TheEpicSquared

July 18, 2017

The power to live but only when you're alive.

July 18, 2017

I don't know about White Lightning for the kick motor. The TWR will be through the roof nearing burnout, and our cubesat might not survive the forces.

We could pre-load the napalm in, but what about when we fill it up again for reuse? It would be difficult to cut the stage in half.

Also, have we decided on whether we're using a single-stick or quad-stick core?

July 18, 2017

July 16, 2017

Well, for the drag problem, if we could find an online wind tunnel simulator, which allowed us to make a model of our rocket, we could get relatively accurate drag models. However, it would be a pain to find a digital wind tunnel simulator...

Another thing I've been wondering about, how are we going to fill up the tanks? We could use the RCS thruster plumbing to pump in air and HTP, but loading the napalm could be a problem. We could load it through the nozzle, but space would be cramped to say the least.

What propellant would the kick motor be made of? We never really discussed it, IIRC.

July 16, 2017

Didn't do much in KSP itself, instead spent time modeling for a mod I'm planning:

That's an attempt for an inline Mk-55 Thud engine. Could definitely use some improvement. I think the throat is way too small, so that could use some improvement. Also, I'm using the online version of Sketchup, because it doesn't lag, unlike the desktop version, and I can access my designs from different laptops.

I'll export it to Blender for texturing. My mod will also include inline versions of popular radial parts, like RTGs and the Puff. Haven't thought of a name yet, but it probably will be something like InlineAdditions or something.

July 15, 2017

58 minutes ago, magnemoe said:

LOX is pretty common and also very dangerous.

Which is why it was ruled out in favor of HTP. :wink:

July 14, 2017

About the HTP issue. Whoever ends up doing this (if anyone) obviously have to get permission from the government, and clearly state their intentions: building and launching a PEACEFUL (i.e. not intentionally hostile to anyone) rocket into orbit. I'd say that they would have a little bit of wiggle room if an entity as large as a national government allowed them to push forward with this project. And I wouldn't be surprised if they got regular visits from organizations like the FBI and equivalents to make sure everything was going according to plan. Hell, the FBI checks in when farmers order large amounts of fertilizer to make sure they're not up to something, so I'd say that whoever does this (if anyone) should expect visits from the authorities frequently.

With the correct licensing (which will be a pain in the backside to get), it should be doable.

July 14, 2017

@Steel I think we're hoping for a 5 stick design (4 strap-ons and 1 core), but if that doesn't have enough Dv we are thinking of an 8 stick design (4 strap-ons and a quad-stick core). And I agree that it would be simpler to have pre-determined throttle settings. Maybe those could be deduced through testing. But does a micro-adjustable valve really cost that much? I searched "micro-adjustable valve" on google and a site came up selling a 5-pack for just $3.49. Granted, those are meant for garden sprinklers, but still...

When looking at @sevenperforce's spreadsheet (just the images posted, I haven't had time to download it yet), it looks like somewhere around 8km/s of Dv is the max, with favorable drag and gravity losses, fuel fractions, etc. If we can't find a way to optimize the design, a quad-stick core design seems the most viable. However, I'll download the spreadsheet when I can and play around with it.

July 13, 2017

I think we need to figure out the booster sep mechanism. As you all know, I'm in support of conventional explosive bolts, with a compressed spring up top to push it and the booster away. It's simple, it's been tried and tested, and it should be reliable.

Also, I shall reaffirm my liking with the name HYDRA, because of its mythological relevance as well as its relevant backronym.

July 13, 2017

@sevenperforce Your idea seems quite complex. What if the air-tight chamber isn't air-tight? What if the spring fails? What if the clamps themselves fail? It looks like there are too many failure points, IMO. A few simple explosive bolts with a spring up top seems more reliable.

@zeta function That's an interesting idea. It could work, and the airbrake could just be a curved piece of metal. However, it would have to be light, which would compromise its structural strength.

@sevenperforce That's one awesome spreadsheet! I, for one, would love playing around with it. Maybe transfer it to google sheets and upload it that way? And yeah, 10% throttle seems pretty low...

And I guess HYDRA is the name then? I don't mind, I like the backronym - HYbriD Rocket by Amateurs. And I like "Micropayload Orbital Vehicle":

HYDRA MpOV

July 13, 2017

No

@NSetser

July 13, 2017

Makes a bit more sense now, but pics would still be appreciated.

