Project XR2 Ravenstar - Mk II

[dbeachy1]

But a really great job!!!

Three more things:
1.) We seriously have to think about a power supply for the XR-Ships. XR2 and 5 could carry solar panels on the inside of the PBDs. XR1 may then run on FCs, and 2 and 5 could have a FC as a reserve. I would go for solar, because the Space Shuttle today wastes so much payload weight by the H2 and O2 it has to carry for it's Fuel Cells. It could use a rollable solar panel (like DLR's Project DORA).

XR-class vessels are powered by Naquadah reactors; solar power is not practical given the ships' power requirements and the requirement that XR vessels operate far from the sun.

As for the shuttle, solar cells and batteries would be much heavier than fuel cells. In addition, fuel cells produce water -- something that is quite valuable in space.

2.) The XR7 was again mentioned somewhere above. I think we should first fill up the gaps . That means: XR2, XR3 and XR4 and of course XR6. Then we could go for the big thing^^.

Remember that each ship model can take up to a year to design, model, texture, code, document, test, and release. Each ship is a huge effort. In a nutshell, we build XR vessels for fun in our spare time, and that means we build our favorites first.

By the way: Could there be ships like an XR1.5 (inbetween of XR1 and 2)?

There is no requirement that each XR vessel be larger than the last. For example, the XR7 may in fact be slightly smaller than the XR5. The number is a model designator, nothing more.

And what is your limit for size? There surely must be a limit after which an Earth-based ship couldn't fly anymore. XR8 maybe?

The limit is how much runway and landing pad space is available: we couldn't go much larger than the XR5 simply because it wouldn't fit on the runway at KSC or a landing pad at Brighton Beach.

3.) For woo482's Rover: The X-72 shuttles in Armageddon didn't have PBDs, but a crew elevator and a ramp in the "belly". Now, the XR5 has an elevator. Couldn't it also receive a ramp on which the rover could enter and exit the vessel?

That won't work for several reasons; first, there is no room for a ramp to the cargo bay in the XR2, and second, the model is frozen at this point except for minor tweaks. Perhaps the XR3 or XR4 could have a ramp, but that would have to be designed into the model from the start.

 

[Lunar_Lander]

Hi Doug,

great to hear from you again! Thanks for the explainations. I also agree with your comment a few pages before, where you said, that a plain text cannot transmit emotions. I once was in e-mail contact with Manhigh II pilot Dr. David Simons, but to the end his answers sounded more and more annoyed. That's why I stopped writing him.

Now I just wanted to say that my post of yesterday was really meant to appreciate your and Coolhand's work . Not to offend any of you two (and of course of the rest of the forum ).

XR-class vessels are powered by Naquadah reactors; solar power is not practical given the ships' power requirements and the requirement that XR vessels operate far from the sun.

As for the shuttle, solar cells and batteries would be much heavier than fuel cells. In addition, fuel cells produce water -- something that is quite valuable in space.

What exactly is a Naquadah reactor ? I once asked you about an avanced EPS and you said it would be sopmething for an MkII release. I would really like to put my hands on the reactor controls (meltdown anyone ?)

As for the Shuttle: I just said that, because STS is liftig so much H2 and O2 just for it's power supply that it's maximum payload is serioulsy cut. STS was designed to operate in symbiosis with a Space Station and to be "fed" by it. But on, for example, Spacelab, it had to run on it's own. For the sake of experimental payload.

There is no requirement that each XR vessel be larger than the last. For example, the XR7 may in fact be slightly smaller than the XR5. The number is a model designator, nothing more.

Sorry, I had the thought: Higher number = bigger ship . Thanks for correcting me. (But on M6 somebody posted a line drawing of an XR7 being much bigger than XR5, that's why I had that thought).

That won't work for several reasons; first, there is no room for a ramp to the cargo bay in the XR2, and second, the model is frozen at this point except for minor tweaks. Perhaps the XR3 or XR4 could have a ramp, but that would have to be designed into the model from the start.

Ok, hmmmm...Wishlist for XR3: An hydraulic operated ramp in the lower side of the payload bay to allow the operations of rovers and alike motorised planetary explorations vehicles, using the vessel as an operation and resupply base (NASA document stlye )

Remember that each ship model can take up to a year to design, model, texture, code, document, test, and release. Each ship is a huge effort. In a nutshell, we build XR vessels for fun in our spare time, and that means we build our favorites first.

