A Lower Tech Space Transportation System

John · Senior Member

A Lower Tech Space Transportation System

NUKE ROCKY44 · Senior Member

Sounds interesting to me since I always favor reusable and of course you have my attention when you mention winged orbital. The 2nd stage near orbital recovery engineering blackhole has always been a bone of contention like a blind spot in aerospace engineering.
The 2nd stage at some point would need to sprout wings or have a shape to present before the punishing blow torch effect of re-entry.

I guess you're petitioning to delete the side saddle off the shuttle. You're half way there since shuttle is dead anyway.

If memory serve me correctly googlenaut had a critique over this 2nd stage recovery launch system.

John · Senior Member

What I had in mind for the second stage reentry is that the stage will be topped with a nose with ablative heat shielding. The stage would reenter nose first. At some point a drogue chute would open from behind the engines. This would be a porous mesh of some appropriate material. The idea isn't so much to slow the stage as to keep it from tumbling by exerting a force against the direction of motion. So it would slow with aerodynamic breaking until it was slow enough to deploy main parachutes. It also might have some solid rockets behing the nose that might fire at the final seconds before splash down to reduce impact speed. The retros might not be required. This would have to be a trade study between chutes and retros to give an soft enough splash down.

Update: Perhaps a better idea would be to use an aerobrake attached to the front end of the booster like the one in Zubrin's book The Case for Mars. After burnout this mechanical device would expand to extend an umbrella like heatshield. The parachutes would deploy to achieve a soft splashdown.

Also, the same two-stage booster could orbit a payload the weight of the orbiter and contents as an alternative. One possibility could be a space tug plus payload. Another could be nuclear rocket stage.

-- Edited by John on Sunday 14th of February 2010 04:57:11 AM

NUKE ROCKY44 · Senior Member

Wondering if you looked into the following in Jim Dewar's book.

The Bussard Aspen:

see: http://smartech.gatech.edu/bitstream/1853/8402/1/aiaa_2001-3514.pdf

The Krafft Ehricke Helios:

see:
http://books.google.com/books?id=zmpxV1ygjvsC&pg=RA1-PA78&lpg=RA1-PA78&dq=Krafft+Ehricke+Helios&source=bl&ots=S5zQcVdp2m&sig=
72eMHJSgZ0ChODynUEBybafX1xM&hl=en&ei=Np13S4z4EIassQPBmoXLCQ&sa=
X&oi=book_result&ct=result&resnum=5&ved=0CBIQ6AEwBA#v=onepage&q=
Krafft%20Ehricke%20Helios&f=false

The "nose head first" seems Ok by me. My concern is the mass coming down slamming into re-entry on such a small square area (nose) and the weight behind it. Drag chutes I guess have a top limit of effectiveness especially at earth re-entry unless you're think of staggering chute deployment to increase in size to brake.

Aerobraking for earth is a hassle with all crap floating about. I say bring it down quick and simple.

John · Senior Member

Wondering if you looked into the following in Jim Dewar's book.

If you mean his method of returning a NTR engine to earth after use: the answer is yes. I really liked that one.

The Bussard Aspen is cool too. That is a different topic.

Here I was investigating the idea of what could be don't without going beyond the state of the art. After all if we are taking ten years (critics now say more) just to recreate Apollo using a lot of off the self I was getting pessimistic about a my favored hypersonic scramjet SSTO craft. Imagine what would have happend if NASA had gone that way in 2003? I also tried to consider the valid negatives on the shuttle. So I limited myself to RP-1/LOX and removed main propulsion from the orbiter.

I gave credit to von Braun in that his famous circa 1950 designs were resuable and recovered much in the way I laid out. Interesting that we don't do that. One reason is that most of the space launchers were evolved from military ballistic missiles or at least had the design philosophy. Also, what would happen if an engineer at one of our of the rocket makers proposed this? He'd be lucky not to be fired. They'd think he was trying to cut into their business base. Well there was the DC-X but it failed.

