Basic Rocket Science Q & A

[kevin-rf]

Well there was that partial Titan II stage that recovered back in the 1960's. Discussion of it and pictures are somewhere in the historical threads. Russian first stages land on land and are cut up and sold as scrap. Again there is a cool set of photos linked somewhere in the historical section.

But rockets in the ocean are a drop in the bucket. I once saw (and don't have a source) a claim that there are over a million ships at the bottom of the ocean. Though it raises my eyebrow, they definately number in the thousands...

[DMeader]

I've seen some of those photos from Kazakhstan, downrange from Baikonur... sections of rocket bodies re-purposed into shelters, storage buildings, etc.

Would be interesting to see what remains of spent S1-C stages and whatnot on the bottom of the Atlantic. I wonder how much of it would be recognizable?

[Antares]

One of the downrange security forces actually shows up at the impact points on Russian rockets to ensure the first group that gets to the hardware has first dibs and that there is not a generic melee over it.

There are beach bars in the Caribbean and Bahamas that have pieces of fairings and tanks that are used as tables and chairs.  I'm not sure if I've seen pictures or if I have a good imagination.

[mars sts-107]

what if you could have the rocket engines on the launch pad so it would not a big first stage

[Spacenick]

rockets are not blown into space by a stream of air. They push them selves upwards by accelerating mass downwards (this works in any direction by the way) they work by the newtonian principle of f=ma where a is the acceleration (it's a vector meaning it implies a direction) m is the mass and f is the force working on the rocket.

Therefor you can't put the engines anywhere else then on the rocket itself.

[mmeijeri]

I have a question related to Ares I being used by NASA to relearn rocket development skills.

Let me first explain the background for my question and then get back to the Basic Rocket Science aspect.

Ares I has been criticised for many reasons and one of those reasons is that even if it ever flies, it would duplicate an existing capability. Other alternatives would be inline or side-mount SDLVs. These could not be dismissed as simply duplicating existing capability, the problem being that they exceed existing capabilities by so much that there are no payloads for it. The SDLV would not be useful until an upper stage were developed for it.

One interim solution I can think of is to use an existing upper stage (Centaur or DHCSS) to move payloads beyond LEO. Centaur would be good enough to get an unmanned and partially fueled Orion to L1 on a very slow but energy-efficient trajectory. DHCSS would be good enough for manned missions. NSF poster Jim has repeatedly expressed grave doubts as to whether MSFC would be capable of integrating this existing upper stage with the shuttle stack. The problem doesn't seem to be that the concept itself is flawed, but more that MSFC lacks recent rocket development skills.

So I've thinking about an alternative, one that fits with my continuing fascination with hypergolics. It may be without merit, but here goes anyway:

As I understand it, historically hypergolic rockets have preceded the more difficult cryogenic ones. Given that MSFC needs to relearn rocket development skills, would it help if they started with a hypergolic upper stage? And what if they built a flying battleship version first? Say no fancy Al-Li friction stir welding etc, but plain old stainless steel with plenty of margins? The thing is, an SDLV has such an enormous LEO payload that you could easily absorb the inefficiency of hypergolics. You could still do a one-launch Orion mission to L1. You might not win any prizes in the high-tech department, but if it flies, who cares?

So after this lengthy introduction, let me get to my question:

Would such a hypergolic "training stage" be substantially easier/cheaper/quicker/less risky to develop than a non-battleship cryogenic upper stage? Would it help if they started from an existing design? Or could they perhaps scale up the Orion SM drastically to turn it into a hypergolic EDS? If the answer is 'no', could you explain why?

[mmeijeri]

Another question regarding hypergolics: the other day Danny Deger mentioned that a hypergolic stage can act as a sort of shield against an exploding first stage, because it would burn, not explode. Is this something that holds for all hypergolic propellant combinations or something that's special to MMH/NTO?

[Jim]

There isn't a mission/need for another upperstage nor the money to 'train" MSFC.

My beef with MSFC is that they should be doing any LV development. Civil service performing such tasks is not needed.

[mmeijeri]

There isn't a mission/need for another upperstage nor the money to 'train" MSFC.

My beef with MSFC is that they should be doing any LV development. Civil service performing such tasks is not needed.

Agreed, but I'm working from the assumption that politicians will want to preserve the shuttle stack anyway and trying to combine this with incrementalism to reduce risk and move IOC forward. This works very well in my own field of software development.

