Potential Problems With X-37 Testing by NASA?

By Keith Cowing
June 1, 2003
Filed under ,
Potential Problems With X-37 Testing by NASA?

From someone@nasa.gov

Dear NASA Watch:

Have a look at the attached slides (all references to briefing dates
presenters etc is taken off). B-52 separation issues have
plagued the X-37 program from the start – and Susan Turner and Jeff Sexton have
simply tried to “wish the problem away”.

The vehicle just flies too well at the B-52 drop speeds and we
have to install a drogue chute to prevent “recontact” after launch. We
briefed Marshall on this 3 years! ago. We convinced Boeing of this
necessity and got the go ahead to proceed with systems development.

As you can imagine, this soon became a Boeing/DFRC-only development
due to the fact that no one on the MSFC X-37 team has the slightest
technical competence.

Download 6 MB Powerpoint file

Well, as we achieved progress – and are almost ready to start testing – MSFC got worried that they are going to look bad and ordered a “stop work” on this

“We are going to launch it from a hellcopter (see below) from Vandenburg and we
don’t need you guys and your B-52”

A Helo? 42k ft? How? The launch speed is 95 knots below the stall speed of
the X-37 – it’ll drop like a rock. “We don’t care, you are impacting
our schedule.”

As you can immagine this is the tip of the iceberg these
problems happen over and over and over again …


  • Issues relating to software and hardware integration and testing are not significantly changed by the realignment to a helicopter drop. These tasks are assuredly driving the project schedule.
  • The number and variety of new helicopter related tasks would add to the schedule in many areas. We believe that the schedule savings are imaginary and most likely would be negative. The current design is far along and has everyone focused. The new plan call for a total change in focus that effects almost every discipline on the program, brings in new team members that have not had an opportunity to weigh-in (Ft. Rucker, Vandenberg), and includes significant unknowns in helicopter performance and integration.
  • Objectives

  • In our opinion, adequate in flight testing of GN&C requires exercise of the HAC and energy management algorithms. The helicopter will not significantly add to the knowledge base on these critical technologies over what has already been accomplished on the X-40.
  • The CADS calibration will vary with flight conditions. The short, low Mach flight testing will not adequately calibrate the system over the critical HAC and approach and landing phases of the trajectory. Since the helicopter tests involve straight in trajectories, the angle of attack variation will be minimal. CADS calibration can be significantly effected by flow separation over any port. Very little additional data will be obtained with respect to the X-40 program. Can we go to an OV without validating the CADS calibration methods above M=0.2? A calibration at M=0.7 may help us find issues that will become more difficult in the transonic Mach region. The CADS system deserves flight validation.
  • Though the aerodynamics of the vehicle do not change dramatically from M=0.2 to 0.7, there are differences that should be quantified. We have already made some attempt to flight validate the low speed aerodynamics of the X-40. How would a low speed X-37 significantly different that what we have accomplished on the X-40?
  • B-52 Integration

  • Integration of a launch vehicle on the B-52 is not simple. The operation is at high altitude, Mach number, and dynamic pressure that stresses a launch vehicle beyond a simple moderate altitude, slow speed launch. However, this is the reason that the B-52 was selected in the first place. The X-37 will be subjected to harsh environments and high dynamic pressures. The B-52 allows us to fulfill our responsibility of testing the vehicle and systems as much as possible before the orbiter launch.
  • The B-52 issues are mostly resolved and few are on the critical path. Operation below the vehicle opens up many new issues and design changes. These changes are orders of magnitude more difficult than current complaints about adding a chute jettison capability (2 wires) or quantifying sideslip.
  • Helicopter Integration

  • There are many hazards involved with the helicopter integration. Ground lift-off and touchdown are clear risks to ground personnel and the X-37 itself.
  • The helicopter trade study refers to several options for mitigating risk for the helicopter touchdown. One was landing gear redesign. Obviously this is a cost and schedule unknown. When would the new gear be manufactured and ready to install? Another option is airbags deployed for touchdown. How can anyone complain about the cost of the drogue chute (which is mostly being accomplished outside of Boeing) and then bring up this idea?
  • The X-37 does not have sufficient battery power for the mission without external power during captive carry. It is not clear that this power is available or how difficult it will be add it. The potential for significant modifications to a military asset may add more complexity than is currently envisioned.
  • The helicopter concept plans to operate outside the current envelope of the vehicle. A weight reduction method was cited but no evidence is available on viability.
  • The helicopter trade study states that software modifications for the change are off the critical path. These tasks and the requirements changes that go with them are not defined. When has flight software not been on the critical path?
  • The helicopter trade study states that relay logic hardware changes are minimal cost and not on the critical path. We have been told dozens of times by Boeing avionics engineers that these items were on the critical path and that any change would be a significant cost impact.
  • Boeing GN&C has repeatedly stated concerns about launching if the B-52 sideslip is greater than 1 degree. What is the new helicopter requirement? One degree will be impossible to enforce with the hanging vehicle below a helicopter.
  • Vandenberg

  • Flights at Vandenberg present new Ec issues. There are population centers at the end of the runway that is aligned with the prevailing winds.
  • Closing comments and recommendations

    The X-37 program is not easy. If it were, we shouldn’t be wasting the taxpayers money doing it. Taking what the program has done to date and realigning it into an essential repeat of the X-40 program begs for criticism from inside and outside of the aerospace community. It’s a baby step. How will NASA claim that we are blazing new ground for the tens of millions of dollars spent? Is NASA prepared for the criticism that Congress and OMB will give to the proposed change? Can we state that we are aggressively developing technologies for an Orbital Space Plane? If the X-37 program as currently defined is too difficult, too time consuming, or to distracting from the goal of launching an orbital vehicle, then the X-37 ALTV should be discontinued and the resources realigned with the Orbital Vehicle.

    SpaceRef co-founder, Explorers Club Fellow, ex-NASA, Away Teams, Journalist, Space & Astrobiology, Lapsed climber.