just lack of $$$. Another alternative would be a TSTO derivative of the Delta Clipper idea. SSTO is hard, and right on the edge of what we could conceivably do, but there's no law says you can't stack a little one on top of a big one. Both stages would be recovered by TPS-protected reentry, followed by a powered vertical landing.

Frank's note: Cost constraints would apply even more to the tiny COTS budget-if Kistler couldn't raise the funds for what many felt was the most challenging alt-access design, why would NASA fund such a technological leap-especially when most technology development money has been bled out of the agency's budget...?

So much work has been done on lifting bodies since the early 1960s that I can't understand why they aren't seen as the automatic solution to this issue. The X-24/X-38 shape has obvious advantages and has been thoroughly studied -- even the Russians came up with a similar solution. If you want more crossrange, then add small wings and get something like Cliper or the Boeing design in the graphic for this article. If you don't think runway landings are feasible, use a parasail, but definitely -- do a lifting entry with land landing. It just makes sense.

Frank's note: BTW, the CEV became a blunt bodied capsule and not a lifting body (as initially proposed by Lockheed Martin in 2005) courtesy of Mike Griffin's biases..

Frank: Based on Shuttle orbiter development experience, the answer is largely dependent on the landing loads the returned cargo (and crew) can tolerate. Fragile protein crystals don't tolerate high-G's. Injured crewperson may have limited tolerance for loads, obviously dependent on the nature of the injury.
Capsules have shocks from parachute deployment and surface impacts. Winged vehicles have shocks from touchdown and braking. Of the two, the winged vehicles were analyzed to have the lowest loads.

From a cost standpoint, the answer is different depending on the plan for reuse of the vehicle. Our great mistake in estimating the cost of reusability for the SRM/SRB and Orbiter was to neglect the safety requirement of post-flight analysis of the retrieved hardware. Lots of post-flight engineering hours and some physical reshaping of hardware, e.g., from water impact loads on the SRM/SRB, plus salt water exposure, etc; Orbiter structural integrity (including especially the Thermal Protection System) and the main propulsion system elements. We didn't come even close in estimating how much post-flight engineering hours and the number of people involved in doing limit testing, number-crunching simulations, etc. When crew safety and vehicle integrity are involved, the disposition of anomalies takes lots of time and people and meetings.

Just some thoughts for your readers to ponder...

Frank's note: Mal, many thanks for your highly informed post. In essence, though, you really have made the case for a reentry vehicle shape other than capsules for the return of commercial samples from the ISS....

I'm under the impression that landing on land is very good.

Small capsules can do that - the Soyuz does all the time.

A lot of the risks with the Shuttle's TPS involve launch debris. That's just going to be an issue with a spaceplane RLV that utilizes drop tanks. I'm under the impression that the shuttle showed such a scheme could be great for cargo if you have a lot of payloads, but is dangerous to crews.

But you can hurl a space plane into orbit on a big dumb booster just like anything else. It doesn't need to actually be an RLV. It can just be a payload. Arguments against the Shuttle aren't exactly arguments against spaceplanes in general.

Such a vehicle ought to be able to do a launch abort too. Didn't one of those vehicles - X-38? - use a parachute? Couldn't such a vehicle drop into the ocean in an abort, saving the crew even if the vehicle itself is rendered unusable?

If its a small and focused vehicle, couldn't the shield be designed stronger than the Shuttle's to better deal with MM and OD damage?

Its said that they're very expensive to develop, but the X-38 program was making a lot of progress for only several hundred million dollars.

I think it seems worth considering.

The main problem with the Shuttle system has (aside from the SRB joint problem)with damage to the TPS on liftoff. This is a direct result of using the "Navajo stack" arrangement, which was necessitated by having a vehicle that hauled both crew and cargo, plus having that 1000 mile crossrange capability (dictated by USAF, when they were paying part of the costs)!

Advances in a TPS could reduce the sensitivity to damage on liftoff with a "Navajo stack" arrangement, but it might be more cost effective to simply dump a cargo pod into the ocean. Human crews SHOULD be flown in recoverable, lifting body vehicles that can land in an emergency at places other than KSC, Edwards or White Sands. But you don't need to haul all that cargo bay space up with you.