So

- take a shiny fully-featured Altair as currently envisaged
- now downgrade it to all-hypergolic
- now downgrade it to all metal structures (perhaps even stainless steel) and no composites
- now downgrade it to a single-stage lander
- now remove the landing gear, remove the need for a deeply throttleable engine and remove all the complexities related to landing from the flight software and see if you can now use the Orion engine
- now downgrade the crew compartment to a pressurised cargo carrier
- now downgrade the pressurised cargo carrier to an unpressurised cargo carrier
- now remove the cargo carrier entirely
- now downgrade to a pressure fed system if you hadn't done so already
- now see if you can merge it with the Orion SM

Would you agree that each step above would be a simplification?

Now focusing on the basic rocket science aspect again:

When you are designing a rocket stage, what fraction of the work is taken up by upgrading from a battleship version to an optimised version? Would using stainless steel allow for earlier initial operational capability, at the expense of lower performance and later full operational capability? How much of the vibrational analysis could you eliminate? Are hypergolics substantially easier than cryogenics? If not, how about LOX/RP-1? Is pressure-fed substantially easier than pump-fed?

A fool can ask more questions than a wise man can answer...

[Jim]

- take a shiny fully-featured Altair as currently envisaged
- now downgrade it to all-hypergolic
- now downgrade it to all metal structures (perhaps even stainless steel) and no composites
- now downgrade it to a single-stage lander
- now remove the landing gear, remove the need for a deeply throttleable engine and remove all the complexities related to landing from the flight software and see if you can now use the Orion engine
- now downgrade the crew compartment to a pressurised cargo carrier
- now downgrade the pressurised cargo carrier to an unpressurised cargo carrier
- now remove the cargo carrier entirely
- now downgrade to a pressure fed system if you hadn't done so already
- now see if you can merge it with the Orion SM

Would you agree that each step above would be a simplification?

Now focusing on the basic rocket science aspect again:

When you are designing a rocket stage, what fraction of the work is taken up by upgrading from a battleship version to an optimised version? Would using stainless steel allow for earlier initial operational capability, at the expense of lower performance and later full operational capability? How much of the vibrational analysis could you eliminate? Are hypergolics substantially easier than cryogenics? If not, how about LOX/RP-1? Is pressure-fed substantially easier than pump-fed?

That is not feasible, too many changes in between.  An upperstage has different design constraints than an lander

[mmeijeri]

That is not feasible, too many changes in between.

I don't believe you, you can turn a word processor into a spreadsheet this way. It may take a while of course. Feel free to take a year for each step. Personally I'd rather have them undertake ten one-year projects than one ten-year project. I'd expect the ten one-year projects to take twenty years and deliver working hardware every two years (=twice in a presidential election cycle). I'd expect the ten-year project to take 7 years after which it would be cancelled without ever delivering working hardware.

Efficient? No. But a lot more efficient and less risky than what we have now. And less risk and earlier returns mean higher risk adjusted net present value.

  An upperstage has different design constraints than an lander

Can you elaborate? And why couldn't you do those changes incrementally?

[Jim]

But a lot more efficient and less risky than what we have now.

It is not efficient at all. There is no use for the intermediate steps.

[mmeijeri]

It is not efficient at all. There is no use for the intermediate steps.

What do you mean no use? It's a working spacecraft every step of the way.

I know you want to get MSFC out of it and I agree, but what if that's not possible?

[Jim]

It is not efficient at all. There is no use for the intermediate steps.

What do you mean no use? It's a working spacecraft every step of the way.

It isn't a working spacecraft.   The Orion SM has no guidance system.
The SM is not like upper stage nor its a spacecraft.  It is purpose built for the Orion and not very adaptable. The avionic in the CM are not made for vacuum.

But more so there are no missions for the intermediate steps.

[Jim]

I know you want to get MSFC out of it and I agree, but what if that's not possible?

Keep them away from spacecraft.

[mmeijeri]

Keep them away from spacecraft.

OK, not just launch vehicles, but spacecraft as well. Should spacecraft be left to KSC and JPL? How about fundamental research into engine technology then? Those metallised gel propellants sound interesting, would that be a valid activity for MSFC? How about ISRU propellants?

[mmeijeri]

Jim, let me start by expressing my appreciation you're taking the time to answer my persistent questions.