Well well *sighs*, spacecraft development is a long-term job...But you do it just great . Therefore I award you and Coolhand:

Have a nice day then :beach:,
Lunar_Lander

 

[Urwumpe]

As for the Shuttle: I just said that, because STS is liftig so much H2 and O2 just for it's power supply that it's maximum payload is serioulsy cut. STS was designed to operate in symbiosis with a Space Station and to be "fed" by it. But on, for example, Spacelab, it had to run on it's own. For the sake of experimental payload.

I don't know who is supplying your information about the space shuttle, but you have some wrong information here.

1. The maximum load of tanks of the Shuttle is 3-9 pairs of oxygen & hydrogen tanks. Each oxygen tank stores 781 lbm of O2, each hydrogen tank 92 lbm of H2. The oxygen is also used for life support - that's why the mixture ratio is shifted. together thats a maximum of 7857 lbm for a 18 day mission or 3600 kg. The rest of the cryo storage and fuel cell system weights around 3000 kg (one fuel cell for example weights only 255 lbm/120 kg).

Now the question is: Would a solar array be lighter?

The space shuttle fuel cells have a maximum power output of 10 kW continuous nominally and 12 kW in emergency each. That's 36 kW. And they really need it - some payloads actually strain the power on the Shuttle so much, that they need to manage power carefully.

That 36 kW is coincidally also close to the power output of one ISS solar array module of 33 kW, which also includes battery mass in its structure. Which weights 16183 kg. Solar arrays and the needed power storage weight a lot, but have the advantage of a very long endurance.

2. The Station-Shuttle Power Transfer Unit is a new addition and was not planned when the Shuttle was designed. It is ISS specific. The Soyuz capsule was designed to be powered by a space station after docking, but the Shuttle was designed from the start as a freeflyer having many capabilities of small space stations. Still, this system only allows lifting up with less EPS tanks and thus more payload - the potential increase in mission duration while docked is minimal and limited by the ECLSS of the space shuttle.

 

[Lunar_Lander]

Thanks for the info Urwumpe! Also a cookie for you

I found the info here: http://www.bernd-leitenberger.de/weblog67.shtml

Will man die Nutzlast steigern so gäbe es andere Verbesserungsmöglichkeiten. Ein grundsätzliches Problem des Space Shuttles war z.b. die Energiebilanz. Konzipiert war der Orbiter für einen Stromverbrauch von 8 kW - Apollo kam noch mit 1.5 kW aus. Doch schon vor dem Erstflug war klar, dass er 14 kW brauchen würde und Nutzlasten konnten dies noch erhöhen, z.B. wenn ein Spacelab mitflog. Das Space Shuttle nutzt Brennstoffzellen für die Stromversorgung, das bedeutet dass man für mehr Leistung mehr Wasserstoff und Sauerstoff mitführen muss. Dies geschieht in Paketen mit Tanks für Sauerstoff und Wasserstoff. ein Packet wiegt 940 kg und liefert etwa 884 kW Strom und 560 l Wasser. Bei einer 30 Tages Mission mit dem Spacelab braucht man so 15.6 t an Packs für die Brennstoffzellen. Da die leeren Packs (die immerhin noch 380 kg wiegen) die maximale Landenutzlast reduzieren kann das Raumlabor dann nur noch 6.5 t schwer sein.

It basically says, that one H2/O2 packet weighs 940 kg and for a 30 day mission, you would need 15.6 tons of H2/O2. And because the packets weigh 380 kg each empty, the payload for Spacelab is limited to 6.5 tons (because of the maximum landing weight).

And here is the part about the "symbiosis":

Das ist um so unverständlicher als das Space Shuttle ja anders eingesetzt wurde als geplant. konzipiert war er für den Aufbau und Versorgung einer Raumstation. Dann koppelt er bald nach dem Start an diese an und wird von ihr mit Strom versorgt. Die Raumstation wurde aber gestrichen, die NASA konnte sich nur ein Großprojekt leisten.

I believe he means Freedom with that.