Hold on just a minute. Were we planning to have RCS thrusters on the core and strap-ons in the first place? I don't recall so, we said that we'd use differential throttling for control. From what I understand, RCS would only be on the second stage. If that's the case, it seems more complicated to add a single RCS thruster to the strap-on, and configure it to work as per @sevenperforce's idea. Opposed to just attaching a compressed spring to the strap-on and letting that push it away, I think my proposal seems easier to accomplish, and more reliable. It's only one component, versus @sevenperforce's several, which all need to go exactly right for separation to work.

@qzgy I think the reason we're not using hobby motors as separation motors is that we want to keep things as simple as possible, with as little ignitions as possible.

Also, @sevenperforce, how do you draw so symmetrically in MS Paint? I'm trying to make a diagram of what I'm thinking, but symmetry is hard.

July 13, 2017

@sevenperforce I don't really follow your separation idea. Diagram maybe? And about the chutes, I'm all for less chutes. If a reefed chute would work, then we'll go with that. Less mass is always good.

July 13, 2017

Could someone with a twitter account please ask Musk about the BulgariaSat-1 landing? I am getting impatient.

July 13, 2017

I agree with @qzgy - if we can still make orbit with higher than expected aerodynamic losses, we have some wiggle room and some room for error.

Here's some recovery ideas. I'm thinking drogues and then main(s), obviously. For the strap-ons, we could pack the chutes into the nosecone, like the Shuttle SRBs. However, it's a bit trickier with the core, since there is no nosecone space to pack the chutes into.

I say that we put the chutes near the rear of the core. This is because the core will be traveling quite fast on its parabolic trajectory, and having the chutes deploy from the front would require the stage to flip 180 degrees, which would put a lot of stress on both the stage and the chute itself. I'm pretty sure the stage would survive the stresses, but I'm not sure the chute (and the ropes that connect it to the stage) would. This wouldn't be as much of an issue with the strap-ons since they would be traveling much slower upon separation. And since pressure-fed hybrids are inherently much stronger than liquid or solid fueled rockets, we can just let them land on their sides.

Also, do we really need separation motors on the strap-ons? I have a spring-based idea, which would save a lot of mass and be simpler. We would use conventional explosive bolts as the primary separation mechanism, but we'd have a compressed spring at the top, attached to the strap-on and compressed against the core. When the explosive bolts release, there is nothing keeping the spring compressed, and it can un-compress, pushing away the strap-on to a safe distance without the use of a heavy separation motor. Then the strap-on can land on its own. The spring itself could be made out of any lightweight metal, like aluminum. Theoretically, even the springs in a car's suspension would work if they are not too heavy.

July 13, 2017

Cleaning up Debris

July 12, 2017

@sevenperforce How's that spreadsheet going?

July 12, 2017

8 minutes ago, sevenperforce said:

HEROS-3 is 7.5 meters long and 223 mm in diameter.

I'm going to go ahead and set up a cleaner version of the same spreadsheet I used yesterday, but factor in stepwise drag losses and allow for some deeper throttling, and tie it all to a single diameter multiplier. This will allow me to baseline total dV at a HEROS-3 equivalent size and then increase diameter gradually until we have enough dV to reach orbit. If I can't do it with a single-core I'll try again with a quad-core.

Could you share the spreadsheet here once you're finished?

9 minutes ago, sevenperforce said:

Interesting. Hydra would also be a neat name, since the base will have "many heads". Or we could call it the ARDYH since it's an upside-down Hydra...maybe backroynm that.

HYDRA: HYbriD Rocket by Amateurs

Could work

July 12, 2017

1 hour ago, sevenperforce said:

It should be easy enough to have a videocamera that stores high-quality video locally while simultaneously capturing still frames every few seconds and sending them back via VHF. This gives us nearly-live visuals but also preserves a video feed for later recovery.

Yeah, a video of the first stage core would be nice, and a camera that records and takes pictures simultaneously shouldn't be too difficult to get.

1 hour ago, sevenperforce said:

To clarify my earlier proposition: I was already working under the assumption that the second stage was a full-size single-stick core, so there's no extra dV to be gained there.

Ah, ok.

1 hour ago, sevenperforce said:

To a point, there are really no significant disadvantages in making the stages slightly wider; it doesn't make them significantly harder to handle, and the increase in drag is more than counterbalanced by the linear increase in propellant fraction.

The maths, in case anyone is curious:

Reveal hidden contents

Consider a hollow cylinder of length L and radius R. The weight of the metal skin making up the cylinder is proportional to the surface area of the cylinder, which is the circumference times the length, or 2*π*R*L. The propellant capacity of the cylinder is proportional to its volume, given by 2*π*R²*L.