Whatever we do, I like the idea of putting out an RFP to anyone who is likely (or even unlikely) to come up with a decent proposal. Eventually, commercial operations to LEO and other Near Earth orbits (L2, L5, etc.) will be a MUST if space exploration is to be turned into something other than a few "gee whiz" flights.

Remember, air travel by paying passengers and relatively light cargo was going nowhere fast until an almost bankrupt Southern California entrepreneur was asked by an airline to come up with something better than Boeing 247's and Ford Tri-motors. Of course, Donald W. Douglas, Sr., did have the benefit of the newer powerplants, but he and his customer put the "modern" airliner on the scene with the DC-2 and -3. (Some of the latter are still flying somewhere on this planet! And some are as old or older than me!)

NASA and the aerospace industry (including all the entrepreneurs) need to get off the dime! Either that, or we will have to learn Chinese to go into space!

Ad LEO! Ad LUNA! Ad Ares! Ad Astra!

Frank's note: Brian-and the group-wouldn't a fly-back booster be the most expensive launch system to develop?

The short answer is YES, it would be more expensive to develop.

However, the question should be first, what are the over all operational requirements for the vehicle. This is in response to the over all mission or Goal which is still being debated and never seems to be settled. If the Goal is simply access to the ISS then a capsule type vehicle would most likely suffice. If the Goal is the development of a sustainable space transportation system to access destination beyond LEO then a capsule seems to not be sufficient. Particularly if there is going to be a high flight rate.

Development cost vs operational cost. The shuttle system design was driven by a desire to cut development cost. This resulted in higher operational cost. Therefore, the development and operational cost should be considered for the system when used at a certain flight rate. The flight rate is important since the most economical vehicle design for a low flight rate will be significantly different than the most economical vehicle with a high number of flights during the life time of the system.

The underlying assumption for my support of fly back boosters and vehicles is that it is desirable to develop a long term capability that will have a high flight rate. Much has been learned from the shuttle program. One item in particular is the realization that the vehicle spends most of its time on the ground in preparation for its next fight. The shuttle is hard to work on. Future vehicles will need to be build with maintenance in mind. The F-18 is a good example of this, since it is one of the best examples of an aerospace vehicle that is easy to disassemble and reassemble, very modular. More generally, the DOD and the airlines have a lot of experience with vehicle maintenance that could be applied to future space transportation systems.

The shuttle should have been a prototype with follow on systems that allowed the technology to mature. As is well known, this did not happen.

Given your assumption that it has to be within the rather limited COTS budget, anything other than an expendable booster and a reusable capsule design would seem to be out of the question. Development, post-flight refurbishment, etc...it adds up quick.

I personally favor a lifting body (HL-20, Dreamchaser, dust off the X-38, etc), but they have to be built just so. Even tiny changes can have major consequences for handling. Remember the HL-10's first flight? How about the abysmal qualities of the M2-F2? Yes, both were eventually modified into quite good flying machines, but the experiences of the X-38 flight tests reinforced this basic tenet of lifting bodies (Not to mention the parasite weight issues involved in any lifting design...). Google "The Cold Equations of Spaceflight" for a complete article on the best way (right now) to get to space.

My personal choice for manned would be:

1) SpaceX Dragon primary;
2) Finish development and testing of the already-in-existence X-38 V201 (cooperative agreement w/whomever) for launch on EELV;
3) Fund Dreamchaser on EELV.

For cargo:

1) Current plan (SpaceX/Orbital)
2) Kistler (Hey, I can dream...)

Whichever works all-around best for the dollar, gets the ring.

Yeah, not particularly realistic.

Sigh. Ok, Frank, I'll bite, remember the Titanic?

For every 10 $billion dollar luxury spaceplane and every ten - 1 $billion dollar luxury capsules visiting a 100 $billion dollar luxury space hotel, you'll want ten - 100 million dollar human rated reentry lifeboats and a hundred - 10 $million dollar minimal cargo return nosecones which can double as crew bailout escape modules and lifeboat capsules.