Back to the point on stage two recovery. One thing that needs to be avoided is having having the stage go unstable and tumble. It would be damaged beyond use. The purpose of the metal (?) mesh drag chute is mainly to but a force on the rear to prevent tumbling (any slowing is a secondary plus). The main slowing mechanism is an ablative nosecone in my first concept. You might need to an ablative sheath around the area of the body behind the nosecone as well. The idea is to get this thing down safe and sound so it can be reused minimal time (and cost).

I was aware of this idea:

http://www.friends-partners.org/partners/mwade/graphics/o/otv86psf.jpg

But this would be a problem having a shield like that on top of the second stage (unless you had a bulbous payload like many are now). I was skimming through Zurbin's book reading what he said about something else and noticed the mechanically extended aerobrake on his Mars Direct craft. Bingo that might be better.

If this could be worked out it would be a big game changer. Let's say a basic rocket would cost $80million. With the extra recovery features it would be larger so maybe it now costs $100 million. But, if you could average 20 used per vehicle. You'd be down to $5 million + maybe another $ 5 million (recovery, maintainance, and new aerobrake & chutes) = $10 million per launch.

NUKE ROCKY44 · Senior Member

John check this out:

SPACE SHOW CLASSROOM: Tuesday, Feb. 16, 2009, 7-8:30 PM PST: This is Lesson 3, Orbital & Flight Dynamics. Along with our co-hosts Drs. Logan and Jurist, we welcome back Dan Adamo, retired NASA Mission Control Flight Dynamics Officer. See presentation material for Lesson 3 on The Space Show Classroom blog which will be uploaded prior to this program. http://spaceshowclassroom.wordpress.com.

Don't know if you subsribe to the space show maybe a question on your ideas to guests could help you. It's kinda short notice.

-- Edited by NUKE ROCKY44 on Monday 15th of February 2010 11:32:18 PM

John · Senior Member

Thanks for the information. That series looks interesting. They are talking a lot about the many of the issues that we've been discussing here. I've already found an interesting link on the transcrip of a the last show that address these issues more from an economic view rather than from design approaches.

http://www.colonyfund.com/Reading/papers/phys_econ_leo.html

John · Senior Member

I've continued to explore issues related to my proposal (or concept). It looks to me that I need to make one modification. There is so much more advantage to making the second stage LH2/LOX than RP-1/LOX that I think that would be a good change.

I have a simple spreadsheet model that I use for "quick & dirty" analysis. I'm showing that a 100,000 pound orbiter could be launched with 2.25 million pound two-stage booster using LH2/LOX but with RP-1/LOX the booster would be 6.37 million pounds, i.e. order of magnitude of the Saturn V. So to keep this two-stage I'd say LH2 is a must.

The other issue is whether the making the second stage reusable is worth the costs. I have estimates in the range of 15% to 50% increase in the empty weight. Perhaps first stage and orbiter reusability with an expendable second stage might be better. Still thinking about that.

NUKE ROCKY44 · Senior Member

I would think LH2/LOX is better. Light hydrocarbons (propane, methane) are OK too but any hydrocarbon presents hassles (ground crew safety, extra engineering).

You get higher Isp w/ LH2/LOX simple is better unless you go metallic which is holy grail stuff.

GoogleNaut · Guru

There is also the factor of 'impulse density' which is a better gauge of overall vehicle performance in the atmospheric phase of launch. Originally the Apollo Saturn 5 was to use all kerosene and liquid oxygen stages, but the overall Isp was too low so the vehicle needed to be much heavier to achieve the same required delta-v performance. Then to increase Isp, all stages where switched to liquid hydrogen and liquid oxygen. This resulted in a theoretically improved performance, but the reality was that the liquid hydrogen tanks were so huge for the first stage, that additional atmospheric drag losses and heavier tanks (physically much bigger) negated most of the performance gains.

The final result which actually works is a comprimise: use liquid oxygen and kerosene for the first and heaviest stage. This lofts the vehicle above most of the atmosphere. Use liquid oxygen and hydrogen for the upper stage where the required impulse densiy can be less and you get more of the benefit of higher specific impulse.

