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[greenleaf1]

Seems like I read that the plane would only carry 4 people.  Is this enough man-power to do the job, so to speak?  I'm thinking of missions like repairing the Hubble and what-not - can 4 people do that job?  

[LunarOrbit]

I don't think Hubble repair missions could be done using the OSP, and not just because of the crew size. The Canadarm is necessary to grab onto Hubble, and I'm assuming that more cargo space would be necessary for the replacement parts.

[greenleaf1]

Oh, good point!  I hadn't even thought about that bit....

[Retrospector]

No, the space plane cannot service the HST, only the shuttle can do that. But I don't think seven astronaut are needed to do the job, a smaller crew can be trained for the maintenance and upgrading missions. Anyway, if nothing new is going to fly till 2008, there isn't that much planned service life planned for the HST beyond that (although I do hope it stays up and running well into the next decade). Even if full emphasis is put on another transport vehicle there will be shuttle flights for HST service for most, if not all, of the remainder of the decade. And I am guessing that at least one shuttle will remain in commission after that.

[Skyjim]

Yeah, this isn't a replacement for the shuttle - it is a different approach - crew transport with some light cargo capability. But in some respects it will have more capability than the orbiters.  Besides the (finally!) requirements for what would seem to be crew escape systems (it doesn't say "Crew escape", but it does specify lower probability of crew loss than Soyuz), the top-level requirements also include "greater on-orbit manueverability" i.e., more delta-vee than the shuttle has available on-orbit, and the ability to carry "at least four" crew - nothing says you can't design for the ability to carry more if needed.  My guess is that a smart proposal will incorporate the ability to trade off some of the light cargo uplift mass and volume for more seats.  

Likely, as Retrospector says, there will be at least one more Hubble servicing mission using the orbiters - and you can bet that there will be lots of careful planning to insure that there is a second vehicle stacked and almost ready to go when that mission flies.  The shuttle orbiter can't get to ISS from the Hubble orbit.

Think of a different approach to things like on-orbit servicing, though.  We've gotten used to launching crew and cargo together, which requires a very large, complex, and, as it turned out, fragile vehicle.  The fact is, though, that even with boosters already in production, we can do the same sorts of work, and do it cheaper than the shuttle has allowed.  The orbiter payload bay has proven to be a wonderful on-orbit workbench - but why not launch the workbench and cargo on it's own with a booster which costs roughly one-fourth of the cost of a shuttle launch?  Another booster carries your crew on the new OSP, ready to dock with the cargo tug/carrier/workbench and head off to do whatever job is needed.  We can do missions like this with the existing EELV architecture, adding  that cargo tug/carrier/workbench as an alternate payload for NASA EELVs. There's more than one way to skin a cat - and the sooner NASA has another system available to take humans  into orbit, the better.

[Skyjim]

More ramblings - Build a couple of these tug-cum-workbench vehicles, with propulsion modules which can be refuelled on-orbit, and capable of accepting things like airlock modules and extended duration supplies to support a docked OSP.  Cargo pallets as needed for the required mission. Then "garage" one or more at a space station, where they can provide backup manuevering/attitude control capability when not engaged in service missions either through teleoperation or with a docked OSP....

Jim

[Retrospector]

I remember in earlier days there was this business about the shuttles recovering satellites from low earth orbit and bringing them back to earth. There must be strict limitations on the returning cargo weight that can be accommodated. As far as I know, the return capability of the shuttles is their only unique feature v. expendable launch vehicles for moving cargo. I don't know why the robot arm and workshop couldn't be launched some other way.

[remcook]

space shuttle requirements were also largely military right?

[Orstio]

I don't know why the robot arm and workshop couldn't be launched some other way.

Why not use something similar to ESA's Automated Transfer Vehicle.  It's pressurized, and it could keep an arm similar to the one used on the ISS.

Smaller, automated vehicles could be used to send fuel and supplies to the "service station", and the OSP could carry personnel whenever service to a satellite would be necessary.

[Oak6221]

This thought just come to me. Is it possible for the OSP to be used for commercial use? The main purpose for the system is to go to LEO and dock with the station and come back again right. That seems to be a perfect fit for fledgling manned space industry.

[smich]

I think it's safe to say that the Shuttle had military requirements expected of it from the outset. It's the multi-tasking bit that has made it so expensive...

Jim, thinking about your "ramblings"(!) this is the kind of versatility required. I mulled over the various options you hint at - you could use your "garaged workbench" for setting up manned missions to Mars, surely? The possibilities are endless, I think.

Steve M

[Mentor]

well if it looks like its useful then theres no chance it`s gonna happen , what we want to do is to dress up the concept as some huge waste of money and time with lots of kudos and profitable contracts attached , and then when we have the funding and all the hardware is built and standing on the launchpad you say "fooled you!"  [smiley=costumedsmiley.gif]and just use it for more sensible purposes anyway and sod the polititians , politics and engineering don`t mix anyway, like the R101, typical committee built codge up, what many people don`t know is that the R101 had a sister ship (the R100) that had been flying for months(years?) before the R101 and had demonstrated it`s reliability worldwide, the R100 was made by private enterprise in competition with the government built R101 as a demonstration of the advantages of centralised control in manufacture over independant private companies (so the government built airship HAD to be better...whatever the facts), but it didn`t work out that way as we all know  , while the R101 was overwheight, underpowered, unstable and extended by an extra bouyancy bay to get her off the ground, the R100 was built to specification and performed exactly as expected, they nearly lost the R101 during a demonstration when it made an unexpected dive for the ground and the pilot only just saved her, they passed it off as a demonstration of manuverability , never let a government near the spanners , just get em to send you the money and a list of what they want .

Mentor.

[Skyjim]

Mentor, I think it can go either way.  Certainly it is possible to do things right when a government agency/contractor team is correctly staffed, funded, and given a clear goal and deadline.  While your point is well taken, Apollo is a much more relevant example, I think, than the R-100/R-101 programs.  

If they hold to a tightly focused requirement set, I think it's very possible for NASA and industry to build a useful vehicle - this is a fine opportunity.  Remains to be seen if it will be grasped.

On the military influence on shuttle design, the big issues were reentry cross-range, payload mass, and payload bay dimensions.  NASA had a faction which advocated a much smaller payload bay and uplift, with much less wing area and a slightly more benign reentry thermal environment - but the DOD requirements, which NASA had to meet to secure a commitment from DOD to launch all of their payloads on STS, included a big enough bay to launch big recon birds (think Hubble size) and also to make a quick return-to launch-site flight profile to Vandenberg.  Much more aerodynamic lift was required to make the launch site an orbit or two after a polar launch, so the orbiter grew the big double-delta wings.  DOD was pretty much dragged into the shuttle program, and bailed out as soon as Challenger gave them a good excuse.  Excellent example of a program whose engineering was dictated early on by politics, both the DOD stuff and the unwillingness to adequately fund.  There was no external tank on most early concepts, and a flyback liquid booster, in a few designs based on the S-1C first stage of the Saturn V, was part of the early conceptual designs.  At least one model I saw placed the orbiter on top of a winged S-1C derivative.  Some designers were on the right track early on....

The real crime was that NASA bought into their own propaganda about launch rates and turnaround costs and stuck to the original figures even after the design became a far different creature from the original concepts.  Nobody had the intellectual honesty to say that the job couldn't be done as advertised with the design chosen.   And it probably couldn't have met cost and flight rate targets with the manned liquid boosters, either - though it might not have been the safety nightmare of the design built.  Think of the implications of having a modular heavy reusable booster operational, though!  All sorts of alternate upper stage/ payload possibilties.

Sigh...