If you increase the length of the cylinder (e.g., from L to 2L), then both the surface area and the propellant capacity increase together (surface area becomes 4*π*R*L and volume becomes 4*π*R²*L), with no change in propellant fraction.

However, if you increase the radius of the cylinder (e.g., from R to 2R), then the square term kicks in. The surface area doubles (4*π*R*L), but the volume quadruples: 2*π*(2R)²*L = 2*π*4*R²*L = 8*π*R²*L. So the ratio of propellant mass to container mass increases linearly with the increase of cylinder radius.

There's a slight increase in skin thickness in order to maintain structural integrity, but this is such a small value that it's negligible for relatively small increases in cylinder radius. And the increase in drag is also counterbalanced by the increase in overall vehicle weight. Another reason hobby rockets need high fineness ratios is that their low isp means their mass drops rapidly, but with our higher isp we hang on to our propellant for longer and so drag has less of an impact.

I think it will be much simpler to make a slightly wider stage than it would be to double or triple the number of first-stage cores.

Yeah, is also agree that making the stages wider is easier. That would increase the Dv by quite a bit, especially if we retain the quad-stick core with four single-stick strap-ons. I never really thought my 8 strap-on idea would be feasible anyways.

So, what type of diameter are we looking at? I know we're using the HEROS-3 as a base, does anyone know what the diameter is? From a picture, the diameter looks roughly 20cm, so ours could be slightly wider - 35 or 40cm?

5 minutes ago, sevenperforce said:

Oh, while we're at it...any ideas on a name?

A few possibilities:

Legion (since it uses clusters and parallel staging)

Jebediah (in honor of KSP)

EELOO (in honor of KSP, could backronym to something)

Kilgore (character in Apocalypse Now who delivers the famous line, "I love the smell of napalm in the morning")

I was thinking Chimera, because in mythology a Chimera was a mix of other animals, like our rocket uses a mix of different propellant types.

July 12, 2017

@sevenperforce

Maybe just two cameras on the center core would suffice. Using VHF, we could set the cameras to take pictures every X seconds, and relay them down to earth. This way we could visually confirm strap-on separation, and chute deployment, and finally landing.

About the center core, it seems better, in terms of Dv and TWR, to have a quad-stick core design, with single-stick strap-ons. The increased TWR would mean we could use a single-stick for the second stage as well (minus recovery hardware), instead of having to miniaturize the hardware for a second stage. Just make some modifications to the ablative nozzle and you'd be good to go. Control could again be maintained via the use of HTP RCS thrusters near the nozzle, and those same thrusters could be used for spin stabilization just before kick motor separation. I doubt that the longer second stage would push the Dv to 9.2km/s, but it would provide some excess Dv, which is always useful. We could make the tanks wider to hold more propellant, however this causes its own issues as discussed earlier.

One idea for raising Dv, which is... very kerbal, to say the least, is to use two quad-stick cores as strap-ons.

Actually, this equals to 8 single-sticks, so instead of having two quad-stick strap-ons (which would weigh a lot due to the structural attachments, and provide less control), we could have 8 single-stick strap-ons. Configuration is below:

A B

C D E F

G H I J

K L

So DEHI is the quad-stick core, and A, B, C, G, F, J, K and L are the 8 single-stick strap-ons. AB would be next to each other, as would CG, FJ, and KL. The throttling and staging would be the same.

This is getting on the complicated side now however.

EDIT: Picture for clarification (sorry that it's terrible, I drew it on my phone)

July 11, 2017

1 minute ago, PixelStory2 said:

That forum engine doesn't look very good. It sent me to a spam site that said I needed to update flash player when I clicked on one of the Sub-Forums. ._.

Odd. Didn't happen to me.

July 11, 2017

7 minutes ago, sevenperforce said:

On to the first/parallel stage(s).

Let's assume we use @TheEpicSquared's 1+2+2 configuration, with a core sustainer and two pairs of side boosters. GLOW is 1.5 tonnes. Determining when to throttle down and how far to throttle down is itself a major optimization problem, but let's start by assuming the following sequence, just to get ballpark performance:

Launch: core at 100%, booster pair A at 100%, booster pair B at 100%

25% propellant consumption: core at 50%, booster pair A at 50%, booster pair B at 100%

Booster pair B burnout: separation, core at 50%, booster pair A at 100%

Booster pair A burnout: separation, core at 100%

At this rate, we should expect to get 336 m/s from launch to throttledown, 817 m/s from throttledown to booster pair A burnout, 471 m/s from booster pair A burnout to booster pair B burnout, and 245 m/s remaining on the core, for a total of 1.87 km/s off the first stage. Now, the sooner we can downthrottle and the deeper we can downthrottle, the better, but TWR will become an issue if we downthrottle too low or too early. Combustion instability is also a reason not to downthrottle too aggressively.

