The issue has been discussed in great detail on the usenet and elsewhere, the these discussions are archived. You are free to educate yourself, it would be unproductive to repeat the various pro and con arguments here.

Granted, it obviously flies, but are they paying a performance penalty hefting those huge H2 tanks from a standing start?

We’re discussing a launch vehicle that already exists. However, notice that the Delta IV accommodates SRBs, and that boosters don’t always have to be solid fuel based, nor do they always have to be inline with the stack, In fact, I notice several COTS competitors right now developing boosters that are going to be hydrocarbon based. Flight optimization of launch vehicle architectures still in the design stage is an even more complicated task than mission specific flight profile optimization of boosters that already exist.

The core of an Ariane V is very nearly stage and a half to low Earth orbit capable without any upper stage or payload at all. Even with all of the disadvantages of hydrogen, it is still in widespread use, which is evidence of its veracity. I don’t see that changing at all in the future, in fact, I think it will become the future fuel of choice from reusable engine considerations alone, as well as for national security and technological competitiveness. Other nations in the world seem to agree with this simple assessment.

Of course, I could be wrong, but clearly the evidence is on my side so far. It will be interesting to see how this all plays out over the decades, but now with environmental and financial bankruptcy problems pending, we no longer have the luxury of decades to work out all the little details here.

There are only a certain number and type of engines and architectures that can be pressed into immediate service to solve these problems which, admittedly, never should have existed, and only came into being in the last seven years or so. That puts a severe limit on the overall solution space.

The fact that we have a working TSTO hydrogen powered vehicle with a decent payload capability to low earth orbit (the Delta IV Medium) puts us well ahead of the curve should be decide to go the distance and develop hydrogen powered SSTO core stages, that may or may not be booster enhanced, whether solid, liquid, reusable or not, some time in the future.

I reiterate, we are not flying the underutilized boosters we have right now.

I’m looking at the problems we will be facing in ten years, in addition to the severe problems, of our own making for the most part, we are facing now.

I guess this is why it always bothered me that the Delta IV was all H2/O2 (minus the tiny solid strap-ons, of course). Granted, it obviously flies, but are they paying a performance penalty hefting those huge H2 tanks from a standing start?

I would be delighted with any and all’s insight here. Always preferred the pure orb mech to that darn rocket equation…

Thanks.

The Ariane V does it all the time, Rand, you can easily trade altitude for velocity for a subsequent burn, once you are out of the atmosphere, both drag and gravity losses are irrelevant. A booster headed for LEO is never really out of the atmosphere for the entire duration of the burn. It’s very clear to me, but I can’t understand how that can’t possibly be clear to you.

For instance, one doesn’t do circularization burns at periapsis, particularly if periapsis happens to be still in the atmosphere or even at ground level.

Have you ever flown Orbiter in your life? Do you understand the analytic complexities of launch profile optimization for even something as simple as low earth orbit transport? Try it, you might like it, it’s highly non trivial, but LEO spaceflight greatly simplifies something that is already very complex.

There are many other factors to launch system performance to consider

Of course there are, but for an existing launcher like the Delta IV Medium, the only factor to consider here is the thrust of the upper stage engine, everything else is already maxed out. Adding another RL-10 or replacing the RL-10 with an RL-60 adequately solves any Delta IV Medium problem you might encounter on the way to low Earth orbit, and you get the entire upper stage as a bonus on every flight. I don’t see anybody in the space transport industry addressing that fundamental truth. There are no conceivable performance issue for cryogenic space flight on existing launchers or using existing engines beside mass and acceleration which happens to be ‘force’ by the way, if you haven’t noticed.

As long as mass and acceleration limits, and thus dynamic pressures, structural integrity, thermal heating and the desired orbital parameters, are not exceeded, for any conceivable hydrogen launcher, you’re going to orbit.

Hydrogen is very specific that way. You do yourself and your comrades a disservice by lying about EELV black zones and the under powered nature of the Delta IV Medium in low Earth orbit applications, those are issues that has long ago been solved by straightforward means.

Even the RL-10 will get you to orbit just fine in the existing launch vehicle. The problems only arise with grossly overweight vehicles like OSP and CEV.

It’s not a “misnomer.” It’s just one more indication that you have no idea what you’re talking about.

Since cryogenic hydrogen space flight offers the highest possible performance efficiency, these are the maximum forces achievable.

The only way in which hydrogen is “high performance efficiency” (whatever that means) is specific impulse. There are many other factors to launch system performance to consider (such as bulk density, for which hydrogen is about the worst possible propellant), and the last part of your statement is meaningless gibberish. The Delta continues to have serious upper-stage performance issues for a crewed mission.

That’s about it. For GTO missions they can loft, and then use gravity as an assist, the Ariane V does the same thing, but far more effectively because of the much more powerful first stage. With the underpowered upper stage and a large payload intended for low Earth orbit missions, gravity losses will eat into your performance, far more so than the drag losses from flattening out your ascent profile to remediate the so called black zones.

Hydrogen is as powerful as a rocket fuel you will get, so whatever the performance you get from these engines is already the maximum possible.

That leaves lots of latitude for ascent profile optimization. With LEO more efficiency and acceleration is always desired, right up to the maximum allowed by the vehicle and engine. Thus is our interest in SSME SSTO.

The RL-60/MB-60 is a very credible upper stage engine niche between the RL-10 and J2-X or SSME, depending if you need ground start or air start. With the RL-60, there is almost no need at all for the J2-X at all anymore.

This kind of spaceflight will break all existing rocketry records. For instance, one could ground start an SSME along with four RL-10s, and that alone is very nearly approaching SSTO performance, and the acceleration problem of the SSME is solved. However, a single RL-10 is not sufficient.

We’ve already gamed most of this stuff out in Orbiter, it’s very simple.

That we are not flying the Delta IV Medium now is a travesty.

Let me add another relevant article, care of Space Pragmatism blog (go there if this link doesn’t work), from Areo-news.net:

http://www.aero-news.net/index.cfm?ContentBlockID=44ee108e-5aa9-402a-9e5c-e28a853a2c60

From the article:

“Other NASA insiders tell the Sentinel this shaking syndrome — and other rumored problems, yet to be discussed publicly — leave more than a few people scratching their heads at whether NASA’s Ares program is worth continuing.

Many dissenters are lobbying presidential candidates to abandon the program outright. NASA officials admit political support for the Constellation program is shaky, especially given its projected cost of $26.3 billion between 2009 and 2013, including $7.5 billion for Ares I.”

Personally, I’d say let Constellation go do whatever it wants, as long as what I consider higher priorities – COTS, Centennial Challenges, modest X planes, robotic science missions, general use of commercial services in the spirit of the Zero-G deal – are funded adequately, which I don’t think they are now.

Failing that, of course given past failures in NASA rocket and human spaceflight development programs, I’m especially focused on technical, management, and political problems with Constellation. Apparently a lot of other people feel the same way. This should have been expected from the start from the NASA Constellation folks. Rather than taking a seige mentality, they should have taken the expected scrutiny as an opportunity to make a program that from the start is reviewed openly and independently, that takes advantage of commercial possibilities to reduce risk and expense, that doesn’t add unnecessary requirements (ISS/Moon/Mars all in the same vehicle, 4 people and equipment to the lunar surface, etc), and that inherently brings in new supporters (eg: commercial, international) rather than alienates existing supporters (eg: science).

I don’t see you as accepting that responsibility. So educate us, please.