This is space you're flying through at 7500 meters/second. It's a one way trip, therefore your attitude control and reentry vectors can be and are unidirectional, out the back of the nosecone, and it's basically a trip of only several hours, something a space suited astronaut can get in and bail out when things can and do go wrong, which greatly simplifies the design of these things. You want these things incorporated in every cargo and human rated rocket going up there, and fortunately they can be - it's called the nosecone aeroshield, and every rocket payload has one.

Therefore, most of your design attributes can be doubled up, attitude control, OMS, nosecone aeroshield going up, cargo and rescue going down, and they can be stacked like onions, the rescue vehicle encapsulating the lifeboat capsule, etc.

Since these things are light and float, a sacrificial hard ground landing would certainly not be out of the question, and a passenger has the option of bailing out as well.

This would be an ideal project for COTS 3.0 and newspace.

I work for NASA on shuttle. While idealistically a lifting body or such would seem best, remember that you are carrying a great amount of mass into orbit with any such vehicle that is only used for the recovery. Taking wings, tires, APUs, hydraulic systems, etc. lower your payload weight and require a larger launch vehicle. And the maintenance and between flight turnaround work is greatly increased. Finally, the cost of developing the vehicle is much greater. Possibly at some time in the future when propulsion systems become more efficient or less costly such a vehicle will become viable. However in my opinion at the present time a much less costly, simpler, and straight forward capsule is the way to go. And the time, which should be only a few days, in returning it from splash down should be far less than all the systems that would have to be tested, maintained, and verified on the winged vehicle.

How about a miniature shuttle?

Maximize crew and crew safety, and minimize cargo. In reality, you only need enough cargo to sustain the crew until the real cargo comes to dock with it. Heavy cargo can always be launched on unmanned rockets. The size of the rocket doesn't matter. Its the cost per pound launched into low earth orbit. This makes the most sense cost-wise and safety-wise. Why endanger the crew to ride a heavy cargo rocket into space. Who is risking what in this case? Is the cargo more precious than the crew? In the past, we have always clung onto putting everything in one big roll of the dice, i.e., put the whole shebang on one rocket. Doing this however inevitably ends in human tragedy forcing us to question what we are doing is safe. We always are easily convinced that going into space is risky no matter how much cargo the crew rides into space. What we don’t seem to take into account is that the human and cargo risk factor increase substantially with the size of what is being transported into space. The bigger they are, the harder they fall.

There are three parts of a payload that goes to orbit. 1) the people, 2) the cargo, and 3) the reusable structure containing the people and the cargo. If you have two separate launches, i.e., one for people and one for cargo, you have dramatically increased the mission’s complexity but you have minimized the risk to the people being transporting into space. The main reason we launch the whole shebang in one launch is primarily cost. Its done this way because rockets have to be paid for up front and it starts with the How-Much-Is-It-Going-To-Cost game played over and over until the actual launch for one rocket and one payload with many players. This game is going to change someday due to the proven capability of autonomous rendezvous with and without manned spacecraft. We will launch crews with very little cargo to autonomously or manually rendezvous with previously launched unmanned heavy cargo spacecraft already in orbit. Both of these launches will be bid out to different launch service suppliers that can best fulfill their requirements at the least cost. This docked configuration will then travel to the ISS or to the moon using people in-the-loop onboard this assembled spacecraft. The return trip from the ISS takes the assembled spacecraft safely away, the disposable section is undocked and deorbited and the crewed spacecraft glides safely back and lands on a runway.

A miniature shuttle uses nominal runway landings. Reusable. An abort during ascent replaces runway landings with a rocket jettisoning system that detaches the crew compartment from cargo compartment. It lands with parachutes in the ocean. Landing in an ocean should only be attempted due to an abort. During an abort, all bets are off other than saving lives. Just get the crew on the surface safely. Who cares if they have to wait a day or so for pick-up. They just survived a rocket abort. They should be so lucky.

People say you address all possible aborts after you have solidified a nominal design. If you design for a nominal mission, then you are limiting yourself upfront on the real flight capabilities. Its like being given a pair of cement shoes to swim with before you have learned to swim.

"Frank's note: The logic of my comment was that within the meager COTS budget, development of any kind of fly-back booster would seem to be more costly in terms of test and development than use of an existing, only-slightly-modified Atlas or Delta expendable."