Cheers,
Lunar_Lander

 

[Urwumpe]

Well, Bernd Leitenbergers view on manned spaceflight in general and his view on the space shuttle in special is pretty biased, so you should always be cautious with his argumentations. One H2/O2 package consists of two tanks- the dry weight of each tank (including heaters and valves) is ~100 kg, the oxygen stored inside is 360 kg, the hydrogen 42 kg. Makes: 602 kg per tank pair.

For a 30 day mission, the orbiter would need more tanks, than could be fitting, 16 tanks are already a hard job to fit.

Also, you can't just go by the pure power generation by weight (which is not favorable for solar cells anyway), but also, you have to look how it integrates into the spacecraft. The fuel cells are actually better for short manned missions, as they not only produce electrical power, but also a large supply of hot water, without requiring extra mass for heaters. That factor is indeed a large problem for the ISS - the Shuttle astronauts have some luxury in their kitchen, the ISS is still missing - they need to heat cold water electrically.

Leitenbergers argumentation about "That humans in space are pretty annoying", is more appealing as many of his technical criticism, which are often done from his point of view. His articles about unmanned missions are far better in quality as his manned mission stuff, and something you can indeed build great add-ons on.

EDIT: Also, only one orbiter is capable of mounting two EDO pallets (OV-105 Endeavor), which would allow it in theory to have 12 sets of tanks and a endurance of 27 days. Thats 7224 kg of EPS cryo storage, of which 4816 kg would be taken from the payload capability (the rest is fixed installation)

 

[Lunar_Lander]

Urwumpe, Thanks again for the STS info! Was your cookie good ?

Hmm, I hope the XR astronauts also have some hot water due to their reactor. Or at least any means of heating their food. Having to eat cold spinach * in Saturn's orbit isn't a really prospecting thought .

I think I'll now wait for Doug answering the remaining questions addessed at him. Also, he didn't fetch his cookie yet .

Cheers,
Lunar_Lander

*If you don't like spinach, enter your favourite food here .

PS: Doug, I hope the XR's temperature control works at all times. Right now I have 31°C and a felt temperature of 35°C (88 and 95°F). Wouldn't be really good for the crew to sit in the ship on the ground while havin to endure these temps. But I have to anyway *sighs*.

 

[dbeachy1]

I think I'll now wait for Doug answering the remaining questions addessed at him. Also, he didn't fetch his cookie yet .

My apologies, did I miss some questions? Can you be more specific?

 

[Lunar_Lander]

Hi Doug,

I mean the questions in post #422, the one with the cookie for you and Coolhand. .

Cheers,
Lunar_Lander

 

[RangerPL]

Hi Doug,
I have one question regarding the XR2 (sort of)

The XR2 already looks like a fine craft, but is a cargo version being planned? Something with a bay along the size of the Space Shuttle's bay. So it could fit, say 2 Leaonardo mplms.

 

[Master of Blades]

The XR2 already has quite of a Payload Bay... Think there are pics earlier in the thread...

 

[RangerPL]

The XR2 already has quite of a Payload Bay... Think there are pics earlier in the thread...

That's tiny compared to what the shuttle has... I was kind of hoping for something along the lines of a "futuristic space shuttle".

 

[Scrooge McDuck]

The XR2 already looks like a fine craft, but is a cargo version being planned? Something with a bay along the size of the Space Shuttle's bay. So it could fit, say 2 Leaonardo mplms.

Well, I think such a large payload bay you have in mind is rather unrealistic for the XR2 Ravenstar.
It's a completely different concept than the shuttle. I thought it's more a self-launching plane-like idea like the DG, so it needs much room for (lots of) fuel, electronics, etc.


But if you look much further into the future, when just a drop of fuel is needed to get into orbit, it could have a larger payload bay too (like the DG Cargo addon) . But then again, I think at that point in future a design like the XR2 isn't needed anymore..


regards,
mcduck

 

[dbeachy1]

That's tiny compared to what the shuttle has... I was kind of hoping for something along the lines of a "futuristic space shuttle".

Remember that the XR2's role is that of a "Luxury Learjet." Originally we didn't plan to give the XR2 any payload bay at all. In addition, slot #1 (the forward slot) will be (or should be) occupied by the CHM 99% of the time, so the payload capacity is limited. For large payloads, pilots can fly the XR5 or wait for the XR7.