For those of you who might be wondering, the topic of this discussion is to what degree incrementalism is applicable to rocket development. For software development incrementalism absolutely rocks. There are those who dispute this, but they are, shall we say, less correct than they might be.

Jim, who is an expert on all things rocket seems unimpressed by my attempts at an incremental plan. It might be that the problem is with my feeble attempts, but perhaps incrementalism just doesn't apply to rockets. In favour of incrementalism I offer the example of the Russian and European space programs and less confidently the way von Braun worked on the V-2.

It isn't a working spacecraft.   The Orion SM has no guidance system.
The SM is not like upper stage nor its a spacecraft.  It is purpose built for the Orion and not very adaptable. The avionic in the CM are not made for vacuum.

OK, then let's take the required bits from the CM. Or forget about the initial steps as Orion is probably too far along anyway. Assume we start from a working Orion SM + CM.

But more so there are no missions for the intermediate steps.

Ah, but the trick is to find a convincing mission. This is hard work. I say it can be done, especially if you have an expert doing it, instead of an interested amateur like yours truly.

So here's the new and improved plan with intermediate missions added:

- Orion on EELV - crew rotation to ISS
- Orion on battleship J-130/Aquila - backup crew rotation
- Orion + battleship SDLV + SSPDM - LEO servicing missions
- stretch limo version of Orion + battleship SDLV + SSPDM - MEO servicing missions
- (stretch limo Orion + optimised SDLV) /  (Orion + optimised SDLV + upper stage) + SSPDM - GEO servicing missions
- stretch limo SM + Altair crew compartment - GEO station pressurised resupply
- extend to Altair shuttle - L1 based missions to SEL-2, GEO, LLO and NEOs
- switch to deeply throttleable engine, add landing gear, extend flight software for landings - lunar surface missions
- switch to cryogenic engines - improved performance
- use composites - improved performance

[DMeader]

So here's the new and improved plan with intermediate missions added:

- Orion on EELV - crew rotation to ISS
- Orion on battleship J-130/Aquila - backup crew rotation
- Orion + battleship SDLV + SSPDM - LEO servicing missions
- stretch limo version of Orion + battleship SDLV + SSPDM - MEO servicing missions
- (stretch limo Orion + optimised SDLV) /  (Orion + optimised SDLV + upper stage) + SSPDM - GEO servicing missions
- stretch limo SM + Altair crew compartment - GEO station pressurised resupply
- extend to Altair shuttle - L1 based missions to SEL-2, GEO, LLO and NEOs
- switch to deeply throttleable engine, add landing gear, extend flight software for landings - lunar surface missions
- switch to cryogenic engines - improved performance
- use composites - improved performance

Seems to me that making all those incremental steps and designing for missions that do not exist would be awfully, awfully expensive. Some of those steps (for instance, "use composites") should come at the very beginning, and others ("- switch to deeply throttleable engine, add landing gear, extend flight software for landings - lunar surface missions") would be better left to a vehicle designed for that mission when the requirement arose, rather than try to cut-and-paste existing into a frankenship.

[kraisee]

DMeader,
I agree.   There is a point where incremental steps just make the systems more expensive in the long term.   The right balance needs to be struck.

Generally speaking, Martijn is on a good track and the approach simply needs refinement.

Purely from the DIRECT perspective, I'll raise question marks over the following items, either because there are no requirements at this time or because they aren't actually needed to be successful:-

* Stretch limo Orion -- not required, Orion has sufficient propellant for the job already
* GEO servicing -- Are there any satellites in GEO which were ever designed for human servicing?
* GEO station -- Humans and the Van Allen Belt do not mix well. An Earth Orbiting station is safer in LEO, plus how do any other nations get a crew to a station no longer in LEO?
* Given the need to develop new engines for Lunar Landings anyway, why duplicate that effort & cost by making non-cryo engines first and then planning to upgrade them to cryo later?   It would be cheaper to just bite the bullet at the start and make a single generic system -- and the schedule currently allows us to do that
* Composites -- is there any real *need* for them?   Planned or Proposed?   With DIRECT, we currently don't need them.

Ross.

[mmeijeri]

I agree.   There is a point where incremental steps just make the systems more expensive in the long term.   The right balance needs to be struck.

It was more of a risk management thing and not wanting to wait ages before anything new flies.