Starving COTS and feeding Ares made sense if the goal was to keep human spaceflight the exclusive "province of government" (as the Aldridge Commission put it). That is not necessarily the policy today, however, and it is not the question you asked.

"As far as the comparison with White Knight, imagine the true cost of the development if that aircraft AND its engines were fully charged to the space tourist program-I'd bet it wouldn't look so inexpensive then!"

You fail to understand the difference between sunk costs and development costs. When Boeing develops a new airliner, they don't include every dollar that was spent on engine development over the last hundred years.

A fully reusable spacecraft won't necessarily cost more to develop than Shuttle C, which NASA Watch has recently flacked for (and which, like Ares, will probably turn out to cost more than the initial estimates).

As a point of comparison, NASA's 2nd Generation RLV was (justifiably) criticized as overengineered, oversized, and overly expensive. Even so, its estimated development cost was $5-6 billion, which is less than what NASA currently plans to spend on Ares I *or* the Orion capsule.

If it's politically correct to call for NASA to spend billions of dollars on Shuttle C or DIRECT, which will increase the cost of space transportation, why is it not correct to call for NASA to spend the same amount of money (or less) in a way that might reduce the cost of space transportation?

Anybody ever think about using an equivalent amount of high density wood covering an equivalent surface area on a re-entry vehicle?

Highly dense wood does not burn, it only scorches at 3,000 degrees. What do you think the bottom of the Soyuz is made of?

Answer: whatever service is safe and commercially available. Several different craft and operators would be best.

Is it really impossible to develop a reusable hot-structure heat shield that doesn't have the fragility of the Shuttle's tiles? The X-20 Dyna Soar had that structure in the early 1960s and it's very difficult for me to believe something superior couldn't be developed almost 50 years later. I have no idea what the mass penalties might be -- maybe hot structure would even be _lighter_ for all I know -- but the operational advantages would be huge and seem worth a lot of R&D investment.

@Frank:

I haven't read all the comments and I am sure some will be hair raising more than others, but:

The choice between a capsule and a lifting body or anything else for that matter is not based upon what we *like*. The choice is made through engineering and financial trade studies based upon carefully crafted requirements, or it should be! When it is not done so you get inadequate vehicles most often cancelled since they cannot be either financially sustainable or cannot live through their requirements: See the long list of vehicles since Shuttle and possibly now Orion, a blend of lifting, winged bodies and capsules. So it is important that one not think emotionnally about those decisions and rather think about them technically.

Some requirements will have a larger weight than others. For example, initially anyway, the CEV, now Orion, was supposed to be able to re-enter NO MATTER WHAT in the right heat-shield first attitude, a la Soyuz. Such requirement was based on safety first. When the decision was made to go with an Apollo like vehicle this requirement essentially went down the tube, along with part of the safety.

In addition, some people quite rightfully pointed to the added unnecessary mass to orbit, be it LEO, the Moon or Mars. I *know* Ares does not have up-mass issues but just in case, a good reminder.

COTS does not have enough funds to develop a lifting body from scratch. An ESA study showed a few years ago it would take several million dollars to *only* develop an aero database for a new such vehicle (such database is based upon Computational Fluid Dynamics suimulation and Wind Tunnel testing). So the development of the whole integrated vehicle would be essentially prohibitive. Note thaat SpaceDev is using an HL-20 vehicle for which a lot was already done by NASA. HL-20 essentially was a crewed vehicle so it is not clear, to me anyway, that it answers the cargo mission requirements. Quite often when you change the requirements you end up RE-DESIGNING your vehicle. Note that I have no idea where SpaceDev is at today and I wish they can make it as I do like HL-20. Note further that their configuration has the TPS exposed. Even though better than a Shuttle like system there still may be bird impact on ascent (the requirement for CEV was for pretty high flying bird when the stack wouldd be flying quite fast - No I don't have the requirement with me but some reader might). Finally wings are dangerous add-ons to any re-entry vehicle. I'll leave it to the readers to investigate what it took NASA to understand shock-shock interaction due to the double dela on Shutlle or shock-bondary-layer interation in areas near the wings. Such wings actually are bad during the worst part of re-entry and do not play any role for lift (check the entry angle of attack at Mach 25). However leading edge gets heated like crazy and if you depart the *correct* attitude you will for sure not land the way you'd like.

