Student contest for designing a 10t payload Mars Lander

[sevenperforce]

On 2/14/2018 at 2:58 PM, KG3 said:

So what happens when you fire an engine to slow your craft down from a super sonic speed?  I'm thinking like when the first stage of a Falcon 9 reenters the atmosphere.  Does the exhaust distort or even punch through this bow shock or somehow become part of the boundary layer around the rocket?  Can they even fire the engines into a super sonic head wind or do those waffle fins slow it down to subsonic first?  I just ask because I've read there is some consideration of atmospheric pressure when it comes to rocket nozzle design.    

Supersonic retropropulsion is one of the technologies which SpaceX specifically wanted to test using Falcon 9 for Mars landing applications. If I recall correctly, they even partnered with NASA for some of the research on that....

https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20170008725.pdf

There we go. SpaceX gave NASA their data on supersonic retropropulsion so they could produce papers like these. If I were you, I'd cite the hell out of that paper if your proposal involves supersonic retropropulsion in any sense.

[KG3]

1 hour ago, sevenperforce said:

There we go. SpaceX gave NASA their data on supersonic retropropulsion so they could produce papers like these. If I were you, I'd cite the hell out of that paper if your proposal involves supersonic retropropulsion in any sense.

Wow, thanks for posting this paper!  I guess this paragraph says it all.

"Mission Infusion Potential: Propulsion is the only Mars entry, descent and landing technology that is intrinsically scalable across a wide range of missions. While not explicitly required for today’s robotic science missions, one can envision the potential use of supersonic retropropulsion on a next decade robotic Mars mission in an architecture that accommodates significant propellant mass or as a robotic precursor to eventual human Mars exploration. Architecture-level parametric assessments have demonstrated that SRP is likely required to enable safe landing of Mars landed payload masses above approximately 5 t. As a result of the large gap between current capability (payload mass of approximately 1 t) and that needed for
Mars human exploration missions (payload mass above 20 t), a progression of analysis and flight testing is required to mature SRP into a viable capability ready for infusion into a human exploration mission."

Are they saying in this paper that supersonic retropropulsion (SRP) should exclude the use of heat shields and parachutes for Mars landings above 5 t? 

[sevenperforce]

24 minutes ago, KG3 said:

Wow, thanks for posting this paper!  I guess this paragraph says it all.

"Mission Infusion Potential: Propulsion is the only Mars entry, descent and landing technology that is intrinsically scalable across a wide range of missions. While not explicitly required for today’s robotic science missions, one can envision the potential use of supersonic retropropulsion on a next decade robotic Mars mission in an architecture that accommodates significant propellant mass or as a robotic precursor to eventual human Mars exploration. Architecture-level parametric assessments have demonstrated that SRP is likely required to enable safe landing of Mars landed payload masses above approximately 5 t. As a result of the large gap between current capability (payload mass of approximately 1 t) and that needed for
Mars human exploration missions (payload mass above 20 t), a progression of analysis and flight testing is required to mature SRP into a viable capability ready for infusion into a human exploration mission."

Are they saying in this paper that supersonic retropropulsion (SRP) should exclude the use of heat shields and parachutes for Mars landings above 5 t? 

No, they are saying that heat shields and parachutes alone are not sufficient to land payloads above 5 tonnes. 

[KG3]

12 hours ago, sevenperforce said:

No, they are saying that heat shields and parachutes alone are not sufficient to land payloads above 5 tonnes. 

It seems like the article doesn't speculate much on engine or nozzle design.  I wonder how a aerospike engine might work at this? 

 "Propulsion: Engine bell stiffness and structural dynamics, induced by interactions with the flow before engine start, followed by reverse pressure after start are areas needing further characterization. Severe variation in the pressure environment may drive structural dynamics. If an SRP engine configuration includes embedded engines, heat rejection could also be a challenge. For SRP configurations utilizing the same engines for both high thrust maneuvers and soft landing, deep throttling and thrust vector control may be required beyond the current state-of-the art to provide a low velocity landing and prevent site alteration at landing." 

[sevenperforce]

On 2/16/2018 at 8:11 AM, KG3 said:

It seems like the article doesn't speculate much on engine or nozzle design.  I wonder how a aerospike engine might work at this? 

 "Propulsion: Engine bell stiffness and structural dynamics, induced by interactions with the flow before engine start, followed by reverse pressure after start are areas needing further characterization. Severe variation in the pressure environment may drive structural dynamics. If an SRP engine configuration includes embedded engines, heat rejection could also be a challenge. For SRP configurations utilizing the same engines for both high thrust maneuvers and soft landing, deep throttling and thrust vector control may be required beyond the current state-of-the art to provide a low velocity landing and prevent site alteration at landing." 