With 1.87 km/s for the parallel/staggered first stage and 5.655 km/s for the second stage and kick stage, we're already up to 7.52 km/s, which is DEFINITELY in the neighborhood of orbital flight. Of course, we have to subtract out gravity, pressure, and drag losses. But it's certainly in the right ballpark. And there's nothing saying we can't make a slightly wider stage than HELOS-3 and pack more propellant in, especially because we don't need the ultra-extreme fineness ratio typical of low-isp, high-thrust amateur rockets (amateur rockets make up in part for their poor isp by their very high thrust, cutting down on gravity drag but necessitating an ultra-streamlined profile to minimize more significant aerodrag losses).

If our final design is generally in this ballpark, we can also get an idea of the minimum thrust rating we'll need in order to make it all work. In this configuration, the lowest TWR condition is at secondary booster burnout, when the core is lifting its own partially-fueled mass plus the mass of the upper stage, kick stage, and payload. In order to ensure sufficient TWR at this point in the ascent, I would suggest that an entirely full core ought to be able to lift an upper stage, a kick stage, and the payload with no less than a 2:1 TWR. Crunching the numbers, this means a naked stage TWR at least 4.4 and a single-motor thrust of at least 10.5 kN, about the same as the HELOS-3. Launch TWR would be 4.56:1, and hybrid-stage mass flow at 100% is 3.57 kg/s with a burn time of 47.3 seconds at full throttle.

@sevenperforce Mind telling me what GLOW is? Also, how do you get those numbers? Could you tell me the formulas you use?

This second stage would also be hybrid, using our HTP+napalm configuration, yes? In this case, what would be the relative size of the first and second stages? Purely guessing here, I'd say that it would have to be around the same size or just a bit smaller than the first stage, since it still has to produce the majority of the 5.655km/s of Dv, but it's already high in the sky which reduces gravity and aerodrag losses. It would also be lighter than the first stage, since we could eliminate the chutes and their deployment system, saving mass. The RCS could go at the bottom, so it would be far away from the center of mass (which would be closer to the top of the stage due to the kick motor+payload). Just before burnout, the small amount of remaining HTP could be redirected to the RCS system to spin up the rocket for spin stabilization during the kick motor burn.

Also, what type of communication would we use? From the KSP Community CubeSat thread, S-Band seems ridiculously expensive, so it seems like VHF is the way to go. Unless we want a live feed of our rocket going up, I don't think an S-Band system is necessary. VHF can still take pictures, in the event that we would want cameras on the rocket. Speaking of which, are onboard cameras really necessary? I'm against it for rockets this small, since the weight of a camera makes up a lot more of the entire rocket's mass with a small rocket than with a big one. And we'd get all the telemetry we'd need anyway, so we don't need visual confirmation, IMO.

July 11, 2017

4 hours ago, Uace24 said:

Any updates on the new fourm page

Progress is being made, more info below

4 hours ago, Skylon said:

Now I was originally thinking that the forums would just be for this specific mission idea, but I understand that other groups could use it as well for role playing their own companies. Is that planned?

Not at the moment. However, if demand increases, it is possible to expand the forum to include other ideas. That won't be for a while, though. BEst to focus on ours first to make sure it's top-notch.

UPDATE

So, progress is being made on the forum. Here's the link (note that it's in extremely preliminary stages) http://ksp-rtsi.forumotion.eu/

So far, we've got the General Rules up. That's about it, although there's a lot in planning. What we need help with now is the structure of the forum. This is what we have so far, suggestions welcome:

Format:

Forum

General Section 1 (equivalent to "General")
   Section 1 (equivalent to "Announcements")
Thread 1
   Thread 2
   etc.
   Section 2 (equivalent to "The Daily Kerbal")
   Thread 1
   Thread 2
   etc.

General Section 2 (equivalent to "General KSP")
   Section 1 (equivalent to "KSP Discussion")
   Thread 1
   Thread 2
etc.
   Section 2 (equivalent to "Suggestions & Development Discussion")
   Thread 1
   Thread 2
etc.
  etc.