Also for some posters: Those vehicles ARE NOT piloted by a human being! Get over it! They are computer controlled. Even Shuttle is only flown by the pilot at the very end of its descent right before landing. Any idea what it takes to actually pilot a vehicle re-entering at least at Mach 25? There is no such thing as a piloted re-entry vehicle. There could be a contingency stick though but it'd still go through a computer. All modern fly-by-wire aircraft are piloted through computers. Period.

As for the water landing vs. land landing: Unlike what some would have you believe, it does not take the entire US Navy to go recover a capsule these days. There are more important consideration than just that. For example, say you want lo land at Edwards, you may have to overfly highly populated areas such a the LA basin. What do you do in case of a failure? How do you mitigate the surrounding Sierras. Yes I know Shuttle does it - Remember the cost of Shuttle? Water landing has its own drawbacks, yet either landing MUST always be considered at least for contingency landing of the other. So here again no simple answer.

Reusability is a very tricky one as one has to define reusability. Case in point: Shuttle is NOT reusable. You pretty much have to refurbish the whole vehicle every time. So again, what is reusable? The whole thing? Some components? Water vs. land landing only is part of that equation.

Well I guess I could go on and on and on. But anyone saying any different does not know what they are talking about. Sorry.

So, Frank, the question does not have a simple technical answer. Unless you're only interested with the emotional answer.

FWIW.

Frank's reply: Lots of thought to ponder here, Common Sense! My central premise was sort of like this: if you wanted to design a crewed and cargo logistics to return down mass from the ISS or other LEO destinations, what would be the best type of reentry vehicle-a capsule or a lifting shape? How and what payload accomodations would be afforded? If trajectory steering is so precise now, wouldn't capsules also have the complicating factor of where and when to jettison the service module inside the entry corridore so it doesn't land in a school yard or something? How best to attach a manipulator, assuming that one has utility in such missions, etc.

Frank, if your saying a man-tended payload should not be attached along side ten tons of TNT I agree. I recently saw part of the Ares 1 in the VAB at KSC during family visitor's day. I didn't like the telemetry area where it is presently located, but yes, its probably better than being attached along side a rocket booster.

However, if a payload is robotically operated then a risk analysis of loss of payload might be found acceptable and cheaper to lift-off.

The solid rocket boosters (SRBs) that shuttle uses today provide appropriate lifting capabilites until they are jettisoned away and the external tank (ET) continues into space.

I'm not an engineer but an observer for many years since the Bomarc's slid around the ground at CCAFS and the Redstone lighted the sky sometimes on the ground. What I do know is that NASA keeps trying to re-organize with projects instead of setting goals, ascertaining requirements, and recognizing there is more than one way to proceed. I think Mike Griffin would have eventually gotten there had it not been for having to dole out NASA funds to support polictical treaties.

Frank's note: The Shuttle arrangement whereby the orbiter is attached in essence to the first stage launch system s the worst of all possible worlds-I agree. And that configuration-what my friend Klauss Heiss called the TAOS Shuttle-was driven by budget pressures and not design excellence. Basically, the same sort of pressure these days that is serving up capsule shapes for logistic vehicles...

I'd resurrect the Delta Clipper VTOVL program. But I'd go back to some of the earlier VTOVL concepts that use several expendable exterior fuel tanks (the shuttle uses one of course) but with a twist to the concept: I'd carry the tanks into orbit where they could be:

1. grounded up in orbit and used for mass shielding a space station against cosmic radiation and micrometeorites

2. grounded up into aluminum rocket fuel for interplanetary journeys.

3. refurbished into small space stations.

4. used for reusable oxygen and hydrogen fuel tankers whenever the day comes when oxygen is manufactured and delivered from the lunar surface or from the asteroids or the moons of Mars.

or

5. used for reusable hydrogen tankers whenever hydrogen is manufactured and delivered from asteroids or the Martian moons.

I should note that some of the fuel remaining in the tanks could be scavenged and house in single oxygen or hydrogen tanks.

The VTOVL would return to Earth without the excessive weight and large surface areas of the external tanks and land vertically at the site of the original launch using small internal oxygen and kerosene rocket engines.