Aerospikes would be useful. A plug nozzle is good, too. Draggy.

Another way to make a stand-out entry would be to advance a different entry and descent approach than standard heat shield. One problem with an inflatable heat shield is that it's not inherently stable; if you play with them in KSP, you know how easy they are to flip. What if you could use that to your advantage? Instead of an inflatable heat shield, suppose you advance a deployable rigid heat shield that comprises two triangular panels, forming (in essence) a glider shape.

For high-altitude entry, you could have a passively stable configuration that would become progressively more unstable as the atmosphere thickened. Finally, the whole thing would flip, after peak heating, and it would look like an ultralight airfoil for guided descent. Then it would jettison and you would land propulsively.

[Jirokoh]

Hello !

Just a little update for you guys, just to tell you what designed we started to take:

So the basic idea was to make a lander that can put a 10t payload on Mars. But, we decided to see what we could do with a Falcon Heavy, because it's basically FH or SLS, and SLS is much, much more expensive than FH. Keep in mind that for the contest, we need to be able to design, build and launch by 2026. Since money is also a big factor in this contest, we decided to have two configurations :

- FH launched lander which can put (rouglhy) 6.4t on Mars. That's not 10t, but we can send multiple ones, for the same cost of one SLS launch (and we are sure we can send it by 2026, because well SLS is... let's say delayed...  )
 

- SLS launched lander, that can put the 10t payload, which would be used for the manned missions, as well as all the payloads that would be in one block (the biggest crew modules for example)
 

Let's get the big one out of the way: the SLS one is going to be pretty simple, just like most landers up to now: big heat shield, and big retro rockets at the end.

The most interesting part is the FH one: FH can send up to 16.8t towards Mars, so that means we have to take mass down as much as possible, while using current technologies, no fancy warp drive, or Kerbal nuclear reactor.
So our idea is rather simple, as mentionned earlier, we are going to do an aerobraking, to save as much DeltaV as possible, and thus as much mass as possible. This makes the mission last a long time (and this is why we are not going to do it for crewed missions, let's not let real life Jebs stay for months and months aerobrake around Mars)

We tried this, and the results are pretty good actually. First of all, thuis is our what our module looks like:

You'll notcie that the mass is slightly above 16.8t, but since we don't have the exact mass distributions, and more DeltaV than we are actually going to have, that's not a big issue. Same goes for simensions, our lander is going to fit in the 5.4m diameter fairing of the FH.

So this is to get a basic idea, and what we did is use a whole bunch of mods (maybe too much actually), but the aim is to use RSS and RO to have the most accurate modelling possible.
By the way, does any of you know which mod we could use to have the best Mars atmospheric models for our simulation purposes?
Because we can have a loooot of info with KSP, as you can see (and probably already know):

 

 

Here we are at about 79km, at our periastre, and the aim is to lower the apoastre by doing multiple paths. But since we want to be pretty accurate, we are using data provided by KSP to get the ballistic coefficient, as well as drag information, to use another software, to modelize Martian atmosphere re-entry.
The thing is, drag (and thus ballistic coefficient) change depending on the Reynolds number, or the flow around the spacecraft. But our re-entry software doesn't take that into account, so we used an avergae value, by doing multiple passes with KSP.
This is why we want the most accurate simulation possible with KSP.

Actually, we are also working on Ansys to make a CFD model of our lander, to more accurately get those drag, lift and ballistic coefficient. By the way, if someone can provide help with that, please get in touch!

Just to give you an idea of the result withour software, this is the type of things we can get:

Oh, we are French by the way... 

So on the left we have altitude depending on time, and right thermal fluw depending on time. These parameters are given for a 12t lander (this is after having done our elliptic insertion burn), with a ballistic coefficient of 600, for an orbit that has Apo=1000km and Peri=80km (the thing is, this software was designed by someone I got in touch with that works at CNES (French space agency), but it's in no way a finished software, so if we try to simulate an orbit with a Apoastre of 15,000km, the thing crashes; there must be an inside Kraken build in too...)

So, have some pretty good data up to now, this was just to let you guys know a little bit what we are up to

 

But we also have a lot of questions: 
- What's the best mod for modelling the atmosphere of Mars
- What are the limits of such modelisation (because this is where it makes our project be credible, if we use something, it's important to tell what are the limits of our simulations, and what impact that has)
- It seems the ballistic coefficient has a very big influence on the trajectory of the lander, but we do not fully understand why it is so import, if someone has some explanation (with solid evidence like always, would be even better)
- Why the hell did we even try doing such a project in the first place? Because... deadline is 31rst of March 

 

Thanks for reading, helping and being interested

Edited March 16, 2018 by Jirokoh
Kraken came in and changed things