So here's the currently planned format:

KSP - Recreating the Space Industry

Rules & Information
   Rules
   General Rules
Participation Rules
   Information
   General Information about the Mission Idea
   Useful Links

   Announcements
General Forum Announcements
   Thread 1
   Thread 2
etc.
   Mission Idea Announcements
   Thread 1
   Thread 2
etc.

Company Registration
   Payload Company Registrations
   Payload Company 1's registration thread
   Payload Company 2's registration thread
etc.
     Launch Company Registrations
   Launch Company 1's registration thread
   Launch Company 2's registration thread
etc.

   Lists
   List of Payload Companies
   List of Payload Companies
   List of Launch Companies
   List of Launch Companies

Craft Submissions
   Payload Submissions
   Company 1's thread
   Company 2's thread
etc.
   Launch Vehicle Submissions
   Company 1's thread
   Company 2's thread
etc.

Launch Contract Negotiations
   Launch Contract Negotiations
   Contract negotiation 1
   Contract negotiation 2
etc.
   Finalized Launch Deals
   Launch deal 1
   Launch deal 2
etc.

   Launches and Savefile
Launch Coverage
   Launch 1
   Launch 2
etc.
Savefile (Current Time of Save: Year X Day Y HH:MM:SS)
   Savefile: Date X
   Savefile: Date Y
   etc.

   Addons Used
   List of Addons
   List of Addons
   Addon Suggestions
Addon Suggestions

   Suggestions
   General Suggestions for Forum
   Thread 1
   Thread 2
etc.
   Mission Idea Suggestions
   Thread 1
   Thread 2
etc.

Off-topic
   Science & Spaceflight
   Thread 1
   Thread 2
etc.
   Other Off-topic discussions
   Thread 1
   Thread 2
etc.

So yeah, that's the very preliminary plan. Feedback and suggestions are highly welcome and encouraged.

July 11, 2017

@sevenperforce If RWs don't work, would magnetorquers be too small? And another thing, I just realized that we most likely will not be able to recover the center core, considering that it is being accelerated to nearly orbital velocities.

Also, it wouldn't be that difficult (relatively speaking, of course) to just add another strap-on, if 3 aren't enough. In fact, I think this would be better since now you have direct control over each direction, left, right, forward and backward. This is better than a 3 strap-on variant, which would require multiple cores to throttle down to get the same four-directional control.

Assuming this configuration, I have a rather complicated idea for throttling and staging.

If A, B, C, D and E are the cores, then looking at the rocket from the bottom would result in this view:

A

B C D

E

If thrust allows, I say that shortly after liftoff, cores B and D stay at full thrust while cores A and E throttle down to 75%. Core C, the sustainer, throttles down to 50% thrust.

Because B and D are running at a higher thrust, they separate first. At this point, A and E throttle back up to 100% until they burn out, with C remaining at 50% thrust. When A and E burn out and separate, C would throttle back up to 100% until burnout and separation, at which point the kick motor would fire at apoapsis and complete orbit.

July 10, 2017

@sevenperforce

About the valves, wouldn't having 7 valves+piping significantly increase mass, and cost as well? Legitimate question, does a finely-moving valve really cost that much?

If it does, then I'd say reducing the number of valves from 7 to 4. One in the middle with theee around. This gives us 25% throttle increments, so we'd have 25% (if possible), 50%, 75% and 100%. That seems good, I'd say. The strap-ons would fire at 100% while the sustainer would throttle down to 50% or even 25% if that deep throttling is possible.

Your air augmentation idea seems nice, but I'd have to agree with @qzgy, it does seem to be quite difficult.

Also, do you use MS Paint for your diagrams?

@mikegarrison I think by "amateur" we mean "an educated guy who doesn't have a few million / billion to invest in a rocket or three". :wink:

So, I guess the basic design is a 4-core design, with 3 strap-ons and 1 sustainer, possibly with a solid kick motor for final orbital insertion. This configuration seems ideal. We could use differential throttling for control until strap-on jettison, at which point we could start using the HTP monopropellant RCS system.

I'm also thinking, in the event of a kick motor, an RCS system would take up a lot of mass. How feasible would a system of reaction wheels be? After all, with a ~3kg payload, the kick motor could be quite small. Since the motor only needs to be used for a short period of time, de-spinning the wheels would not be necessary. The wheels themselves wouldn't need to be that big, given the low mass of the motor+payload. Also, we could orient the craft to release the payload facing a certain way, if necessary.

Another thing, as per @sevenperforce's idea of having the HTP tank integrated into what would be the combustion chamber, what type of length reduction and diameter increase are we looking at? Decreased length always is a good thing, obviously, but a wider rocket body of course means more drag.

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