New empty aluminum tanks (4 to 6) would be hinged to the surface of the core VTOVL craft in preparation for refueling before the next flight.

Such a vehicle, of course, would not be limited to sites with eastern coastlines but could be launched from any site in the continental US. Such a vehicle I believe would be an attractive manned and unmanned space craft for NASA, the military, and private industry.

Frank,

More that an LES, what I was alluding to is any vehicle you launch on top of an ELV, Capsule or Lifting Body, better have the ability to land in the north atlantic, I.E. it is still going to have to float and have a parachute.

Frank's note: True, but perhaps not the entire fuselage-I think some of the lifting designs have an escape capsule in which the small seated area of the crew compartment detaches from the rest of the body and lands via parachute. The abort system I've seen for such as the DreamChaser uses a small rocket unit mounted beneath the base of the spacecraft and the adapter attaching it to the upper stage...

As long as the primary metric of cost is dollars per pound to Low Earth Orbit a capsule just robust enough to survive ascent and reentry will always win hands down. The Shuttle is a magnificent beast, but as we all know something of a hangar queen, and more important dreadfully inefficient. All that mass in structure, landing gear, and reusable engines that must be lifted all the way up into orbit just to bring it back again for landing. That's all mass you can't use for payload to orbit.
Hate to say it, but an efficient reusable fly back shuttle is beyond our current technology. I know we all grew up on Heinlein and Star Trek, but we ain't there yet. Pity, but the unvarnished truth. Rockets boosting a payload to orbit with as much of that payload being useful mass that stays there is the most efficient answer at this point in our conquest of space.

@Uncle Lar:

You get what you pay for.

Capsules always win at cost because they don't currently provide the services that the shuttles can. A Soyuz will get you to space on the cheap but that's about all it will accomplish without the aid of other rockets.

I believe if we took the basic idea of the shuttle, as a reusable manned orbiter, and stripped out the 30 thousand pound capacity cargo bay with all the accouterments this feature needed, you're back to something that could be competitive.

The only reason I think NASA is interested in disposable ships is because its good for the industry.
We built something like 20 Apollo capsules during that short program but less than ten shuttles... that's not good if your in the business of selling spaceships.

Ah. Well, I'd turn the question slightly on it's head, and go looking for the minimum crew module capable of getting up and down safely with such and so a crew size. For five to six people that's clearly an Apollo CM sized craft. It beats me why habitability resources (toilets, food, sleeping etc) have to be in the re-entry vehicle - hatches in heatshields are hardly news). In fact, as a minimum CTV (Crew Transport Vehicle) I'd say that something very similar to the Soviet TKS is just about perfect. If you *must* have a lifting body, well NASA has a perfectly acceptable design sitting in storage at JSC (last time I looked!)...

Bob Shaw

"Note thaat SpaceDev is using an HL-20 vehicle for which a lot was already done by NASA. HL-20 essentially was a crewed vehicle so it is not clear, to me anyway, that it answers the cargo mission requirements."

Actually, NASA swiped the HL-20 design from the Mig-105.

The idea that crewed vehicles cannot or should not carry cargo is "unmanned space" nonsense. Call Federal Express, or any cargo carrier in the phonebook, and ask how many unmanned vehicles they use.

"Those vehicles ARE NOT piloted by a human being! Get over it! They are computer controlled. Even Shuttle is only flown by the pilot at the very end of its descent right before landing. Any idea what it takes to actually pilot a vehicle re-entering at least at Mach 25?"

Yes, actually, I do. Gemini flew completely manual reentries, over 40 years ago. As for the Shuttle, don't believe everything you hear on teevee.

"As for the water landing vs. land landing: Unlike what some would have you believe, it does not take the entire US Navy to go recover a capsule these days."

No one ever claimed it took the entire US Navy, but even a carrier task force is an expensive proposition. If you mean to imply that it's cheap or easy, you should talk to the Navy or the Coast Guard. Search and Rescue operations at sea are *never* simple.

"For example, say you want lo land at Edwards, you may have to overfly highly populated areas such a the LA basin. What do you do in case of a failure?"

The same thing any aircraft does in case of a failure. (Aircraft have failures all the time. They're designed with enough margin and redundancy to survive most of them. You've probably flown on airliners with failed systems and not even known it.)