Purely from the DIRECT perspective, I'll raise question marks over the following items, either because there are no requirements at this time or because they aren't actually needed to be successful:-

Interesting, because I came up with this with the need to preserve the shuttle stack in mind.

* Stretch limo Orion -- not required, Orion has sufficient propellant for the job already

The idea was to move Orion out of LEO and out of the way of commercial competitors asap, while making use of the enormous margins provided by any SDLV including a derivative of the ET. This allows the SDLV to demonstrate an immediate or at least early technical feat that had not been accomplished before. No need to fly MPLMs or ISS modules as filler missions, although the SDLV would remain available for that as a backup if necessary.

The stretch limo Orion was also meant to evolve into the Altair propulsion system slowly, meaning KSC had something to do even if a full Altair could not be funded.

* GEO servicing -- Are there any satellites in GEO which were ever designed for human servicing?

Not likely, but I suspect it would go down really well with the public. Inspecting historic satellites in a graveyard orbit would also be interesting. Or servicing training satellites, though that might be better done in MEO. These are example of "filler" mission that help you demonstrate new capabilities (as opposed to just systems) while more powerful and more difficult hardware is under development. On their own, these are probably not very good missions, and it would make sense to rack the old brain to see if you can come up with better ones. My old favourite of an Orion as a makeshift radiation research lab is one possibility. Test runs of Orion + Altair shuttles in LEO/MEO/GEO are also possible, but only after you had the shuttle.

* GEO station -- Humans and the Van Allen Belt do not mix well. An Earth Orbiting station is safer in LEO, plus how do any other nations get a crew to a station no longer in LEO?

Both are actually features, not bugs. Meant as a step towards an L1 station, where similar conditions apply. Being beyond the van Allens gives you an excellent location for radiation shielding research. This needs to be done anyway, better start now than wait for a NEO/moon mission. Prestige, no other nation can do this. Direct LOS communications allow for better telerobotics than even the ISS, since you could bypass TDRS. PR-aspect, the 'Obama-star', a permanently visible beacon of hope and change in the sky. Also meant to provide a permanent justification for the Shuttle stack, once commercial players reach LEO/L1. Excellent staging location for an Altair. It's still EOR, just a bit higher up . Back and forth to L1 for 1.4 km/s, propulsive braking is a serious possibility, even with hypergolics, even with a battleship Altair. Phasing is much easier than in LEO. Single orbit rendez-vous, cargo/crew transfer, deorbit. Aborts are much quicker than at L1. I don't believe NASA's objections to L1R are serious. GEO staging takes away the excuses of not having a lifeboat and not being able to return quickly and provides them with a new excuse to preserve the shuttle stack indefinitely, meaning noone has to lose face. Eventually use an SDLV with an ACES upper stage to launch a properly modified Dream Chaser to GEO. Should ULA ever develop Atlas Phase 2 on its own dime, it would mean there would be a commercial market for an SDLV and it could be privatised - I don't see this happening in at least 25 years. If it does not, the shuttle stack remains firmly in government hands for a long time.

* Given the need to develop new engines for Lunar Landings anyway, why duplicate that effort & cost by making non-cryo engines first and then planning to upgrade them to cryo later?

Orion already has hypergolic engines as does the Altair ascent stage. No new engine development that wasn't already planned would be necessary and some (CECE) could be delayed. A single stage design is simpler than a two stage design. Hypergolics allow low-risk propellant depots, which enables an Altair precursor to act as a near-Earth shuttle, capable of performing NEO missions. And of course I desperately want those depots to enable commercial and international participation and I just don't believe DIRECT would be able to deliver on cryo depots - much as the team might want to. GEO staging saves the shuttle stack's bacon anyway, noone needs to worry.

And a refuelable Orion + Altair shuttle allows for an early unmanned Apollo 8 to Mars.

All the cryogenics other than the ET-derivative could be moved off the critical path - including Centaur/DHCSS integration.

* Composites -- is there any real *need* for them?   Planned or Proposed?   With DIRECT, we currently don't need them.

I saw that in a late 2008 NASA Altair presentation I found on the web. It was one of about 5-7 bullet items of critical technologies NASA needed to master or mature. I can dig up the details if you like. If it's not necessary, great. I moved it to the end of the list because it didn't seem critical once you accepted depots and gateway stations.