I mean the questions in post #422, the one with the cookie for you and Coolhand. .

Ah, I had assumed all the other questions were rhetorical. Let's take them one-at-a-time:

What exactly is a Naquadah reactor ?

Naquadah is a fictional element that can be converted into a large amount of energy; the name is a homage to the Stargate television series. Details here.

I once asked you about an avanced EPS and you said it would be sopmething for an MkII release. I would really like to put my hands on the reactor controls (meltdown anyone ?)

An advanced EPS remains a possibility for an Mk II release; however, it will be awhile before I get to any Mk II releases because I have the XR2, XR7, and XR0 already in the pipeline. The only exception to this is the XR2 Mk II release, which will be the next project right after the XR2 Mk I release. The XR2 Mk II will include an active "touch-screen" virtual cockpit; however, that will be the only major feature being added. One of the keys to a successful software project is scope management: if scope grows too large the product is never released.

 

[willy88]

So will these payloads actually be functional (like how I suggested a few... hundred pages back), or will they just be "dummy" vessels that you can dock to?

 

[dbeachy1]

So will these payloads actually be functional (like how I suggested a few... hundred pages back), or will they just be "dummy" vessels that you can dock to?

To reiterate, all XR-class vessels that have a payload bay will use the same XR-class payload system. In other words, it will operate just like the Vanguard's payload system. This will be the case for the XR2 as well as all future XR-class vessels that have a payload bay.

 

[Coolhand]

I'm not sure if this is what you mean willy, but i did talk doug into the idea of making some payloads practical, so if you add a fuel module, or another consumable it will add to your total store of that consumable, extending the crafts range. Also the crew habitat module should extend your lifesupport capabilites -perhaps as a multiplier of your o2 level or lowering the rate of consumption or something.. i'm not sure if we discussed that, did we doug?

 

[Linguofreak]

XR-class vessels are powered by Naquadah reactors; solar power is not practical given the ships' power requirements and the requirement that XR vessels operate far from the sun.

Wait a sec.

If they have reactors, why do they need APU's?

Why not just use electrical power from the reactor to run control surfaces, etc? Or at least get their hydraulic pressure from a steam turbine feeding from the reactor?

 

[RangerPL]

(like the DG Cargo addon)

DG Cargo? Link pls (I searched OrbitHangar)

 

[TSPenguin]

Wait a sec.

If they have reactors, why do they need APU's?

Why not just use electrical power from the reactor to run control surfaces, etc? Or at least get their hydraulic pressure from a steam turbine feeding from the reactor?

Naquadah reaktors are very easily scalable in their output. Converting the energy output to different specifications is something completely different.
Also doing that would mean adjusting your power converter according to your current thrust, nasty stuff...

That is why doug just took one 12 pound generator on board and added some 100ish pound APUs. This way you don't have to attach half a mothership to the XR2 just to get some pressure in the pipes.

And just imagine it without the APUs!
What if the half mothership gets ripped of the XR2 on reentry? No control, you die, and everyone else within a few dozen kilometers.
The same is true in case of a reaktor failure. You just have a 50% chance of exploding right away.

But that is all completely irrelevant.
The APU is absolutely necessary because it has a

BIG RED BUTTON!
:woohoo:
:hitit:
​

P.S.: A few micrograms of naquadria in the nozzles before doing a vertical lift off replaces the SRB easily...

 

[tblaxland]

Naquadah reaktors are very easily scalable in their output. Converting the energy output to different specifications is something completely different.
Also doing that would mean adjusting your power converter according to your current thrust, nasty stuff...

Well, not such a big issue with modern power electronics.

I would suggest that it is more of an issue actuator size and optimising reactor utilisation. An electric actuator is many times larger than a hydraulic one for any given torque. In confined space such as wings this is very important. For a real world example, consider the Falkirk Wheel. It uses hydraulic motors for their compact size and the much larger electric motor that provides hydraulic pressure is located remotely.

This brings me to the second reason, reactor utilisation. Most non-linear electrical equipment tends to operate most efficiently at or near its design capacity. If the reactor was designed to also provide power to the control surface actuators it would need to be able to provide a lot more power than the normal base load. This would mean inefficient operation at base load levels.

But, as you say, it really is all about the big red button.