"So again, what is reusable? The whole thing? Some components? Water vs. land landing only is part of that equation."

No, being able to salvage some components does not make a vehicle reusable.

You make it sound like reusability is some novel, esoteric concept that no one's thought about. Aircraft have been reusable for more than a century. If you don't understand what reusability means, just go out to any airport and look around.

If we have a viable commercial crewed spacecraft we could support concepts like the old Industrial Space Facility of the 1980's (or other production facilities or hotels in LEO). One key part of this could be a tax credit (zero G, zero tax). If the total cost of putting people in space is tax free (spacecraft, launch vehicle, development and infrastructure) and any products developed (whole or in part) tax free you could then fund commercial development of a crewed lifting body spacecraft. Markets would support that. But if not, simple and safe, (a capsule funded by COTS-D) will open the doors to LEO. Like the DC-3 did for aviation.

Also, Orion will land in the Pacific Ocean between Catalina Island and LA . A Days trip back to land.

The key to developing cheaper commercial LEO launch systems is reusability and reliability. These two features are what drives the affordability of virtually all commercial electronics, appliances, and vehicles as well as passenger transportation services.

So far, two different commercial options have approached the problem of LEO access. The first approach funded primarily by COTS has been the stacked capsule design of which SpaceX is the closest to achieving a successful system. The second approach has been developing suborbital flights utilizing reusable spacecraft of which Virgin Galactic/Scaled Composites are the closest to achieving a successful system.

Should they develop a successful Falcon 9 cargo supply system, SpaceX will have achieved the lowest cost LEO launch system to date closing in on the $1000/lb benchmark. SpaceX has demonstrated their Merlin engines have the highest efficiency of any liquid-fueled rocket motors. The question still remains as to the reliability of the Falcon 9 which is still awaiting a succesful first launch. However, the Falcon 9 is not a true reusable system so there will be a production costs for each flight at this point. Such costs will make it difficult to lower the rate below $1000/lb. In order to develop a more reusable launcher, SpaceX will need to be able to tap a substantial funding to pay for high development costs which in the end may do little to lower overall launch expenditures per flight.

Should Virgin Galactic become successful, they will have developed a highly reusable and reliable system for suborbital passenger flight which will cost $200K - $250K per passenger. This approach has received virtually no government funding for its development. What is more, there is currently a passenger market for suborbital flights. The question here is whether that market will generate enough revenue to provide the capital needed to develop a true orbital launch system.

The COTS approach could produce a fairly good near short-term solution for cargo and crew LEO access with sufficient government funding. However, as long as the market remains steady, the suborbital approach may prove being the best longterm solution which requires little direct government subsidies.

One way NASA could help build a commercial market for LEO access is to develop more permanent LEO outposts besides the ISS by subsidizing the launch of Bigelow manned satellites or similar projects. They could also aid states in developing tax incentives for establishing spaceports utilizing suborbital flights.

Just IMHO

To Edward Wright:

Gus would be proud of you.

Way to go!

SpaceX has demonstrated their Merlin engines have the highest efficiency of any liquid-fueled rocket motors.

Er ... no. For that statement to be true, you would have to refine it to 1) hydrocarbon engines and 2) American engines.

Almost any advanced cycle hydrogen engine will exceed the efficiency of the Merlin, and some Russian engines beat it handily too, and you still have to consider the T/W ratios.

Furthermore on your main point, future reusable horizontally launched human craft will be 'complementary' to vertically launched cargo. There is no best method of payload delivery.

Complementary principles also apply to the liquid fuels. Dual fuels (hydrogen in the core and hydrocarbons for the boosters) almost always have better mass efficiencies than single fuels just as multistaging increases the mass efficiencies as well.

I apologize for drifting off topic.

@Edward Wright:

I stand by my comments. But best of luck with your COTS-D proposal if it ever comes to be.

To me, the 'ultimate' LEO spacecraft is a two-stage (or possible 2.5-stage with RSRMs of some type) design. Ultimately, what you are looking is a multi-compnent design with each component being re-usable (although they may not be re-used in the same flight due to differing reconditioning requirements).

Eventually, we are going to have to bite the bullet and try to create an at least partially re-usable core. This will be difficult, as this will probably require creating a rocket stage that can be de-orbited and then recovered, likely from the ocean.