Even the space shuttle uses this concept in its parallel staging: the two solid rocket boosters have a very high impulse density (the measure of the amount of Newton-Seconds per cubic meter of propellant.) They are a very compact form of lots of impulse.

John · Senior Member

A great anaysis Googlenaut. The upside of LH2 is specific impluse and the downside is bulk.

This density issues was one of the reasons that I was fucused on RP-1. The other was to avoid any embrittlement or errosion issues due to using hydrogen. I wanted to make this a very reusable system. Given the issues with recovering a stage from orbit and the fact that the second stage is probably only 25% of the rocket's cost, making only the first stage reusable is the way to go. You need LH2/LOX second stage to keep the weight to a reasonable level.

GoogleNaut · Guru

The real problem with reuse of hydrocarbon engines is coking in the coolant channels. By processing the fuel to remove all sulfur (which causes deposition of black CuS in copper clad thrust chambers) and by using multi-zone cooling typical of Russian engines like the RD-170/171/180/190 series of engines you can eliminate almost all of these problems. One further step I looked at was actually using a partially tripopellant engine that burns mostly hydrocarbon fuel, with liquid oxygen, and then uses a relatively small flow of liquid hydrogen to cool the channels in the thrust chamber, combustion chamber and nozzle throat. Some of the warm hydrogen was then used for tank pressurization of the hydrocarbon propellant tank, and the rest was used to supply fuel for the oxygen rich gas generators used to drive the turbopumps.

Thus all contamination issues of the thrust chambers are removed which then makes them 'erosion limiting' on the throat. Further adaptations may allow an engine to use a removable combustion chamber and throat so that a new liner can be used...however, at what point is 'good' good enough? The added cost and complexity required to achieve full reusability is sometimes just not warranted. An engine which costs $20M to build and $8M per flight to refurbish and has an ultimate life rating of 20 flights (such as the RD-171M) will cost something like $180M over its life...versus a $90M engine that is rated for 100 flights, but costs $20M to refurbish each flight (similar to SSME.) Reusability is not necessarily cheaper/better...it's something which was difficult for me to learn.

John · Senior Member

Well just taking your numbers a face value you have on the one hand $20M x 20 flights equals = $400M vs. $20M + $ 8M x 20 flights = $180M. That's a 55% cost reduction. That's a big step ahead. But, can we do something to reduce that $ 8M per flight?

I'm proposing reusing the whole first stage. It seems to me that you get a little more pay off on reusing liquid stages than we get with the Shuttle SRBs. On my booster we are going to have four or five engines plus the tanks, etc. My thought is that we are talking $150M vs maybe $50 M for the LH2/LOX expendable second stage.

I think one advance in my concept is seperating the orbiter from the main propulsion system. This should greatly facilitate orbiter turn around. Also, the same system is use unmanned (no orbiter) for large up to 50 payloads or for crewed missions with orbiter.

Googlenaut, I agree that this is hard but I also think that we need to continuously push in this direction or we are stuck with space just unaffordable. But, as always thanks for your cautionary comments.

-- Edited by John on Wednesday 3rd of March 2010 01:11:46 AM

NUKE ROCKY44 · Senior Member

Achieving balance at LEO is difficult to do. Designing a successful launch system that goes through all the trouble it takes to satisfy the rules of the rocket equation and fight dynamics is tough stuff. Why not place emphasis in robust systems that allow us to pry the door open toward HSF at LEO and beyond ?

However in-situ fuel dynamic production you look at you still need in-space fuel depot.

Lots of talk these days focus on cutting HSF at the knees. If all you want to do is design costs and disposable then I'd recommend astronauts take out extra life insurance.

-- Edited by NUKE ROCKY44 on Tuesday 2nd of March 2010 10:52:54 PM

John · Senior Member

Why not place emphasis in robust systems that allow us to pry the door open toward HSF at LEO and beyond?