Personally, I suggest an incremental approach. Start with a core design that you ultimately intend to re-use and initially use it as an expendable stage. Then slowly debug and work in the reusability features.

Here is a DC-X-derived LEO-only idea I've had:

RSRM lower stage, fully-reusable upper stage/multi-role mission vehicle. After burn-out, the RSRM makes a parachute-retarded descent and is re-used. If the curse of Ares-I is too strong and RSRM performance is never enough, develop a liquid-fuelled core that has the same features (i.e. parachute descent and water recovery).

The mission vehicle (which would probably look more like the DC-X Delta Clipper than the shuttle) would ascend to orbit using the integral US engine(s) (RL-10 or J-2X). After mission complete, the engine nozzles would be retracted behind the aft TPS cap for descent. Landing would be parachute retarded with the US main engines handling the final descent to landing on integral landing legs after parachute release.

The alternate to the retractable nozzle would be a rotating TPS cap (or the 'Sweet and Low Cap' as I call it). The cap rotates around, covering the nozzle appatures and, in the area the gaps in the TPS now occupy, there is another underlying layer of TPS.

@Frank:

Wow! Now you also added to the mission design some hardware design questions too ;) I am not hardware litterate so I'll leave it to more competent peeople to answer if they feel like doing it.

First off I'd like to say that yes capsule, today, are probably best in terms of safety/price/efficiency/mass. They may not have the cross/down-range of a lifting body but this really comes down to the requirements again. Also note that the way current capsules are used are often referred to as lifting capsules. Indeed they are designed (or at least people try to design them so!) so that they fly at a non-zero angle of attack thereby providing ever-so-limited lift. The way you fly said capsules with current guidance technology make it for, dare I say, precision landing. Also the limited lift will provide for a trajectory that limits Gs on entry and heating, loads etc. However, in case of an entry-abort one can still "safely" re-enter (see recent Soyuz descents) if you cancel lift and pretty much enter ballistically (high Gs high heating high everything but a good capsule can handle it - mostly). So, all that to say that the capsule nominally becomes a lifting body. The more pertinent question then is "how much" lift do you actually need. Well that is when you have to go back to requirements. Mostly the lift will buy you down range and more importantly cross range, that help with "precision" landing.

It is important to note that parachutes and associated subsytems have non negligible mass, and there is a trade here between chutes and wings to be done. However chutes can be packed efficiently to help with center of mass...

The payload vs. crew problem can be seen in many different ways. If you have to design an abort system for example and the vehicle includes some payload, then how do you abort? The abort system has to pull the whole crew-cargo vehicle. It might make for a gigantic abort system. The said payload also will become an issue for the location of the center of mass, on ascent and on entry. Shuttle has the problem too. Hypersonic vehicles are very sensitive to center of mass for stability and to achieve intended angle of attack on entry where aerodynamic forces are small. Most of the trajectory on entry where you have worst heating is done in a "non-controlled" way. If any, the control surfaces would not work there, so you have to bring propellant along for the thrusters to help steer and stabilize your vehicle...

It really is difficult to answer your question as you can tell. Such design is very complicated since you fly through all possible flow regimes: From hypersonics down to supersonic, transonic and subsonic. Each one of those regimes creates its own set of requirements, and quite often contradictory requirements. The "advantage" of a capsule is that somehow it does not care! It's just "falling" off the sky. Well. Not really, then there is chute deploy... arrgghh.

Service module jettison indeed needs a good look at, not just on entry but in case of an escape too. Recontact issues are important there. But the SM may be designed to burn through entry...

Anyway I think you get the picture. And this "only" is flight dynamics related issues. Then there is actual mass, avionics, structures, etc.

I am only trying to show here that there is NO simple answer. Design is an iterative process and may take several weeks/months/years depending on requirements and whether or not said requirements change during design as it seems to be happening for Orion... However, capsules are well hmmm "known" quantities, or at least we like to believe it, hence the "faster" design process.

I know what *I* would like to see but I'll keep it to myself. ;)

Hope this helps, even a little...

Frank's note: Your details help illuminate what remains, as you wisely point out, a complex equation. True, all too true!