Isn't that what I'm proposing? This system would be a replacement of the Shuttle and would maintain a lot of the capabilities. It would have a reusable orbiter that would be able to send up the same crew as the exiting system and have an internal bay to carry payloads up to ten tons. It would be launched by a booster that would have a reusable first stage. The booster could also launch 50 tons payloads in the unmanned mode.

It isnt a one for one replacement of Shuttle capabilities. It does the same on crew, only 40% for internal payload, but twice as much unmanned. It sure beats anything in the COTS programs.

-- Edited by John on Wednesday 3rd of March 2010 01:44:11 AM

John · Senior Member

I have found an example of the type of reusable booster that I was discussing at the beginning of this threat. It is a COTS type system by a company named Kistler, i.e. the K-1. This is a reusable two-stage rocket based on RP-1/LOX that is designed conservatively for resuse. The website below gives the details. It shows the recovery techniques for both stages.

http://www.rocketplanekistler.com/k1vehicle/k1vehicle.html

I little update on this. It seems that Rocketplane Kistler lost their COTS contract with NASA and the money has been given to Orbital for their Taurus II launcher. Their website gives some information and doesn't give the empty weight of the stages. I've made a rough simulation with my spreadsheet model. There are clearly some big weight penalties. What is strange is that they appear to be greatest on the first-stage. confuse

-- Edited by John on Monday 8th of March 2010 02:59:11 AM

NUKE ROCKY44 · Senior Member

Kistler if I remember began as a airstrip tethered rocket plane towed to a launch point 50K ft. in altitude where it was to launch. I think they had money problems early last decade. COTS now is difficult you almost have to have all in-house funding commited to project before NASA commits. NASA is just bonus money.

I would have stayed with the airstrip launched tethered rocket plane look where spaceship1>virgin spaceship2 is now.

John · Senior Member

Kistler was an Australian company. The K-1 was their design. It seems that they got into financial trouble and we bought out by Rocketplane which is based in Oklahoma. Perhaps it was Rocketplane that had the tethered rocket plane.

Anyway they lost the NASA money and I guess they are proceeding with private funds only. I have found any recent information on their progress. It seems they are now going with the K-1 or at least that is all the give on the website.

What is important about them is the two stage reusable booster. We already know who to make an orbiter and if it doesn't have to have the main propulsion system on board we could avoid a lot of the shuttle problems. Of course the K-1 is too small for that but it would be interesting as a test bed. I understand that the Air Force as a reusable booster project as well.

The K-1 would be a cheap way to get some practical experience. We need to find out if we can refly these thing with out the extensive repair between flights we have with the shuttle. Can the second stage be recovered intact for example?

NUKE ROCKY44 · Senior Member

"We need to find out if we can re-fly these thing with out the extensive repair between flights we have with the shuttle. Can the second stage be recovered intact for example?"

Well...reusable means robust construction, means heavy, means bigger 1st. stage boost, means more money to adhere to the rocket equation.

John · Senior Member

@Googlenaut:
Thus all contamination issues of the thrust chambers are removed which then makes them 'erosion limiting' on the throat. Further adaptations may allow an engine to use a removable combustion chamber and throat so that a new liner can be used...however, at what point is 'good' good enough? The added cost and complexity required to achieve full reusability is sometimes just not warranted. An engine which costs $20M to build and $8M per flight to refurbish and has an ultimate life rating of 20 flights (such as the RD-171M) will cost something like $180M over its life...versus a $90M engine that is rated for 100 flights, but costs $20M to refurbish each flight (similar to SSME.) Reusability is not necessarily cheaper/better...it's something which was difficult for me to learn.

Mark Bray who has a lot of experience at KSC working on the Shuttle had some interesting comments on the shuttle main engines on The Space Show last Sunday. In a response to one of my questions he indicated that the main issue with the engines was the long down times between flights. I found it a bit surprising since I had been led to believe much like you said above. You may find it interesting.

http://www.thespaceshow.com/detail.asp?q=1333